Subsidence – Part 2 – Factors that contribute to subsidence

As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection. It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important

Source: Confused.com

In my last article I gave an example of the consequences of building subsidence, which can be extremely disruptive and expensive to deal with, however I also emphasised that the vast majority of subsidence damage is less serious and can be rectified reasonably easily. I also explained that to the average householder the mere mention of the word subsidence strikes fear and panic into them as there is a perception that subsidence damage is always serious. As you would expect and as I have mentioned many times before, if you are thinking of purchasing a property it is always advisable to have a professional, such as a Building Surveyor, inspect the building before you commit to buy. The Surveyor’s report will identify any issues that are present and inform you if any are serious. A Building Surveyor will also highlight factors that may contribute to subsidence in the future and not just focus on the here and now. There are a number of factors that could lead to subsidence and some examples are discussed below:

Clay Soils - To support a building it is essential that the load bearing capacity of the ground is capable of supporting the dead load of the building (the building’s self weight) as well as any imposed load (furniture, fitting, people, snow etc.), once completed and occupied. The type of ground is essential to a building’s stability as this will determine the most appropriate as well as the depth of the foundation that should be used. When siting a building, clay soils are particularly problematic compared to most other types of soil because clay has the ability for significant volumetric change depending on how much water/moisture it contains at any particular time. When clay is wet it will swell and therefore expand, however when the ground starts to dry out all of this moisture is slowly removed and the clay will shrink. Think about this process happening with a building on it!  If the ground is constantly expanding and then shrinking, then it is inevitable that the weight of a building will eventually be affected by these changes and cause the building to move. Having said the above there is no reason why a building cannot be constructed on clay as long as this is established through ground investigations and appropriately catered for in the design. This may involve deeper foundations, as well as the inclusion of root barriers where trees and vegetation may be in close proximity to the building.

Trees - Whilst inspecting a property, as well as focussing on the building itself I would always look very closely at the surrounding environment and in particular the size and location of trees. If not managed trees, and in particularly their roots have the ability to undermine foundations, damage drains and cause significant damage to a building. The problem with tree roots is that you often cannot see the extent of the root growth or proximity to the building because they are buried. This however does not mean that they should be ignored and where trees are deemed the pose a threat to a building then the services of a tree expert (Arboriculturist), should be called upon. This is necessary because different species of tree will exhibit different characteristic in terms of size, growth rate, root spread etc in addition to the advice that can be provided in respect of the condition of trees and any recommended remedial action.

Source: Absolute Plumbing and Drain Cleaning Services

Tree roots do a number of things when in the ground. Firstly, they take up large amounts of water. Given what has been discussed above in respect of clay soils you can easily see that in continued spells of warm weather and high temperatures that clay soil and tree roots are not a good combination and together this will significantly increase the potential for subsidence. Secondly, as the roots grow they have the ability to physically impact on soils, particularly the soft/granular types which can undermine their stability especially when they have a foundation and a building siting upon them.  Also, tree roots have the ability to damage below ground drainage.

Drainage - Although it is possible to make a broad assessment of a drainage system during an inspection by lifting manhole/inspection chamber covers this is limited to a small number of access points only and does not identify the condition of the vast majority of the drainage system around a building. As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection. It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important. Even if there is no visible indication of any issues with a drainage system it is still worth considering a CCTV inspection of the system is carried out.

Below ground drainage is quite vulnerable and can become damaged in a number of ways. Ground movement, even subtle movement can result in drains becoming displaced and fractured, particularly around the joints. Tree roots can also damage below ground drains and find their way into the system. If this type of damage does occur then the surface and foul water which is usually heading toward a sewer, will actually start to discharge at the point/s where the drainage is affected. If left undetected for a period of time then vast amounts of foul and surface water can be discharged into the ground around a building, which over time can start to influence the stability of the soil, which could eventually lead to ground movement. The lesson here is always establish the condition of the below ground drainage system and deal with any problems quickly, before they become much more serious.

