Damp Wall historic buildings photo

On 21st November 2019, the ‘Agreed Methodology for Assessing Damp in Traditional Buildings’ was launched.

As our partner, Stephen Boniface, discussed in previous articles, for many years traditional buildings, many of which are Listed Buildings, have been damaged by remedial ‘damp-proofing’. Often this will start at the mortgage valuation stage with the valuation report requiring a ‘timber and damp report’. We also see many surveyors recommend a ‘specialist damp inspection’ as part of a building survey report for a home-buyer. Such inspections are often done for free, or very low cost, and will contain a quotation for remedial repairs that might be many thousands of pounds.

In the case of Listed Buildings, it would be rare that Listed Building Consent would be granted for such works, but we often see work done without consent. Once a wall has been treated, it cannot be reversed.

In response to what has become a cultural practice for many within the industry, the new Agreed Methodology seeks to address these problems. This Document is currently a working draft and there is a way to go before it will be formally adopted.

RICS have said..

“RICS has been working with Historic England and the Property Care Association to create a methodology centred around investigating moisture related issues in buildings. The aim of this initiative is to draw wider awareness to the issues that can occur in traditional buildings if the correct damp inspection principles are not followed, and to raise the bar in the investigation and reporting of moisture related problems in our built environment. RICS supports this initiative and will be consulting with its members and wider industry on a draft methodology that has been produced following a series of discussions between the organisations”.

Ultimately, the aim is to provide a holistic assessment of any form of moisture within traditional buildings and the possible consequences of that moisture. It seeks to unify best practice within the entire profession and to ultimately stop mistakes being made, misdiagnosis, buildings unnecessarily damaged and providing consumer confidence in the reports that are provided.

Over the next few years we will see an increase in awareness, professional training and changes made to reporting of moisture issues. We expect to see the Agreed Methodology formally adopted and instilled into Regulations of the professional bodies so that surveyors and contractors will be held accountable for their advice and actions.

RICS has also recently released the new RICS Home Survey Standard. This will further reinforce the raising of professional standards of building survey report.

Stephen Boniface is pleased to have been involved in the drafting of this document with others on the RICS team being: Craig Ross (for RICS), Duncan Philips, Mike Parrett, John Edwards, David Watt and Peter Ward.

Click here to download the document…

 

Damp Wall historic buildings photo

In this post, Chartered Surveyor Stephen Boniface gives his advice on rising damp and how it is often misdiagnosed.

Damp tide mark

Many years ago I was asked to present a talk on dampness and I discovered that my talk was to be the first one after lunch.  This is often known as ‘the graveyard slot’ because after lunch one feels rather tired and it is not unknown for delegates to drop off during the talk.  I thought that it might be useful to wake them up with a controversial opening statement. I therefore declared “there is no such thing as rising damp”. I then went on to explain my views and in fact said much of what is to follow in this article.  Nonetheless, I became known quite quickly as the building surveyor who does not believe in rising damp. To add to this a friend of mine in the professional world is Jeff Howell who once wrote a book called ‘The Rising Damp Myth’. Jeff and I once produced a training video discussing the issue.  Apart from setting the record straight for my part in this article it is important that the issue of rising damp is understood. Bear in mind that most buildings I deal with are historic and, as discussed later, they are technically different to most modern buildings.

What is dampness?

In the UK dampness is a major problem; brought about largely by our climate.  It is perhaps the one thing that most property owners are most concerned about.  This is quite understandable and is indeed a reasonable concern as dampness can cause a lot of damage to buildings.

However, there are many forms of dampness and of course many causes.  The one that causes most concern for a purchaser or home owner is rising damp. Nonetheless, I would argue that rising damp is perhaps the most commonly misdiagnosed form of damp. And yet, in my experience rising damp is probably the rarest form of damp whilst condensation is probably the most common (although perhaps the least well understood).    

Dampness means an excess amount of moisture.  Note the use of the word ‘excess’ because most materials require a level of moisture otherwise they become desiccated.  A certain amount of moisture in a material is not necessarily harmful. Indeed, for most building materials moisture becomes harmful when it has built up to such a level that it becomes manifest in some way, through smell or visually, or even causing physical damage.  Of course, the assessment of damp should not rely purely on such tangible evidence, but without such evidence one must question the seriousness of the moisture level, if the only ‘evidence’ is a reading from a moisture meter.

There is of course the possibility that moisture is gradually building up and at one point in time there will be no physical evidence and yet a short while later the evidence could appear.  Anyone assessing moisture in a building must be aware that moisture levels will change and a reading at any one time can be misleading. Here a proper understanding of other issues is necessary for a full and proper understanding of what moisture is doing within a building.

Assessing dampness

For many years now we have used a moisture meter to help detect moisture levels.  Used carefully and intelligently this can be a useful diagnosis tool. Unfortunately, it is often misused, and its limitations are not fully considered by those using it.  

There are many surveyors who, if a moisture meter gives a reading, recommend a further specialist investigation and report.  Depending on the level of survey being undertaken this might be appropriate because for certain types of inspection it is not the surveyor’s role to diagnose the problem.  However, there are times when one would expect the surveyor to undertake a full diagnosis and not refer the matter on for further investigation etc.

Indeed, this is where the misdiagnosis (or perhaps unwillingness to diagnose) often arises and causes problems.  Surveyors obtain a reading and then request a specialist report with that report then prepared by a company whose primary function is to undertake specialist treatments.  Although that company’s surveyors may be trained to diagnose damp problems, they are first and foremost sales people. They have a vested interest in finding a damp problem that they can then treat; for some working on a commission basis it is the difference between earning a decent wage or not.  This then leads to work that, in my opinion, is often unnecessary and therefore a waste of the clients’ money.

The problem is compounded by the fact that surveyors and other professionals have to undergo something called ‘Continuing Professional Development’.  They have to demonstrate to their professional bodies that they have undertaken studies (perhaps attended courses) covered a certain number of hours of CPD each year.  A number of specialist treatment companies offer free CPD to surveying companies, etc. On the face of it this may seem very helpful but of course the companies are there to sell a product.  Many surveyors rely on such CPD for their dampness training and it is therefore no wonder that these surveyors automatically think that if they obtain a reading on their meters then they should refer the matter on to one of these treatment companies.  

To compound the problem further many mortgage valuers are required to use certain phrases when completing valuation reports.  If they find evidence of, or suspect, a damp problem they are often required to refer the matter for specialist investigation.  The mortgage companies usually require that such investigations be undertaken by a company belonging to the Property Care Association (PCA). Most (not all) of PCA’s members are treatment companies.

There are many good surveyors and other professionals out there who are not members of PCA and yet are perfectly competent at properly assessing dampness and do not have a vested interest in any specialist treatment.  Of course, some members of PCA do offer impartial advice as not all are reliant on selling a particular treatment. You may also find that some of the treatment companies might be persuaded to provide impartial advice if paid to do so.

What is rising damp?

I have so far discussed the problem of why dampness, specifically rising damp, is often misdiagnosed; through ignorance and vested interests in a certain approach. So, let me now consider the matter of rising damp.

Many materials we construct buildings with are to some extent porous and/or permeable, thus allowing moisture to enter the material.  Such materials (brick, stone, mortar, etc.,) will therefore contain moisture. The argument for rising damp is that these materials absorb moisture from the ground and that it then gradually builds up and continues to rise up the wall until it becomes a problem.  It follows that the logical treatment for this is to insert a horizontal barrier, hence the need for chemical treatment as a retrospective remedial measure. This assumes that once a material has absorbed moisture it will not release it and therefore the level of moisture gradually increases to eventually become a damp problem.  

