Subsidence is the downward movement of a building foundation caused by loss of support of the site beneath the foundatio
Problems with your house? Cracks?
GENERAL LINE OF FRACTURING
WIDE
Subsidence? Heave?
NARROW
POSITION OF LIKELY MAXIMUM SUBSIDENCE
CRACKS CONTINUE AROUND OPENINGS
Get the right advice! What are settlement, subsidence and heave? Settlement is the normal downwards movement of a building into the
ground simply as a result of its own weight on the ground. Most new buildings experience some minor settlement during the first year or two after construction until they finally stabilise. If major structural alterations are carried out on an existing property, again some minor settlement may occur while the ground readjusts itself to the new weight pattern of the property. Settlement may cause minor cracking but this is usually not serious or progressive.
Subsidence is the downward movement of a building foundation caused
by loss of support of the site beneath the foundation. In other words, subsidence is caused by the ground moving away from the underside of the foundations of a property. This may be due to a variety of reasons which are explained later in this leaflet.
Heave is, in simple terms, the opposite of subsidence and is caused by the ground pressing up against the foundations of a property and forcing the foundations upwards.
The effect of subsidence or heave on a property is that it may develop cracks or may distort - sometimes it does both.
Why are subsidence and heave important for householders? Over the last 30 years or so properties affected by subsidence have proved difficult to sell, but things have started to change. Nevertheless, lenders and insurers are still cautious about properties that display evidence of movement. If you are likely to want to sell your property then it is important to have any subsidence or heave damage assessed, and attended to if necessary. This is best done sooner rather than later because if the problem is only identified when you are selling or buying, it may cause serious delay to your transaction. Like fire, escape of water or storm damage, subsidence and heave are standard risks covered (subject to policy wording) by the majority of domestic building insurance policies, although sometimes damage to ground bearing concrete slabs or fences or garden walls are not covered. Indeed for owners who have mortgages, it is usually a compulsory requirement of the terms of the loan that the property is insured against certain risks, including subsidence and heave. Settlement damage is not normally covered by household insurers.
What causes subsidence and heave? Subsidence is much more common than heave. The most common causes are: -
Drying out and shrinkage of clay subsoil beneath the house foundations during drought periods, such as exceptionally hot summers. Heave is normally caused by the swelling of clay during wet winters after hot summers.
- The effect of certain types of trees close to a property which can aggravate the subsidence/heave situation where clay subsoil exists. - Leaking drains and water mains can soften the ground beneath house foundations, or even wash away the material from beneath the foundations, thus causing subsidence. - Properties built close to sloping ground may suffer subsidence if the ground tends to move down the slope – even if the movement of the slope is only slight! - Chalk ground can develop cavities (swallow holes) and cause subsidence. - Mining can cause subsidence to property above and adjacent to the works.
How can subsidence/heave be dealt with? The first step is to establish that the damage is actually due to subsidence or heave. Buildings can suffer movement and cracks for many other reasons, for example due to thermal movement or differential settlement. If subsidence or heave is the cause of the damage, then three questions should be asked: -
Has the movement stopped? If it has, there is clearly no point carrying out any work other than making good the cracks and then redecorating, but the fact that it has stopped will have to be confirmed by a suitably qualified and experienced expert. This may require the property being monitored for a specified period - but usually for no more than 12 to 24 months.
- If movement is continuing, can the cause be identified and attended to? Perhaps only drain repairs or tree management is required – this is cheaper and much less troublesome than underpinning. - Finally, is there any alternative to underpinning the affected part of the property? Underpinning is expensive, disruptive and time-consuming so, if possible, it should be avoided. Irrespective of which option is adopted, a new insurer (and a future mortgage lender) will want confirmation from a technical expert that the problem has been investigated thoroughly and that further structural movement is unlikely before they accept continuing or future liability for the property.
Should you tell your insurer if you suspect your property is suffering from subsidence or heave? If you note any evidence internally or externally to suggest your property is suffering from subsidence/heave movement, you should inform your insurance company immediately. It is a condition of most insurance policies that prompt notification is required. This is also sensible because the sooner the problem is investigated and dealt with, the less inconvenience and cost will be involved.
Should you tell your mortgage lender (building society, bank)? Not normally, as your lender will refer the matter to your insurer, but certainly start by informing your lender if you are not sure who your insurer is.
What will happen when you report it? Your insurer will require you to fill out a claim form and will appoint an experienced technical expert to investigate the claim. Such an expert is likely to be either a Loss Adjuster or a Chartered Engineer, or both.