Adjacent Excavations - A building could sit quite happily for many years on stable ground without any problems and will only be affected if for some reason the ground conditions change. One way this could happen is works being carried out in close proximity to a building that requires excavations. If excavations are carried out to a depth and distance that could undermine or influence the stability of another building then this can cause movement, sometimes, sudden movement. This should be considered in design where it may be necessary to provide temporary support. I have encountered this on numerous occasions where ground movement has been caused by a neighbour excavating (usually foundations) and usually through ignorance has not considered the stability of their neighbours building.

Leaking Rainwater Goods (gutters and downpipes) - Even simple repair and maintenance tasks, if left unattended over a period of time can introduce large amounts of water into the ground, which can affect the soil and undermine foundations which can cause ground movement. Rainwater gutter and downpipe repairs are usually inexpensive however this is one of the most common defects that a Surveyor will encounter when carrying out inspections. Repairs to rainwater goods are usually inexpensive however if they are ignored and left for longer periods of time the consequential damage can be extensive and therefore much more expensive. The lesson here is to deal with routine maintenance and repairs sooner or pay the costs later! 

This article provides a quick overview of some of the factors that could contribute to subsidence. The points raised are not exhaustive (there are others) and you will note that no attempt has been made to discuss mining subsidence, which is a subject in its own right, perhaps for a future post.  

Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog. 

Subsidence – Part 1 – Not all it’s cracked up to be!

When you see cracking in a building it will not always be, in-fact is unlikely to be subsidence. This can only be established through a comprehensive building survey and detailed investigations

Source: Simply Business

As a Building Surveyor, when inspecting buildings I have learned over the years to be very cautious in the terminology I use in the presence of Clients because there are some words that just provoke panic. Take asbestos for example, or cracking or even subsidence. These words strike fear into many people mainly as a result of what they have seen in the news or read in the media. It is fair to say that sometimes these fears can be realised if any of the above examples are found to be present/occurring in a building, however in the vast majority of cases, these issues can be dealt with relatively easily. This is generally a result of a lack of real understanding, which is why it is always advisable to seek professional advice from a Building Surveyor or other relevant professionals.

When I first graduated from University I joined a Property Consultancy who’s main area of business was dealing with subsidence insurance claims as Loss Adjusters. My role was to visit site with a more experienced Structural Engineer, who would make an initial assessment, and then I would be required to manage the claim to a conclusion. This often involved crack monitoring to establish whether any movement was historic (had now stopped) or progressive (was still continuing). This was a crucial part of the process as it is pointless dealing with the effect of subsidence until movement has been stopped. On the occasions where movement was found to be progressive, it was sometimes first necessary to undertake substantial remedial work such as underpinning to stabilise the building. In these instances, the whole process could be lengthy and disruptive for the residents and in some cases required temporarily decanting of the occupants to alternative accommodation for the duration of the works. Most home insurance policies will cover subsidence risk and incorporate an excess payment in the region of £1000 (always check the wording of your policy because there can be variations). This demonstrates that the effects of subsidence can be disruptive and even though it may be covered by home insurance it can still be expensive.

Source: own

The above scenario provides an example of what can happen at one end of the scale, however as already stated the vast majority of subsidence claims I managed were dealt with quickly and with minimal disruption, many proving not to be subsidence at all. When undertaking building surveys, a Surveyor will not just identify where and why subsidence has occurred, but also look for indicators that may contribute to subsidence in the future. Before providing you with details of what I would look for during a survey (this will be provided in part 2 of the article), I think it is important to first understand exactly what subsidence actually is.

Building design should involve careful consideration of the type/load of the building, the type of foundation used and ground bearing capacity and nature of the ground, the height of the water table and so on. These types of investigations should help to ensure that once the building is complete and occupied that it does not move!  Subsidence however is not the same as settlement. Settlement usually occurs in new or relatively new buildings. As buildings are very heavy they cause the ground to compact, although this will usually stop after a short period of time.  Also, most buildings are constructed in a variety of materials, all of which need to settle and in addition will have different rates of shrinkage.  Subsidence occurs when for some reason the load bearing capacity of the ground that a building is placed upon is no longer capable of accommodating that load. The reasons for the change is the load bearing capacity is impacted and this can occur for many different reasons and in some cases, many years after the building was first completed. It is quite feasible for a building to sit quite happily on a piece of ground for many years and due to some of the influences discussed it part 2 of this article, it can start to move.