However, with most building materials they will not only absorb a degree of moisture but will also release it.  Unless the material is continuously wet then the level of moisture will ebb and flow, as the material sometimes wets up and then for periods will dry out as the moisture is released.  It follows that the base of a wall might be damp on occasions but will dry again and the moisture never actually builds up sufficiently to ‘rise’ up the wall.

Another argument for rising damp is that there is a form of pressure behind the moisture thus keeping it in the wall and forcing it up the wall. However, one only has to look at many moated historic buildings to realise that water will only rise a certain level before it evaporates from the surfaces.  If you look at any flooded area the tidemark of the water is not often more than a few centimetres, perhaps 300mm or thereabouts, above the level of the water.  Our ancestors knew what they were doing when they constructed houses whereby the ground floor was raised up and you walked up steps into it. If the ground floor is high enough above the zone likely to become damp then there is in fact no need for a damp-proof course, because the damp should never reach high enough to cause a problem.

If a wall has no cladding or other finish to it the moisture can freely evaporate from the wall material.  The moisture will accumulate at the base of the wall and will appear to rise as it accumulates. However, if it can evaporate from those surfaces there will come a point where the rate of evaporation from the wall is greater than the rate of uptake.  This zone creates what we often call a tidemark on the wall. Under normal circumstances in a conventional 9” thick wall this damp zone is usually only in the bottom couple of courses – perhaps 6-inches (150 mm). This is why, in the late 19th century, the Victorians required houses to be built with a physical damp proof course two courses of brickwork above ground level.  They knew that this was approximately where dampness would naturally evaporate out; the damp proof course was there as a secondary barrier to ensure that if moisture did not evaporate quick enough and tried to rise slightly higher it would not cause an internal problem.  Therefore, it seems that, from observation logic and understanding of buildings, one can see that true rising damp will only usually occur in the bottom couple of courses of brickwork.

Taking steps to prevent damp

Of course, there are situations that affect the risk of damp being a problem in the first instance.  A building constructed in a valley on impermeable soils could find itself sitting in a moist situation for much of the time.  In these situations, it is far more likely that the walls will never fully dry out at the base and there is a greater risk that moisture could find a way of rising further up the wall.  However, a building constructed on a very permeable subsoil or on the top of a hill will very rarely have water sitting under it for any great length of time because the ground water will naturally flow away from the building meaning that the walls are not generally sitting in damp soil and are unlikely to become excessively damp anyway.  

Where one has a damp wall, one must first consider whether the wall is likely to be in a damp location, be sitting in a wet soil, or in some way exposed to an excessive amount of ground moisture that could then be contained within the base of the wall.  Over the years I have come across such situations but have found that careful installation of ground drainage and external channels can divert ground water such that the building itself does not remain excessively damp.

A common problem is where walls have been coated over the years with render or perhaps other impermeable finishes externally and sometimes by impermeable finishes internally.  Another frequent problem is that the ground level externally has been increased such that the ground against the building is high in relation to internal ground floors or bridging the damp proof course.  Where a building has suspended timber floors and there is a ventilated void underneath, we sometimes find that this has had the ventilation blocked off as such that there is no airflow.

All of these scenarios can give rise to moisture being contained within the base of the wall and not being able to escape.  In such situations there is a possibility that the dampness will eventually rise, or appear to rise, up the wall. This is simply because the moisture has become trapped and cannot escape.  

In such situations the remedies are usually fairly obvious.  Removing impermeable finishes to allow the wall to release the moisture can often go a long way to resolving a damp problem.  Opening up vents to ventilate voids can also assist drying out sub-floor areas. Most importantly, lowering ground levels against the building can assist because then there is no longer the problem of moisture penetrating laterally through the wall.  I often find that by dealing with such matters the problem of dampness can be resolved without the need for specialist treatments.

The real source of dampness may not always be obvious

It must also be remembered that there may be other reasons why the base of the wall has become damp.  Some years ago friends of mine were trying to sell their house. They were both building surveyors and both involved with historic buildings and therefore understood these issues.  Their purchasers mortgage valuer undertook the usual tests and found an area of damp and declared that there needed to be a specialist report undertaken. That report concluded that there was a rising damp problem and the wall needed to be treated.  My friends refused to accept this because there was no internal visible evidence of a problem and they suspected that such treatment could cause problems. They quickly discovered why this area of wall gave a high reading – there had been a leaking gutter joint for some time that they had not realised was causing such a problem.  The water from this had gradually dripped onto the ground and splashed into the base of the wall. This created a localised problem of dampness in the wall. Internally it meant that a moisture meter gave a reading to a certain area and this caused the specialist company to decide that the appropriate remedy was chemical treatment.  In fact all that was needed was repair of the gutter and allowing the wall to dry out. This they did and then successfully sold the property without the need for any treatment.

Damp in modern buildings vs historic buildings

Modern buildings are constructed in a way whereby the design is intended to keep out moisture.  Modern buildings tend to incorporate physical barriers and have materials that prevent moisture getting into the building. This is all very good until that system fails and then when moisture enters it can often be quite difficult to find the point of entry and where one needs to repair.  In some situations, there may be a need for some form of specialist intervention, especially in buildings designed to keep moisture out.

However, for hundreds of years buildings were constructed and functioned differently. With older buildings (often taken to be those built before about the 1920s), the materials were permeable, and the buildings manage moisture rather than exclude it.  Therefore, a certain amount of moisture would be absorbed into the building fabric but this would then evaporate away again without causing any long-term problems. If we impose modern technology on older buildings, there is a chance that we create a barrier that was never intended to be present.  This can sometimes result in the moisture finding a way around the barrier or dispersing in areas where previously it might not have been present. In other words, inserting a barrier into an older building can sometimes force the moisture problem elsewhere rather than resolving it.

Of course, if it were possible to introduce a complete infallible barrier under every part of an old building this would resolve any problem of damp from the ground into the base of the building.  However, I have yet to come across any retrospectively inserted system that can be inserted under all parts and is indeed 100% infallible. Even if such were available the cost and disruption would probably be inhibitive for most buildings.

In reaching a conclusion to this article I recap as follows.  

  • Rising damp is perhaps the most misdiagnosed form of damp.  
  • When a damp problem is encountered one needs to consider the matter holistically.  No building was ever constructed with the intention that it remained damp and often one has to consider what has changed to understand what might have been causing the damp.  For example:

Has the ground level increased against the wall?  

Have sub-floor vents been blocked up?  

Has render or some other impermeable finish been applied externally or internally?  

Are there leaks in or about the area?

Of course, there are situations where the analysis of a damp problem will be more complex.  It may be necessary to employ techniques such as taking core samples from the wall to assess the dampness.  

There again there may be situations where the cause of the damp cannot be resolved.  For example, where there are high ground levels, but it may not be possible to lower the ground against the wall.  

A good building surveyor will be able to properly diagnose a damp problem looking at it holistically and taking all matters into account to devise a remedy that is appropriate for that specific building in those given circumstances.  

Modern technology provides us with new tools to assist in the diagnosis of damp – thermal imaging for example; a useful tool, but perhaps dangerous in the wrong hands!

I conclude by saying that rising damp may exist in some situations, but it is rare.  Often the cause of what seems to be rising damp can be found to be something that has happened to that building – what has been done to bring about a change to the building?  I am not saying that there will never be a need for specialist intervention but in my experience, it is extremely rare.

If you have what is thought to be rising damp, then seek advice from a competent independent surveyor who will take a holistic look at the problem and devise a bespoke remedy.  It is not free or cheap, but it is independent and provides a remedy specifically for your building and situation. At whitworth we can provide such a service; call us today on 01284 760421.

Towards the beginning of this piece I mentioned condensation, and this will be the subject of a separate article.