Cracking in buildings occurs for many different reasons so it is fundamentally important that anyone who undertakes inspections or gives advice in respect of cracking should not make rash judgements and should gather all of the evidence before arriving at a possible cause. In order to aid the inspector, which as stated previously, can be a Building Surveyor, it might be necessary to recommend other investigations such as geo-technical surveys to establish ground type, composition, contaminants etc., trial holes to establish foundation depths, CCTV inspection of the drainage system and possibly an arboricultural survey to give advice on any trees that may be an influencing factor. The choice of which investigations are needed will be decided once the inspector has made an initial assessment of the cracking.  Therefore, when you see cracking in a building it will not always be, in-fact is unlikely to be subsidence however, this can only be established through a comprehensive building survey and detailed investigations.

In Part 2 of this article I will discuss subsidence in more detail and provide information of the things a Building Surveyor will look at to identify when and how subsidence is occurring as well as indicators that may suggest that subsidence can occur in the future.


Author: Gary O’Neill

Please feel free to share this article and other articles on this site with colleagues, friends and family who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

House hunting? - Look beyond the decorations!

No matter what the condition or quality of the decorations and other finishes, most people will usually re-decorate to their own taste anyway.  It is important that your mind is focused on looking beyond this, which will allow you to focus on the condition and layout of the building

Source: www.ibtimes.co.uk

Throughout my career as a Building Surveyor I have been lucky enough to have undertaken many different types of surveys of all types of buildings both large and small and in varying degrees of condition. This experience has given me the ability to identify 'possible issues' in a building without undertaking an intrusive inspection. In simple terms if you know where to look and what to look for, you can quickly establish issues that may need much closer attention.

Whilst house hunting fairly recently and viewing properties for the first time you may be surprised to learn that even as a Chartered Building Surveyor I am in the same boat as everyone else. Most properties that my wife and I recently viewed were both occupied and furnished and for a first viewing most sellers would expect a quick tour of the building followed by few questions. I think they would be a little shocked if I walked in with my surveying equipment and then started to systematically take their house to pieces so that I could decide if it was worth returning for a second visit! Something tells me that even if I wanted a second viewing the seller is unlikely to want me back! Even though my natural instinct is to be more intrusive I have to extend the same courtesy as anyone else.

Source: www.repointer58.com

When undertaking the viewing (notice the term 'viewing' and not 'inspection') there are some key things that I look for which will give me a good idea of the general condition of a building. Although I would always advise anyone to have an inspection carried out be a qualified surveyor I also thought it would be worth sharing some tips, so that those with limited or indeed no knowledge of buildings may at least be able to identify issues that they could question and bring to the attention of their advisers. This basic knowledge could also be a deciding factor which may lead to a decision not to pursue a particular property and to focus your attention on others.

Externally, I will always look at the condition of the external walls for signs of cracking, distortion (possibly bulging) and also the condition of the materials generally.  Cracking and/or distortion can occur for many different reasons and the consequences can sometimes be very serious.  It is however worth noting that if cracking or distortion in an external wall is noted that it could be historic and less significant than the damage may suggest.  There is a natural reaction by many people to panic when they see cracking in a building, however in many cases the problem can be rectified reasonably quickly and cheaply.  If you do identify cracking in a building it is always worth obtaining professional advice to arrive at an accurate prognosis.   Also, look out for signs of 'new' pointing.  Pointing refers to the horizontal and vertical mortar joints that 'bond' the masonry units together.  If you see a slightly lighter (in colour) or a different colour, area of pointing, particularly if this is in a vertical stepped position, this would suggest that recent cracking may have occurred and the cracking has been infilled.  Again, bring this to the attention of your professional advisor.

External ground levels should also be looked at closely, particularly at the junction of external walls. A damp proof course is installed in external perimeter walls to prevent moisture rising through masonry by capillary action and into a building.  Current Building Regulations require the damp proof course to be installed 150mm above external ground levels. The importance of the damp proof course is often not appreciated and you will often see raised flower beds installed abutting external walls, new driveways installed at a higher level that previously and render being applied to walls.  All of these have the potential to 'bridge' the damp proof course and provide an easy path for moisture and damp to find its way into a building.

When viewing internally it is important to look beyond the internal decorations and furnishings. Everyone has different tastes and often the conversation after the viewing can focus on 'that hideous room' or 'those awful carpets'!  This however is missing the point.  No matter what the condition or quality of the decorations and other finishes, most people will usually re-decorate to their own taste anyway.  It is important that your mind is focused on looking beyond this, which will allow you to focus on the condition and layout of the building. Try to focus on the potential of a house and this will open your mind up to think about what you can do rather than what you do not want to do.  In the whole process of buying a house, decorations and furnishings should be the least of your concerns, given that there are so many other serious problems that could arise.

Internally, you should look closely at the internal wall surfaces for signs of dampness.  This will include visible damp patches, peeling or flaking paint or possible peeling wallpaper. Dampness can occur in a building in many ways such as rising damp, penetrating damp and also condensation. In ground floor rooms pay particularly close attention at low level especially on the inside surface of external walls. Any damp identified above a metre and a half above ground level, will not be rising damp and may be a result of leaking plumbing or possible damp penetration from poorly maintained gutters and downpipes.  It is not uncommon for condensation mould to be present, especially in kitchens and bathroom.  This is due to the activity and subsequent high concentrations of water vapour in these rooms. Condensation could suggest poor ventilation, poor thermal insulation to external walls or possibly inadequate heating, or a combination of these.

If you identify dampness or cracking during your visit then bring these to the attention of your professional advisers. Hopefully the above information will help those who are unfamiliar with buildings to identify some warning signs that would suggest further investigation.  A Surveyor will undertake a detailed and comprehensive survey, if instructed, and this will provide you with an explanation of the condition of a building together with the likely cause and recommended remedial works.  So if you undertake a viewing and you identify some of the issues discussed above you may decide not to pursue that particular house any further or to seek further professional advice.

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

What's the crack? The importance of correct diagnosis of cracking in buildings

Due to the many different factors that can contribute to cracking, this is one of the most easily mis-diagnosed defects that can occur in buildings.

Source: www.eapenvoy.co.uk

When cracking is identified in a building the usual reaction is one of alarm and sometimes panic. Over the years as a Building Surveyor I have learned to be very cautious in diagnosing the cause of cracking, because it is necessary to fully understand the underlying factors that are causing it to ensure that an accurate and appropriate solution is recommended.

Cracking in a building can occur for a variety of reasons and sometimes there maybe a combination of factors that contribute to the problem.  For example drains could be damaged allowing surface or foul water to permeate into the sub-soil below a foundation.  Over time the soil will start to erode and the rate of erosion will depend on the type of soil (e.g granular soil will be more vulnerable than other types of soil), climatic condition, location etc. It is clear that the drainage will need to be rectified to ensure that the surface or foul water, finds its way through the drainage system correctly. However, what has caused the problem to the drains? Are there tree roots in the drains? Are there other trees in close proximity? Has the ground under the drains been affected in some way (i.e nearby excavations)? Is there a damaged rainwater down pipe or guttering in close proximity to the drains that are allowing large volumes of water into the sub-soil, particularly for shallow drainage? etc.etc. 