About the author

Surveyor Stephen Boniface joins BlueBox Partners

Stephen Boniface is a Chartered Surveyor at whitworth. Stephen has extensive experience in historic buildings and conservation work, and on a daily basis carries out a variety of work from surveys to expert witness.

In this post, Chartered Surveyor Stephen Boniface discusses structural movement and cracking, and covers the various reasons why cracks may appear in a building.

Cracks on a structure

A dilapidated structure made unsafe by cracking

Perhaps the most common concern that surveyors are asked to address when inspecting properties is whether there is structural movement to the building.  In recent years we have witnessed drier summers followed by drier winters and the incidents of movement seems to be on the up. However, there are many reasons why a crack might occur in a building.  In this brief article I cannot hope to cover all causes of cracking, but I attempt to provide an overview that readers may find helpful.

All buildings move

The reality is that all buildings will undergo movement of some description.  The issue is how that building copes with the movement. With most modern buildings they are designed to accommodate a degree of movement, particularly if large, unusual, or in an area where problems may occur regularly, e.g. earthquake zones.  

As this article is aimed at the residential homeowner based in the UK, we do not need to concern ourselves about some forms of movement.

Flexible -v- Inflexible

The materials we construct with will have a significant bearing on the likelihood of cracking occurring.  The crack is usually the first visible sign of any form of movement. Not all cracks are significant or such that need cause concern.

The main factor that determines whether a building cracks is the flexibility of the materials and of the structure generally.  

Some materials are quite brittle and will crack quite quickly under any stress or strain, whereas other materials can accommodate a greater degree of movement before cracking occurs.  For example, cement-based mortars and renders are more brittle than those that are formed using lime mortar. Therefore, we tend to find that modern materials and buildings often exhibit cracking far earlier than traditionally built properties when subjected to the same stresses and strains.  This sometimes results in quite significant distortion to an historic building with no cracks apparent whereas a modern building might have a number of cracks with no specific distortion apparent.

Therefore, an important issue to consider is the nature of the building and the materials from which it has been constructed.

Temperature & Drying Out

Broadly, temperature has an important part to play, but it is not only air temperature or the temperature of materials; it is also the moisture content in the air i.e. humidity.  

Some materials react to temperature changes with significant changes in dimension.  This means that materials might shrink or expand according to temperature and/or humidity.  When assessing cracking it is important to note when the cracking first appeared or was noted to have worsened because weather conditions generally might be a significant influence.

Oak cracking

An example of oak cracking

However, when thinking about temperature, the issue of heating within the building can also be a factor.  I have seen a number of historic buildings that started to move and cracks occur after central heating had been introduced.  The problem being that the materials in the building had reached an approximate equilibrium in terms of moisture etc, but the introduction of central heating dried out the interior of the building such that moisture was taken out of the materials causing them to dry out further.  Whilst this may not lead to any major structural problems it can cause some alarm for the occupant. It highlights the importance of careful consideration being given to the introduction of heating into a building that had previously been unheated, or where there is to be a major change in the nature of the heating.  

Drying out is a common problem, particularly for new build.  When buildings are constructed a significant amount of moisture goes into that construction.  My grandfather was a builder back in the mid-20th century and he used to tell me that they did not allow anyone to occupy a building for the first several months after it had been constructed because they wanted it to dry out and settle so that they could deal with any snagging, filling of cracks etc before anyone moved in.  Nowadays we tend to occupy buildings before the paint has even dried. It is no wonder that the occupiers then experience problems including cracks caused by drying out.

However, when repairs are undertaken to a building and a filler or areas of new plaster are used for repairs then some drying out should be anticipated.  Sometimes cracks can occur around a repair.

Different materials will have different rates at which they will dry out.  Also, materials will respond differently to temperature and moisture content. If different materials are placed alongside each other differential movement and cracking can occur.  

In recent years we have seen an increase in the number of people wanting to build extensions of oak and sometimes green oak is used.  This is oak that has not been subjected to extensive seasoning and has not been kiln dried. It will therefore still have some drying out to go through.  If the design of the building does not allow for such movement significant cracks can occur where the oak abuts plaster or other materials.

We also know that metal can have a significant response to temperature and where there are metal elements incorporated in a structure these might expand or contact at different rates to the surrounding masonry etc.  This then can lead to cracking at or close to the interface of the different materials.

Subsidence & Settlement

Sometimes one sees these two words used almost as if they mean the same thing.  

Settlement is where the building moves slightly when first constructed because the ground is taking the new weight above it and/or the structure is settling down partly due to drying out but also as the loads are distributed throughout the building.  Such initial settlement is not unusual. Of course, any distortions that may be related to this initial settlement will be with that building for the rest of its life and when looking at an older building one has to bear in mind that some of the distortions might have existed almost from the day it was constructed.  

Settlement can also occur when alterations are carried out to a building because loads within the building may have new load paths and the load may be distributed in a slightly different way.  Therefore, some settlement following significant alterations and extensions can occur. I quite often find that there has been slight differential settlement between parts of a building constructed at different times.

Differential crack

An example of a differential crack

On the other hand, subsidence is where the ground under the building moves.  This movement under the building leads to movement of the structure above.

Subsidence in many parts of the country is most frequently associated with shrinkable subsoils such as clay.  During dry periods the clay shrinks and the building above moves. Quite often the shrinkage of the soil is caused or at least exacerbated by trees and vegetation taking the moisture out of the soil.  Although you will regularly read of the common culprits such as willow trees, poplars and oak, I have seen examples of subsidence caused by privet hedges and even large rose bushes.

Subsidence can also occur if fine material in the soil is washed away or if the subsoil is easily eroded by underground water.  In such situations I have often found that leaking drains, gulleys etc have caused a problem. This usually leads to a localised area of subsidence to the building.  In some parts of the country subsidence may be caused by mining and other such activities under a building.

Where subsidence is suspected the cause of the ground movement needs to be established.  When I first became involved in dealing with subsidence issues in the 1980s it was quite common to underpin buildings but by the late 1980s and certainly into the 1990s it was realised that underpinning was not the panacea and in some instances caused more problems than it resolved.  

The approach now usually taken is to establish the most likely cause, deal with the cause and monitor the movement to see if the movement ceases.  It is only if removing the cause does not stop the movement, for whatever reason, that underpinning might need to be considered.

If subsidence is suspected monitoring the movement over a period of time is usually the first thing to be undertaken.  As part of the investigation it may also be necessary to look at the nature of the subsoils and perhaps take samples of the soils and anything found therein (such as roots) to see if this gives any indication as to the cause.

Subsidence can be quite worrying and is a lengthy process to resolve.  It can also lead to quite dramatic cracking. However, in many instances the problems can be resolved.

Other Ground Movements

Alongside subsidence one has to consider heave.  This is where the soil swells up and therefore lifts the building above it.  This is most commonly associated with clay where perhaps the clay has had trees growing in it or nearby that took out moisture each year.  If the trees are then removed the moisture stays in the ground rather than being removed and the clay expands. This can then result in heave.  

In the past, I was involved with a building where the structure itself had not undergone any movement, but the owners of this new house reported drainage smells.  To cut a long story short we found that the drainage under the building, within a void, had been crushed and moved by heave of the soil under the property. The area had previously been a woodland and whilst the foundations of the building had taken adequate account of this the void under the floor was inadequate.  Therefore, when the ground heaved it damaged all the drains. The solution was quite simple in that the soil had to be dug out to create a deeper void. As you may imagine the task was not the most pleasant for the contractors involved!

Landslip will not affect a property on a level site and rarely affects a property on a very gently sloping site.  However, where buildings are constructed onto or into a slope there is a risk of landslip. Landslip is often triggered by weather.  Perhaps a flash flood or excessive rain over a period may cause destabilisation of the ground and therefore slippage. Leaks to drains and pipes underground can wash away material and cause landslip. In some areas erosion along a coast can cause landslip.  