Source: own

It is therefore fundamentally important that anyone who undertakes inspections or gives advice in respect of cracking in buildings should not make rash judgements and should gather all of the evidence before arriving at a possible cause. In order to aid the inspector, which can be a Building Surveyor or Structural Engineer, it might be necessary to recommend other investigations such as geo-technical surveys to establish ground type, composition, contaminants etc., trial holes to establish foundation depths, CCTV inspection of the drainage system and possibly an arboricultural survey to give advice on any trees that may be an influencing factor. It may also be necessary to undertake monitoring of the crack to establish whether movement is still occurring. For cracking of a less significant nature these types of investigations might not be necessary at all. The choice of which investigations are needed will be decided once the inspector has made an initial assessment of the cracking.

Not all cracking in buildings is serious, which is why it is so fundamentally important to diagnose the cause correctly.  In some situations remedial measures may be as simply as rake out and re-point mortar joints, or possibly a technique called 'stitch repairing', which is basically raking out horizontal bed joints every five or six courses either side of a crack and installing steel bars which are set in epoxy resin (see video below). After the resin has cured the bed joints are simply re-pointed. At the other end of the scale however remedial measures  could be much more substantial and include underpinning or possibly even partial or even full demolition and re-build.  Therefore it is clear that the costs of dealing with cracking in buildings is extremely wide ranging, and mis-diagnosis could result in either undertaking repairs that may not have been necessary (which can be very expensive), or not dealing with the problem appropriately, with the cracking re-occurring.

I sometimes have a rye smile when I watch property programmes such as Homes under the Hammer. It is interesting to hear the presenters talk about defects that 'they have discovered' when they visit the various properties, particularly cracking.  You can bet that they will say, 'that could be serious and needs checking out', they obviously do not have a clue what the cause of the problem actually is. What is even funnier is when they ask the purchaser if they were aware of the cracking when they had bid for the property and they will always say 'yes, but we had it checked out and it is nothing serious!'. In all of the many episodes of that programme that I have seen over the years I have never heard any purchaser be perfectly honest and admit that the cracking was serious and had cost them a fortune! I suppose it is because they do not want to admit too being a complete fool on national television!

The subject of cracking in buildings is extremely wide ranging and it is not the purpose of this article to try to consider every aspect, in fact there are numerous books and other publications that cover the topic extensively.  What is important however is that when cracking occurs that the reasons for it are fully investigated and understood so that appropriate remedial works can be carried out.  Due to the many different factors that can contribute to cracking in buildings, this is one of the most easily mis-diagnosed defects that can occur.  It would therefore seem sensible to seek the advice of a professional at the earliest opportunity. Although this advice may have a cost attached, it could prevent a much higher cost in the future.

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog. 

Subsidence – Part 2 – Factors that contribute to subsidence and what to look for

As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection.  It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important

Source: http://www.users.globalnet.co.uk/

In last week’s article I gave an example of the consequences of building subsidence, which can be extremely disruptive and expensive to deal with, however I also emphasised that the vast majority of subsidence damage is less serious and can be rectified reasonably easily.  I also identified that to the average householder the mere mention of the word subsidence strikes fear and panic into them as there is a perception that subsidence damage is always serious. As you would expect and as I have mentioned many times before, if you are thinking of purchasing a property it is always advisable to have a professional, such as a Building Surveyor, inspect the building before you commit to buy.  The Surveyor’s report will identify any issues that are present and inform you if any are serious.  A Building Surveyor will also highlight factors that may contribute to subsidence in the future and not just focus on the here and now.  There are a number of factors that could lead to subsidence and some examples are discussed below:

Clay Soils

To support a building it is essential that the load bearing capacity of the ground is capable of supporting the dead load of the building (the building’s self weight) as well as any imposed load (furniture, fitting, people, snow etc.), once completed and occupied.  The type of ground is essential to a building’s stability as this will determine the most appropriate as well as the depth of the foundation that should be used.  When siting a building, clay soils are particularly problematic compared to most other types of soil because clay has the ability for significant volumetric change depending on how much water/moisture it contains at any particular time.  When clay is wet it will swell and therefore expand, however when the ground starts to dry out all of this moisture is slowly removed and the clay will shrink.  Think about this process happening with a building on it!  If the ground is constantly expanding and then shrinking, then it is inevitable that the weight of a building will eventually be effected by these changes and cause the building to move.  Having said the above there is no reason why a building cannot be constructed on clay as long as this is established through ground investigations and appropriately catered for in the design.  This may involve deeper foundations, as well as the inclusion of root barriers where trees and vegetation may be in close proximity to the building.

Trees

Source: http://pipe-repair-woollahra.street-directory.com.au/

Whilst inspecting a property, as well as focussing on the building itself I would always look very closely at the surrounding environment and in particular the size and location of trees.  If not managed, trees and in particularly their roots have the ability to undermine foundations, damage drains and cause significant damage to a building.  The problem with tree roots is that you often cannot see the extent of the root growth or proximity to the building because they are buried.  This however does not mean that they should be ignored and where trees are deemed the pose a threat to a building then the services of a tree expert (Arboriculturist), should be called upon.  This is necessary because different species of tree will exhibit different characteristic in terms of size, growth rate, root spread etc. in addition to advice that can be provided in respect of the condition of trees and any recommended remedial action.

Tree roots do a number of things when in the ground.  Firstly they take up large amounts of water from the ground.  Given what has been discussed above in respect of clay soils you can easily see that in continued spells of warm weather and high temperatures that clay soil and tree roots are not a good combination and together this will significantly increase the potential for subsidence.  Secondly, as the roots grow they have the ability to physically impact on soils, particularly soft/granular types which can undermine stability especially when they have a foundation and a building siting upon them.  Also, as can be seen below tree roots have the ability to damage below ground drainage.

Drainage

Although it is possible to make a broad assessment of a drainage system during an inspection, by lifting manhole/inspection chamber covers this is limited to a small number of access points only and does not identify the condition of the vast majority of the drainage system around a building.  As with tree roots, a drainage system is buried therefore not obviously visible at the time of an inspection.  It always amazes me how people tend to ignore the condition of the below ground drainage system when purchasing property and do not seem to see this as important.  Even if there is no visible indication of any issues with a drainage system it is still worth considering a CCTV inspection of the system is carried out.

Below ground drainage is quite vulnerable and can become damaged in a number of ways.  Ground movement, even subtle movement can result in drains becoming displaced and fractured, particularly around the joints.  Tree roots can also damage below ground drains and find their way into the system.   If this type of damage does occur then the surface and foul water, which is usually heading toward a sewer, will actually start to discharge at the point/s where the drainage is affected.  If left undetected for a period of time then vast amounts of foul and surface water can be discharged into the ground around a building, which over time will start to influence the stability of the soil, and eventually lead to ground movement.  The lesson here is always establish the condition of the below ground drainage system and deal with any problems quickly, before they become much more serious.

Adjacent Excavations

Source: www.thesun.co.uk

A building could sit quite happily for many years on stable ground without any problems and will only be affected if for some reason the ground conditions change.  One way this could happen is works being carried out in close proximity to a building that requires excavations.  If excavations are carried out to a depth and distance that could undermine or influence the stability of another building then this can cause movement, sometimes, sudden movement.  This should be considered in design where it may be necessary to provide temporary support. I have encountered this on numerous occasions where ground movement has been caused by a neighbour excavating (usually foundations) and usually through ignorance has not considered the stability of their neighbours building.

Leaking Rainwater Goods

Even simple repair and maintenance tasks, if left unattended over a period of time can introduce large amounts of water into the ground, which can affect the soil and undermine foundations which can cause ground movement. Rainwater gutter and downpipe repairs are usually inexpensive however this is one of the most common defects that a Surveyor will encounter when carrying out inspection. 

The article above provides a quick overview of some of the factors that could contribute to subsidence.  The points raised are not exhaustive (there are others) and you will note that no attempt has been made to discuss mining subsidence, which is a subject in its own right, perhaps for a future post. 

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Subsidence – Part 1 – Not all it’s cracked up to be!