Whenever cracking occurs to a building built into a sloping site landslip should be considered as a possible cause.  

Chemicals

The construction of a building incorporates a large number of materials and therefore a number of various chemicals are introduced into the property.  Many of these are not problematic, but sometimes chemicals can result in movement.

For example, some chemicals will dissolve in moisture, but if the moisture evaporates the chemicals crystallise.  The act of crystallisation usually results in expansion because crystals take up a greater amount of space than the dissolved chemical (we often refer to them as salts).  Therefore, salt expansion can cause cracking.

In some situations, exposed elements of a building will be subject to weathering.  Weathering can react with chemicals within the mortar (usually by dissolving and then the salts crystallising) to cause expansion.  This can occur with chimneys, for example.

Overloading

I was once called in to advise on some cracking at first and second floor level within a Georgian terraced town house in London.  At first floor level was the principal reception room and the owners, who had recently moved in, had installed a bookcase along one wall.  I quickly realised that the load of the books had caused overloading to the floor and this had resulted in cracking above and around the area.  

In that particular instance we had an engineer design a method whereby the load of the bookcase could be transferred to the wall rather than being directly onto the floor.

In another instance I dealt with the refurbishment of a first floor flat in west London where the clients specifically kept a significant number of books.  Engineers had calculated that the load would be too great for the floor. Therefore, as part of the refurbishment the floor had to be strengthened and stiffened.

In the above examples books were the cause of overloading and in my experience, homeowners often underestimate the weight of books and paperwork.  When we find movement occurring or cracks around upper areas one has to think about whether there had been some overloading. This may apply to floors but can also apply to structures generally.  Another common cause of overloading is baths. Homeowners often underestimate the weight of a bath full of water and a body.

The load paths should also be considered.  We recently inspected a fairly modern building where there were significant cracks at first floor level.  It was noted that the ground floor room was one large open space whereas the first floor above had been subdivided into at least three areas.  The walls forming these subdivisions were of blockwork and in one area there was a boiler with hot water cylinder installed. Directly above this was a cold-water storage tank in the roof.  All of this load was directly onto the floor that was over a void with no partition or other support below. There had been significant overloading of the floor thus causing the movement.

Whenever there is distortion and cracking the paths of loads through the building should be followed and considered.

Deterioration

All buildings will eventually deteriorate with age.  How we maintain and look after them will determine how quickly or slowly they may deteriorate.  

Of course, if that deterioration results in rot or infestation to elements within the building these can result in movement.

Some years ago, I was asked to look at a problem of dampness within a Grade II* listed pub.  Upon inspection I realised there was active death watch beetle and clearly problems far worse than just dampness.  Some of the cracking at first floor level appeared recent.

I asked the contactors to carefully remove the cement render from the timber frame so that we could investigate.  When I returned the next day, the builders had only removed a very small part. Upon enquiring why, they informed me that the building had moved.  It turned out that the render was the structural element of the wall because the frame behind had deteriorated to such an extent that it was no longer able to support the loads above it.  

This was an extreme example of where rot and infestation resulted in movement, but of course failure to maintain a building is likely to result in various problems and one result of this could be movement if rot and/or infestation cause deterioration to timbers.  

Alterations

Over the years I have come across many Georgian and Victorian buildings with internal timber partitioning where alterations had created problems.  The belief of some homeowners was that because the internal partitions were timber, they could not be load bearing. This was in fact wrong because with many of these buildings the whole of the interior is timber construction and much of it does provide load bearing support for the floors and roof above.  In some instances, principal areas of bracing within the framing had been removed and movement had occurred above. Such matters are simply where the alterations were ill considered and poorly executed with inadequate allowance for re-distributing load paths.

A few years back, I was asked to investigate a problem of bulging to a wall that had been identified by a mortgage valuer as a serious problem.  The building dated back to the late mediaeval period and had started life as a mediaeval hall house with no chimney or upper floor. Within a few minutes of entering the property I had realised what had happened.  When the chimney and upper floor had been inserted some years after the house had been built, some of the principal members of the original hall house frame had been cut away. This resulted in lateral movement and hence the bulging.  Nonetheless, it is quite likely that the builders undertaking the work at the time realised their mistake very quickly because where the floor had been inserted it followed the bulge precisely and in fact the floor was now providing the required lateral restraint for the building.  

In that instance I was able to determine that the movements had occurred several hundred years before and was not an ongoing problem.

It does however highlight the fact that alterations can have a significant impact on a building and any changes need to be very carefully considered.  Where cracking and movement occurs to a building that has been altered one needs to consider what took place and whether that might be the cause of the present problems.  

Understanding

The key to identifying causes of cracking is to understand the nature of the building, its materials, construction, the site it sits on and what alterations might have been undertaken in the past.  It is only when all this information is available and can be properly considered that the cause of cracking can be determined.

Cracking can be quite an emotive problem.  Where clients notice a crack, they can become fixated on it; I have had some contact me on a regular basis to tell me the crack is worsening.  Upon investigation it is not, it is simply that they have become so focused on the crack that they perceive a problem when there is not one. Of course, sometimes, there is a problem and that is where the understanding of the building, monitoring the situation and proper assessment comes into play.

If you have a problem with cracking or are concerned about movement to a building, we here at Whitworth are able to provide advice. Call us today on 01284 760421 or visit our contact page here.

About the author

Surveyor Stephen Boniface joins BlueBox Partners

Stephen Boniface is a Chartered Surveyor at whitworth. Stephen has extensive experience in historic buildings and conservation work, and on a daily basis carries out a variety of work from surveys to expert witness.

In the following article, Chartered Surveyor Stephen Boniface tackles the subject of condensation, including the issue of condensation mould, how condensation can be confused with rising damp, and what to do if you find these problems in your home.

Condensation mould on walls near ceiling

An example of condensation mould

In a previous article I discussed the myth of rising damp. I mentioned that whilst damp may occur very low in a wall it rarely, if at all, rises up the wall.  Nonetheless, what appears to be ‘rising’ damp is usually another form of damp. I mentioned that rising damp was the most commonly misdiagnosed form of damp and yet the most common form is in fact condensation. In fact, damp identified as rising damp is often condensation. This article considers the issue of condensation and what a homeowner might be able to do to combat it.  

Condensation can be complex

A proper consideration of condensation involves looking at temperature (of air and internal surfaces), absolute and relative humidity, thus leading to an assessment of dew point and an assessment of the likelihood of condensation occurring either on surfaces or within a structure.  This can be quite complex, involving various pieces of equipment (e.g. temperature and humidity sensors, thermal imaging, etc.), as well as assessment and calculations that often have to be undertaken over time to gain a proper understanding of what moisture is doing in a building. The time of year will also affect the appearance of condensation damp and its assessment.

Nonetheless, this article is aimed at a homeowner and how a homeowner might be able to combat condensation.  

Put quite simply warm air can absorb and hold water as a vapour whereas cold air cannot.  If warm moist air meets a cold surface then it is forced to release that vapour as liquid (water), hence condensation.  To compound problems if that moisture stays on a surface for any length of time the risk of mould occurring will increase.  

Lifestyle is often a problem

The one key factor when considering condensation is the occupiers of the house.  Most condensation problems can be traced back to what the occupier does or does not do, i.e. lifestyle. Our very presence will create moisture and daily life operations such as bathing, cooking, etc., will elevate moisture levels. If you have a habit of drying clothes inside this will simply add to the moisture in the property.

When considering condensation, the three issues that are usually considered are:

  • temperature, of both the air and internal surfaces;
  • ventilation, how moist air escapes the building and/or the air changes within a building;
  • insulation, of surfaces and/or spaces within a building.  

The most common problem is where an occupier creates warm moist air that does not escape from the property quick enough thus leading to condensation and mould problems.  I have three daughters and when they lived at home a common problem was that they believed the bathroom was not a suitable environment to step into unless it was like a sauna.  They would run the shower hot for a period of time before stepping into the bathroom. Upon completion they would leave the window closed (because they did not want to introduce cold air) but leave the bathroom door open while they got dressed.  It was not long before the moisture in the air met the cold external wall and window surfaces and became condensation. The other problem with this is that leaving the bathroom door open meant that some of that warm moist air escapes into other parts of the building where it might then cause further condensation problems.  

The above scenario is probably quite common in many houses up and down the country.  The solution is quite simple. When finished in the bathroom the window should be opened and the door should be closed.  This will mean that the warm moist air should escape out through the window. Of course, if you have an extractor fan fitted then this should be turned on to aid the evacuation of the warm moist air.  In fact, all bathrooms, showers and kitchens should be fitted with extractors (suitably positioned) so that moist air is removed speedily.

In kitchens cooking can lead to excessive moisture in the atmosphere.  I was once asked to investigate a problem of damp in a flat contained within a block of flats.  As the door of the flat was opened the problem was immediately apparent. Before I had even stepped fully into the property the tropical atmosphere within caused my glasses to steam up.  Upon entering I noted that the occupant had a couple of pans of water on the boil on the stove as he was in the process of cooking his daily meal. None of the windows were open and there was no extractor in use.  It was no surprise that when this warm moist air met the external walls and windows of the flat that it became condensation. Because the occupant had not wiped that moisture clear it had become mould and there was a serious problem of mould to exterior walls and windows.  Although the construction of the property did not help matters, the lifestyle of the occupant was clearly a major contributory factor if not the cause of the problem.

In another situation I was asked to investigate a house that had recently had double glazed windows installed.  They had a problem of condensation moisture that had not previously existed. I advised them that there although they could insulate walls, etc., this would be expensive and disruptive with no guarantee that the problem would be resolved.  However, I noted that the bathroom and kitchen already had extractor fans and recommended that they use these on a regular basis. I find that most extractors have isolation switches and in the vast majority of houses these remain turned off most of the time. This is often because of the noise of the fan! In the case of this house I noted that they had all the windows closed (and locked – for security). My advice, which went down badly, was that they should open the windows on a regular basis to allow the warm moist air to escape.  Upon being told this they exclaimed that they did not want “to lose the heat from the windows now that they had spent a lot of money on having double glazing installed”.

A serious problem we face today is that many homes are being insulated and sealed to a degree that has not been known or indeed possible previously. This means that the air changes within a property are reduced and as a result warm moist air does not escape so quickly and the risk of a condensation problem increases significantly.

An example of air change problems came about some years ago when I was asked to investigate a problem of a damp smell in a ground floor flat within a converted Victorian building.  The owners had recently had double glazing installed and they were a young couple who were both out at work all day. The problem was that when the owners returned home each evening the smell in the property was quite overpowering.  I quickly realised that their lifestyle meant that in the morning they showered, had breakfast and prepared their meals for the day and then both left closing the door behind them. They left the property for perhaps eight to ten hours and when they returned home, having had double glazing installed, they were met by the same stale air that they had left.  There were simply insufficient air changes in the day to change the atmosphere. In that particular instance the introduction of extractor fans to the kitchen and bathroom and advice to open windows as soon as they returned home did resolve the problem for them.

Heating

Earlier I mentioned the three factors that can influence matters.  

The first of these is heating. It is important to ensure that a property has a reliable heating system of some description.  The dew point is the point at which the temperature of air changes such that the air can no longer hold moisture as a vapour and has to release it.  The actual temperature will vary depending on a number of factors. However, if temperatures within a property fluctuate considerably throughout any given day or over a period then the risk of hitting the dew point increases.  If the temperature is more constant and kept above the dew point, then the risk of condensation is generally removed. Therefore, retaining a fairly constant temperature in a property is perhaps the best way to avoid condensation. However, as the air temperature rises it can hold more moisture and the risk of condensation increases. As a general rule keep heating on, but low, at all times and generally it is thought that a sensible temperature range should be around 10-20°C.

Of course, this refers to air temperature and I earlier mentioned that surface temperature can have an important part to play in some buildings. This is certainly the case with some materials or elements within a building. If the temperature of some surfaces is particularly cold, then a risk of condensation remains.  In some buildings it may be straightforward to provide insulation, but it is not always easy, is often expensive and therefore not an option. The issue of raising surface temperature to walls and other parts of the structure can be quite complex and for this it is best to seek professional advice. Inappropriate insulation could create rather than resolve a problem.

Windows in older buildings are single glazed and these might be a cold spot and therefore prone to condensation.  Double glazing is an option for many buildings, and it can indeed increase the temperature of glass but does not completely preclude the risk of condensation because glass itself is a relatively cold material.  With listed and older buildings, the installation of double glazing may not be an appropriate option and may not be permitted. As an alternative secondary glazing can provide an improvement in terms of reducing heat loss.  In many ways secondary glazing can be more efficient that double glazing because the whole of the window opening is covered by a second layer of glass not just the panes themselves.

The one disadvantage of double or secondary glazing is that draughts are reduced, thus reducing the number of air changes in the property.

That said, the benefit of secondary glazing is that it can be removed when it is not required, e.g. during summer months.  The main problem is that it is necessary to have other methods of ventilating the property and creating air changes.

When considering these matters, it must be borne in mind that wet surfaces are colder than dry surfaces.  Therefore, if a section of wall is wet (for any reason) then it would be colder and more prone to condensation to the surface.  

Ventilation

The next matter to consider is ventilation. This is perhaps the most important matter to consider when assessing condensation. I sometimes remind clients, who wish to keep their homes sealed up, that barns don’t suffer condensation because they are draughty open spaces with a lot of air circulation.

I have already discussed the use of extractor fans and opening windows.  These are fairly straightforward and relatively cheap methods by which a property can be ventilated.  It is important to use these to create air circulation and therefore air changes, which will help remove the warm moist air. Other simple things to consider include regular opening of cupboards (particularly wardrobes) to air inside and moving furniture away from walls.  The aim being to avoid areas where air can become trapped. As previously mentioned, avoid drying clothes inside wherever possible, don’t add to moisture levels unnecessarily.

With a modern building, designed to keep heat in and minimise heat loss, there is an inbuilt problem of a lack of air change.  Because of this a number of systems have been developed in recent years to ensure that the building has a constant supply of fresh air coming in and air changes generally.  Certainly, with modern buildings whole house heat and ventilation systems are increasingly common. These can work well but will need to be properly maintained.

Talking of maintenance, it follows that any item in the property that needs maintenance should be looked at regularly.  This will include the boiler and heating system as well as any extractors or other form of mechanical or electrical ventilation.

When considering extractor fans, I would point out that there are humidity-controlled extractors on the market.  In situations where an occupier might forget to turn on an extractor or where there is a high humidity on a regular basis it might be appropriate to install a humidity sensor that will automatically trigger the extractor fan.  There are also dehumidifiers available for domestic situations and these can be useful.

Insulation

I have already touched upon the issue of insulation.  Most homeowners are well aware of the need to insulate roofs.  It is becoming rare to find a property that does not have adequate or some level of roof insulation.  

The government have brought about schemes together with the energy companies whereby some home owners can benefit from having their roof spaces insulated for free.  Whilst this is of some benefit, I have noted a number of problems over the years where this scheme has been operated. The problems usually lie with the contractors installing the material.  Quite often I see that the insulation is unevenly laid with serious gaps in some areas. I often see it laid in such a way that the insulation is in direct contact with the underside of the roof tiles or lining and this can result in problems of condensation moisture dripping down.  The other problem is where a roof slope is lined there can often be insufficient ventilation in the roof space and condensation occurs in the area above the insulation.