When you see cracking in a building it will not always be, in-fact is very rarely likely to be subsidence.  This can only be established through a comprehensive building survey and detailed investigations

Source: http://www.subsidenceforum.org.uk/

Whilst inspecting buildings I have learned over the years to be very cautious in the terminology I use in the presence of Clients because there are some words that just provoke panic.  Take asbestos for example, or cracking or even subsidence.  These words strike fear into many people mainly as a result of what they have seen on the news or read in the media.  It is fair to say that sometimes these fears can be realised if any of the above examples are found to be present/occurring in a building, however in the vast majority of cases, these issues can be dealt with relatively easily.   This is generally a result of a lack of real understanding, which is why it is always advisable to seek professional advice from a Building Surveyor or Structural Engineer.

When I first graduated from University I joined a Property Consultancy who’s main area of business was dealing with subsidence insurance claims as Loss Adjusters.  My role was to visit site with a more experienced Structural Engineer, who would make an initial assessment, and then I would be required to manage the claim to a conclusion.  This often involved crack monitoring to establish whether any movement was historic (had now stopped) or progressive (was still continuing).  This was a crucial part of the process as it is pointless dealing with the effect of subsidence until movement has been stopped.  On the occasions where movement was found to be progressive, it was often first necessary to undertake substantial remedial work such as underpinning to stabilise the building.  In these instances the whole process could be lengthy and disruptive for the residents and in some instances required temporarily decanting of the occupants to alternative accommodation for the duration of the works.   Most home insurance policies will cover the risk of subsidence and incorporate an excess payment in the region of £1000 (always check the wording of your policy because there can be variations).  This demonstrates that the effects of subsidence can be disruptive and even though it may be covered by home insurance it can still be expensive.

Source: http://www.geoconsult.co.nz/

The above scenario provides an example of what can happen at one end of the scale, however as already stated the vast majority of subsidence claims I managed were dealt with quickly and with minimal disruption, many proving not to be subsidence at all.  When undertaking building surveys, a Surveyor will not just identify where and why subsidence has occurred, but also look for indicators that may contribute to subsidence in the future.  Before providing you with details of what I would look for during a survey (this will be provided in part 2 of the article), I think it is important to first understand exactly what subsidence actually is.

Building design should involved careful consideration of the type/load of the building, the type of foundation used and ground bearing capacity and nature of the ground, the height of the water table and so on.  These types of investigations should help to ensure that once the building is complete and occupied that it does not sink!  Subsidence however is not the same as settlement.  Settlement usually occurs in new or relatively new buildings. As buildings are very heavy they cause the ground to compact, although this will usually stop after a short period of time.  Also, most buildings are constructed in a variety of materials, all of which need to settle and have different rates of shrinkage.  Subsidence occurs when for some reason the load bearing capacity of the ground that a building is placed upon is no longer capable of accommodating that load.  The reasons for the change is the load bearing capacity can occur for many different reasons and many years after the building was first completed.  It is quite feasible for a building to sit quite happily on a piece of ground for many years and due to some of the influences discussed it part 2 of this article, it can start to move.

Cracking in buildings occurs for many different reasons so it is fundamentally important that anyone who undertakes inspections or gives advice in respect of cracking should not make rash judgements and should gather all of the evidence before arriving at a possible cause.  In order to aid the inspector, which as stated previously, can be a Building Surveyor or Structural Engineer, it might be necessary to recommend other investigations such as geo-technical surveys to establish ground type, composition, contaminants etc., trial holes to establish foundation depths, CCTV inspection of the drainage system and possibly an arboricultural survey to give advice on any trees that may be an influencing factor.  The choice of which investigations are needed will be decided once the inspector has made an initial assessment of the cracking.  Therefore when you see cracking in a building it will not always be, in-fact is very rarely likely to be subsidence.  This can only be established through a comprehensive building survey and detailed investigations.

In part 2 of this article (next week) I will discuss subsidence in more detail and provide information in respect of the things a Building Surveyor will look at to identify when and how subsidence is occurring and indicators that may suggest that subsidence can occur in the future.

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