When laying insulation care has to be taken with electrical services because you do not want these to be overheating.  If there are walkways to water tanks or other areas in the roof these often need to be raised to allow the insulation to be placed underneath.  

The one thing I have mentioned but not discussed is the surface insulation of walls.  One can insulate from the exterior or from the interior. External insulation is more efficient because it covers the whole house – assuming it bridges to roof insulation so that there are no gaps in the insulation over the property.  However, it can be expensive because it involves quite a lot of changes to the exterior. It creates a new wall surface that is beyond the face of the existing and therefore details such as windows and doors have to be changed as well as consideration given to matters such as the eaves of the roof.  The application of an external system is often far more involved than simply putting insulation on the wall face. Nonetheless, if it can be installed it is often efficient at reducing heat loss.

Internal insulation is perhaps slightly easier to install because it can be dealt with during redecoration.  However, internal insulation also changes the thickness of the wall and means that internal skirtings, windows and doors, etc might have to be altered.  The other problem with internal insulation is that there will be a number of voids that are often forgotten and not insulated. Here I refer specifically to floor voids between the ground and first floor and these will form cold spots within the insulation.  

If you are considering wall insulation the matter needs to be assessed properly so that the system once installed is beneficial and does not create problems. The other thing that needs very careful consideration is the type of insulating products.  If they are impermeable, they could result in trapped moisture, as already mentioned. However, there are a range of permeable products that can be used and should not create a problem of trapped moisture.

There are materials within a structure that can act as cold spots; examples include concrete lintels over window and door openings.  Sometimes condensation is found to occur to such areas but not elsewhere. It may be necessary to consider insulation of certain areas to reduce the cold spots. Again, this is something that needs to be carefully considered if such a problem exists.  

Another scheme that has come about in recent years (from the government and energy companies) is the insulation of cavity walls.  This could be the subject of a separate article but for now it is important to note that filling a cavity wall with anything means that it is no longer a cavity wall but a solid wall.  The risk of moisture transferring from the outside to the inside increases but this will depend on the nature of the cavity insulation and how the work is undertaken. Another issue is that some materials used to fill cavities will lose their insulation values when wet whereas others do not.  It has been found that in some locations in the country cavity insulation has created a problem of condensation. In those situations, the cavity insulation has had to be removed. Indeed, there are several companies that started off insulating cavities but have become specialists at removing cavity insulation because of such problems.  Therefore, cavity insulation needs to be very carefully considered by a specialist who understands the issues and can specify the most appropriate product and method, or even be prepared to advise against it.

Although the issue of cavity wall insulation is one that is often pushed as a good thing, in my experience it is best avoided. Whilst there may be some advantage in terms of improved thermal retention it can be outweighed by the problems of damp it can cause.

The other major issue, as already mentioned, is that many insulation products are not ‘breathable’ and can result in trapped moisture. Before any insulation is applied to surfaces or cavities a holistic assessment should be undertaken.

Maintenance

It should be remembered that wet walls are cold and therefore more prone to condensation. As discussed above, the materials used can affect whether a wall remains dry or is wet.  However, it follows that maintenance of a property is paramount, to ensure that dampness does not become a problem.

Most damp problems originate from a failure to maintain, or perhaps react to a defect with sufficient speed.  

In this country perhaps the most important consideration for any building is keeping rainwater out.  Regular checking of the exterior and dealing with timely repair, etc., will go a long way to prevent water problems internally that often then lead to condensation.

Condensation mould near skirting boards

Another example of condensation mould on walls

Mould

I have not so far discussed mould.  Quite simply if condensation moisture is allowed to remain on a surface mould is likely to occur.  

I am not a medical expert, but over the years I have learned that mould is not usually the primary cause of respiratory problems, but will exacerbate an existing respiratory problem, sometimes revealing a respiratory problem that the person did not realise they suffered. During a holiday to a humid location one of our daughters suffered breathing difficulties that were not experienced before and have not been suffered since.  Humidity and mould that might result from condensation can have an impact on health that might be temporary but could be permanent.

Mould in any property is not good.  If mould occurs, then it should be carefully removed with suitable detergents – there are many on the market designed to remove mould.  Some paint and other finishes are designed to reduce the risk of mould occurring and might be useful in certain situations.

However, the best way of reducing the risk of mould becoming an issue is to ensure it cannot occur in the first place.  Therefore, good ventilation will help air circulation, avoid high humidity and if condensation occurs remove the moisture quickly to stop the risk of mould growth.  In situations where moisture occurs regularly the homeowner should make every attempt to remove it quickly. To some surfaces, this will be easier than others – at its simplest it might mean having an old towel to hand whereby the surfaces can be periodically wiped down.

Rising Damp or Condensation?

The fact that what appears to be a damp problem is most commonly found at the base of a wall is no surprise. One must remember that because of gravity all forms of moisture will eventually work their way down a wall and could accumulate there. Because of this one must consider that just because the appearance of damp is at the base of a wall the damp may not be ‘rising’ at all.

In a previous article I argued that the base of a wall is most likely to have some damp in it; which may be absorbed from the ground, penetrate from the ground, made it’s way in from the exterior (rain, ground water, leaks from above, etc.,), etc. A wall that has moisture in it (for any reason) is going to be colder than a dry wall. As cold air falls anyway, the likelihood is that the coldest part of any wall will be at the base. In this article I have pointed out that if warm air meets a cold surface it will release the moisture when it reaches dew point. As the base of a wall is most likely to be colder than upper areas it follows that the base of a wall is a zone where condensation is likely to form. In my view damp at the base of a wall is more likely to be condensation and/or other forms of damp, but very rarely is it rising damp. Condensation must be considered as one of the most likely causes where damp appears at the base of a wall.

Summary

In summary:

  • Condensation is now the most common form of damp and is often misdiagnosed.
  • Heating should be constant to avoid highs and lows.
  • Insulation can prevent heat loss (important from an overall environmental viewpoint) but has to be very carefully considered and properly installed.
  • Avoid materials that are impermeable and likely to lead to trapped moisture.
  • Ventilation is vital because all properties need regular air changes.
  • Moist air created within a property should be removed quickly and this usually involves extractor fans at the main sources, i.e. kitchens and bathrooms. However, nothing beats the simple act of opening windows.
  • Maintain the property to avoid leaks and water ingress.

This article cannot hope to deal with every aspect of condensation, dampness and the mould that can follow but hopefully give some guide as to the main issues and matters that a homeowner could consider if they find themselves with a condensation problem.  Of course, if the problem is not one you are able to resolve you might need professional advice and here at Whitworth we are able to assist you in this regard.

About the author

Surveyor Stephen Boniface joins BlueBox Partners

Stephen Boniface is a Chartered Surveyor at whitworth. Stephen has extensive experience in historic buildings and conservation work, and on a daily basis carries out a variety of work from surveys to expert witness.

Chartered surveyor Stephen Boniface clears up the mystery around rot, including what it is, how it works and what you should do if it is discovered by a building surveyor.

In recent articles I have considered the problems of damp and in this article, I turn to consider the allied issues of timber rot and infestation.  

Rot on jetty

Rot on a jetty

The Fear of Rot

Perhaps the one thing that causes most fear to a client is when a surveyor declares that the property has a ‘dry rot’ outbreak.  Over the years I have had clients who have been under the impression that if they have dry rot in a corner of the building today then within a short period of time the whole building will have collapsed due to the rot spreading and causing destruction throughout.  This is, of course, completely wrong and in this article, I will attempt to explain why and what can be done when problems do arise.

What is Rot?

We commonly refer to dry rot or wet rot, both being misnomers that are misleading. Each are fungal growths that have adapted to live off wood and therefore take their nutrients from wood.  In so doing they each live off and destroy specific (different for each) parts of the wood, thus causing it to lose its strength and general integrity.

When thinking of a fungal growth it is often useful to think of the mushroom.  This requires very specific conditions to grow and in the right conditions it will flourish.  When the conditions are not appropriate it will not grow at all.

Better descriptions of these rots are brown and white rot.  Dry rot is a member of the brown rot family whereas wet rot is a member of the white rot family.  Because each of these attack different parts of timber they have different characteristics. Nonetheless, they are both a form of fungal attack and have some similarities.  Particularly, they require timber as a source of nutrient and there has to be a source of moisture; without both the spores will not germinate. However, they also benefit from other conditions including humidity level and amount of light.  

How Rot Functions

It is not the purpose of this article to provide a scientific treatise on the subject but to help homeowners understand the problems and allay some fears they might have.

With regard to the source of nutrients we are surrounded by timber in some form or another.  These fungal growths perform a very useful task in woodland and forests because they help to break down timber, particularly on the forest floor where the timber has fallen and become damp.  Without the help of such rots and infestations breaking down the timber our woods and forests would be full of fallen trees. However, the one place we do not want these rots to flourish is in our homes.  

It is often said that if we sample the air about us, we would find spores from these rots because they are all around us in the atmosphere.  If this is so and if wood is so abundant the question has to arise: why do we not see much more rot?

The answer is simply because the spores are not easy to germinate.  They require a high level of moisture (despite the term ‘dry’ rot) in addition to a source of timber.  A piece of timber that is dry, occasionally gets wet and then quickly dries out again, a piece that has a low level of moisture, or even a piece of timber submerged in water, will not have the right level of moisture or the right conditions for the spores to germinate.

I have heard it said that dry rot can transport its own moisture to ‘wet up’ dry timber, but this is simply not true.

As the rot germinates and starts to grow it sends out its mycelium (or roots) in search of nutrients.  Whilst these will have an amount of moisture in them, they do not transport dampness to ‘wet up’ dry timber.  Rather, if the mycelium encounters timber that is wet they can develop (take root) and take nutrients from that timber thus causing the outbreak of rot to spread.

Rot Myths

If it were true that dry rot could transport its own moisture to cause timber to become sufficiently damp, we would see far more rot around us and have a far more extensive problem than exists.  

Some years ago, I was asked to inspect a mediaeval house that was timber framed but had sadly been left unoccupied for approximately thirty to forty years.  Over those years a roof valley had leaked quite seriously in one corner of the building; there was a very serious and extensive outbreak of ‘dry’ rot to that corner. As I neared the outbreak, I wondered how close I would be able to get before I might fall through the floor! In the circumstances (a very dilapidated building) one would have expected that this rot would have more or less destroyed the building over a period of thirty to forty years.  In fact, I was able to get to within 1m of the outbreak before the floor started to deflect. The rot was not found elsewhere despite the extensive amount of timber.

The conditions in this property were apparently ideal for the rot to cause widespread damage but why had they not done so?  The simple reason was that the rest of the building was dry, and the rot had occurred and flourished only in the area that had become damp.  The rot was unable to transport its own moisture and only caused localised damage to the area where the timber had become damp; in this case because of a leak.

Some years ago, I attended lectures by Brian Ridout who had undertaken much research into rots and infestations.  A matter raised at the time was that of chemical treatment for rot outbreaks. What was explained at that time is that many of the chemical treatments we use to try to combat rot have an active chemical that is intended to kill the rot, but it is transported by water.  Therefore, when we spray the chemical onto a piece of timber we are introducing further water to that situation. Rather than kill the rot some chemical treatments might help it. Indeed, I recall seeing a photograph of a trial whereby Brian had been able to germinate rot spores in the chemical intended to kill the rot. What Brian explained that day explained what I had witnessed prior to then and many times since; that rot had returned to treated timber where the damp problem had not been adequately resolved.

Brown rot

Brown rot

What to do with Rot

So, what should we do if we encounter an outbreak of rot?

The first thing to remember is that a rot outbreak means there must be a source of moisture.  In fact, it is not just a small amount of moisture but significant levels. This might mean a sudden amount of moisture being introduced such as a flood or when a fire is put out, but it might be a small leak that has accumulated to become a lot of moisture over a period of time.  Therefore, the most important action is to find the source of moisture and deal with it. No amount of chemical treatment will deal with the rot if there is still a source of moisture; the rot might be temporarily halted but will return.

That said, there may be an appropriate time for some treatment.  In a situation where the source of moisture has been eliminated and the building fabric is being dried out (but taking some time), there may be a situation where a piece of timber needs temporary protection during that drying out process.  It might be appropriate to undertake some carefully targeted treatment to provide the additional protection that timber might need for a limited period. However, this must be very carefully considered bearing in mind that the treatment could introduce water to the timber.  Often, rather than such treatment it is better to monitor the levels of moisture over time to ensure the timbers are drying.

Because moisture is the key to the problem of rot, where there are timbers that might be vulnerable it is sometimes necessary to monitor a situation.  This might mean taking regular readings of the moisture content of the timber to establish whether the levels are at a point where the timber might be vulnerable.  In some situations, you might need to think about installing a data logger. This is a system whereby a sensor or reading equipment is installed in a permanent or semi-permanent situation and the readings can be taken remotely to plot the moisture content over a period.  This information can be gathered over time. From this a suitable method of treatment or repair can be devised, or it may be that a decision is made for monitoring to be continued and intervention only undertaken if the moisture levels increase to a point whereby they might cause an outbreak of rot.  

In some situations, I have seen brick and stone walls irrigated with chemical treatment in the hope that this would prevent a rot outbreak.  As already mentioned, because the chemicals themselves are usually water based such irrigation can often increase the level of damp in a wall and increase the risk of rot.

I have heard it said that rot will grow through and feed off masonry.  Again, this is untrue. Whilst the mycelia will grow and try to find a source of nutrient and water these could grow through cracks and gaps in masonry.  However, they do not cause the masonry itself damage.

Another problem I have come across in the past is a belief that where there has been a rot outbreak the timbers need to be cut back at least 1m beyond the last sign of the outbreak.  This often results in unnecessary and extensive work. Of course, if rot has caused a piece of timber to lose its structural integrity then that timber needs to be removed and a new piece installed.  In so doing it is necessary to check the timber to ensure that any rotten timber is properly removed and replaced. However, it is not necessary to remove dry timber that has not yet been affected by rot.  

In some situations, timber will have to be installed in a wall or positioned within a property whereby it might become damp in the future.  It is sometimes appropriate to install an isolating membrane around the sections of timber that are likely to be in contact with a wet surface.  This will mean there will be some separation between the damp material and the timber itself. This should help prevent the timber from rotting. However, part of the process should also ensure that the timbers are as well ventilated as possible because air circulation around the timber should help to remove moisture and reduce the risk of problems arising.  

When dealing with a rot outbreak it is important to identify the specific nature of the rot because this helps to understand precisely what damage it might be causing.  However, the basic treatment is much the same regardless of the nature of the rot. The source of moisture must be identified and removed or at least reduced (if the source of moisture cannot be eliminated).  The vulnerable timbers should be adequately protected and where timber has already been degraded it will need to be removed and replaced. Whilst chemical treatment might be appropriate as a temporary protective measure in certain specific circumstances chemical treatment itself is not an appropriate remedial measure for rot outbreaks.  Monitoring moisture levels in vulnerable timbers might be appropriate. Anyone with a rot outbreak should be extremely wary of any contractor wishing to treat with chemical but not deal with the other issues of moisture etc. as outlined above.

How trees work

When considering timber and the fact that the piece of wood in your property started life as a tree it is useful to remember that when growing as a tree it transported moisture up its trunk from bottom to top.  When we convert a tree into timber for use in buildings, we can see the grain. This grain is the natural route for moisture up a tree and the end grain that will more readily absorb moisture than the side of a piece of timber, i.e. across the grain.  Therefore, wherever end grain is exposed to moisture it is more vulnerable to absorbing moisture and then for rot or infestation to occur.

The importance of maintenance

Most rots prefer darkness and do not usually thrive in light.  This causes us a problem because it means that rot is more likely to be in the hidden areas of a building.  The first we know of a rot outbreak may be when a timber begins to fail. Often the rot will cause a lot of damage behind the surface before it becomes visible on the surface.

If we maintain our properties in good condition this will reduce the risk of water ingress and therefore the risk of dampness getting into hidden areas and causing concealed problems.  

The number of times we have had to deal with serious outbreaks of rot costing thousands of pounds to remedy and repair when the simple act of clearing a gutter or roof valley would have prevented water ingress and therefore the outbreak of rot.  Maintenance of a property is often the key to preventing such problems from arising.

Death watch beetle infestation

Death watch beetle infestation

Beetle Infestation

Associated with rot and dampness are beetle infestations.  There are a number of beetles in the UK that can destroy timber but the two most frequently mentioned are common furniture beetle and death watch beetle.  As with rot, in the right conditions these can cause a lot of damage but otherwise cause little harm.

In both instances the beetles themselves are small and their jaws are smaller still.  Quite simply they do not have the strength in their jaws to eat through well-seasoned dry timber.  Therefore, for a beetle infestation to flourish there needs to be a certain moisture level in the timber and the timber fibres need to be breaking down to be soft enough for the beetles to consume.

Common Furniture Beetle

Common furniture beetle has a life cycle of approx. three years or thereabouts.  The adult beetle will lay eggs and the larvae burrow into the timber for a few years before exiting and becoming adults.  The cycle then repeats. They primarily attack soft woods but can attack the sapwood of most timber if it is soft enough, i.e. through damp and rot.  It usually eats its way out of the timber and its emergence creates what we commonly call a flight hole. Over time a heavy infestation can weaken timber and cause it to fail.  

If there is an outbreak of common furniture beetle it is an indication that there is dampness around.  This could be atmospheric damp such as condensation but there might be other forms of dampness and this needs to be addressed.  Properties (or areas within) that have high levels of humidity are vulnerable to infestation because the timbers generally have elevated moisture levels.  Control of humidity and dealing with condensation will go a long way to help reduce the risk of infestation.

Many timbers will suffer from infestation in their early years (whilst they are still drying out) and before they become fully seasoned.  With modern properties many structural timbers are pressure-treated to provide some protection whilst they season and dry out. In older properties the timbers are already seasoned and infestation occurs usually only if timbers become damp.

If active common furniture beetle is identified targeted chemical treatment to surfaces can be effective.  Note the use of the word targeted because widespread treatment simply for the sake of it is unnecessary and a waste of money.

Death Watch Beetle

Death watch beetle has a lifecycle that can be around ten years or thereabouts.  Like common furniture beetle the adults lay eggs that form larvae, which then eat through the timber to eventually emerge and become adults to repeat the cycle.  Death watch beetle tend to attack hard woods and is not usually found in soft wood. Even so, it generally only attacks the sapwood and is rarely found in the heartwood unless the heartwood itself is deteriorating through damp and rot.

Death watch beetle does not always create its own flight holes but can sometimes enter and emerge through cracks and gaps in the timber.  Because of this, and its long-life cycle, surface treatment is rarely effective and is not something I would recommend.

With death watch beetle it is far more important to identify precisely where the outbreak exists to undertake specific targeted treatment and repair.  The problem here is finding out precisely where they are. In some instances, the damage that might be caused in finding the outbreak could be greater than the outbreak itself is causing.  If the outbreak is limited to a couple of mating pairs then it may not be appropriate to undertake any work at all but to monitor the situation.

How to tackle beetle infestation

Where there is a significant outbreak it is first and foremost an indication that there is damp rotting timber.  As with the issue of rot it becomes necessary to deal with the dampness as the primary method of remedying the problem.  Dealing with the damp will often then expose the infestation allowing it to be removed, and, if necessary, very specific targeted treatment undertaken. Of course the damaged timber will need repair and/or replacement.

With historic timber framed buildings, where the frame is covered in part or fully by render, plaster etc., the first sign that there is a concealed damp and perhaps rot problem is usually the emergence of death watch beetle. In such situations it is essential that advice be obtained from someone who can consider the problem holistically and advise on a bespoke solution appropriate for that property and that situation.  Although chemical treatment might be part of that solution it will not be sufficient without dealing with the dampness and rot.

Identification of activity

Identification of activity is of course important.  I have already mentioned flight holes and for common furniture beetle these are usually approximately 1mm in diameter but for death watch beetle they can be up to approx. 3mm in diameter.  When looking at or into the hole if you see a dark dirty interior it will be an indication that the hole is old. However, if the edges of the hole are crisp and just inside the hole appears to be clean fresh timber it could be an indication that the hole has recently been formed and that there is activity.  If you suspect activity a quite simple solution to help identification is to use flour paste and paste a piece of tissue paper over the suspect area. If there is activity the beetles will emerge through the tissue paper and holes will be seen in it.

These beetles are generally active in the spring to early summer period and this is when you need to look out for evidence of activity.

Summary

The most important thing to remember is that dry timber will not suffer from rot or infestation.  

The key to understanding and dealing with these problems is an understanding of dampness, how this can affect timber and how to deal with the damp.  

 

In this article I have discussed in general terms the issues of rot and infestations.  If you suspect any such problems in your property you need to seek specialist advice from those experienced in dealing with such issues but also from those who are able to take a holistic approach and are not wholly reliant on chemical solutions as a remedy.  Here at whitworth we are able to provide independent advice on rot and infestation issues.

About the author

Surveyor Stephen Boniface joins BlueBox Partners

Stephen Boniface is a Chartered Surveyor at whitworth. Stephen has extensive experience in historic buildings and conservation work, and on a daily basis carries out a variety of work from surveys to expert witness.

Last week, our building surveyors were involved with several interesting projects involving listed buildings.

Listed building surveys

Listed Building Survey in Greenwich, London

A Grade II* property surveyed by Whitworth

We were asked to provide ongoing services for the interior refurbishment of a Grade II* property that we had surveyed last year. A Grade II* listing defines a building as particularly important with more than special interest. Whitworth has worked on a range of Grade II* listed buildings, such as a property on Angel Hill in Bury St Edmunds and a historic timber framed building with a Scheduled Ancient Monument moat.

 

Angel Hill, Bury St Edmunds

Angel Hill, Bury St Edmunds

Heritage Statement consultancy

A second property involved the preparation of a Heritage Statement in connection with repairs and some replacement of windows. A Heritage Statement is usually required by local authorities alongside proposals affecting a heritage building. The statement contains an analysis of the significance of heritage assets, and the potential impact of the proposed development upon its historic value.

 

Whitworth surveying project

A heritage Statement was prepared for this dwelling by Whitworth surveyors

Pre-purchase inspection

The third property was a pre-purchase inspection, providing advice to the client on what they need to consider when purchasing a property of this type and age. Pre-purchase inspections will reveal elements of a building that may not be obvious to potential buyers, such as structural damage, asbestos and rising damp.

 

Historic building surveyed by Whitworth

We carried out a pre-purchase inspection on this property

If you are thinking about purchasing, renovating or converting a listed building, contact our surveying team on 01284 760421, or visit our contact page.