Will you have to pay anything towards the investigation? Like car accident claims, subsidence claims have an excess, at present most insurers limit this to the first £1000 of the cost of the work actually carried out on the property. Very rarely does an insurance company charge a householder for the actual investigation of the claim by the insurer; that is usually done at the insurer’s expense. Typical remedial work carried out might be repair of drains, felling or pruning tress, underpinning foundations, redocoration, etc. Provided you are adequately insured in accordance with your policy, the insurer usually pays everything above the excess.
Will the value of the property be reduced because it has suffered from subsidence? Nobody can guarantee the value of a house; 20 or 25 years ago it would frequently be the case that a property which had suffered from subsidence/ heave was significantly down valued, even when underpinning or other foundation remedial works had been carried out. This is less likely to be so now because insurers and lenders are more knowledgeable about the effects of subsidence/heave and how to deal with them.
Will you be able to sell the property if it has suffered from subsidence/heave? Guarantees that further subsidence/heave will not re-occur can never be given, but there is no doubt that a property which has been professionally investigated and for which a reasonably conclusive expert report is available is likely to be sold much more easily than one which has not been investigated and reported upon. A summary of the report’s findings should be contained in a Certificate of Structural Adequacy (CSA) issued by the expert on completion of the investigation and of any remedial works.
Is there anything which you can do to minimise inconvenience and problems when you do come to sell? If your property has suffered from subsidence or is likely to do so then it is advisable to remain with your present insurer. Once insurance cover has been removed from a property which has had subsidence/heave, it is often very difficult to get insurance cover reinstated and this will definitely affect a potential sale. If your property has suffered from subsidence/heave and this has been investigated and dealt with and a CSA is available, that is very useful. Usually existing insurers are then prepared to continue insurance on the house to the new purchaser. This means that the house has insurance which the purchaser’s lender will consider essential before granting a mortgage to the new owner.
Will you have to reduce the price of your property to sell it if it has suffered subsidence/heave? This will depend very much on the market for houses at the time that you come to sell, but any difficulties or price reductions may be minimised by: - Existing subsidence insurance continuing through the sale to the new owner, and - An expert report and CSA giving your property a clean bill of health after the problem has been appraised, and if necessary dealt with.
Who will advise you? The contract of insurance is between yourself (as the householder) and your buildings insurance company. Normally your insurance company will appoint the expert and pay for that expert to investigate the alleged subsidence/ heave. If you wish to appoint your own ‘expert’, then obviously you are quite free to do so, but you should make sure that you do appoint someone who is experienced in investigating subsidence/heave. You should seek the insurance company’s approval for the use of your expert or you may find that you have to pay the fees of your own expert without being able to claim them back from your insurer. If you disagree with what the insurance company appointed expert says, you may feel justified in getting your own ‘second opinion’.
Should you chop down your trees? There is no point in chopping down trees unless they are causing the problem, or are likely to do so. Even if there are trees nearby not all ground conditions are such as to result in subsidence. The local authority may have a Tree Preservation Order on your trees and it would, therefore, be illegal to remove or seriously damage the trees without permission. Trees also add quality to an area, so removing them may detrimentally affect the value of your property. In any event, it is probable that you will only be able to remove your own trees - you may not remove neighbour’s or Local Authority trees without their permission. The best approach is not to heavily prune or remove your own trees until you have received expert advice. Your neighbour may have trees which could be just as much of a threat to your property. If the ground beneath your property is susceptible to movement because adjacent trees have extracted moisture from it, then removal of the trees may result in heave of the ground. This can also be damaging to the property, so expert advice is essential.
Should you water the ground around your trees to provide them with the moisture which they require during hot weather? During droughts the authorities normally forbid householders to use water on gardens. In addition, the mechanism by which water passes into clay ground and is then abstracted by root systems is complex. You will probably be wasting your time watering the ground.
Should your drains be tested and repaired? Get expert advice before you undertake any work on your drains - it may not be necessary.
Should you appoint a Structural Engineer to advise? Make sure the person you appoint has the appropriate experience. Structural Engineers are generally considered to be the most appropriate experts to advise on subsidence/heave matters, but not all people who claim to be Structural Engineers are members of the Institution, nor do all members of the Institution necessarily have experience of dealing with subsidence/ heave. To ensure that the person you are dealing with is a genuine structural engineer with knowledge of subsidence/heave ask for proof of their experience or visit www.findanengineer.com This is the Institution’s website where only companies with at least one member of the Institution can register their details. The Institution of Structural Engineers has made a special study of the subject and has published recognised authoritative advice. Subsidence of low-rise buildings is available from the Institution’s website www.shop. istructe.org. Some qualified members of other professional Institutions, such as the Institution of Civil Engineers and the Royal Institution of Chartered Surveyors, are also experienced in dealing with subsidence and heave. Further information: The Institution of Structural Engineers 11 Upper Belgrave Street London SW1X 8BH tel +44(0)20 7235 4535 | fax: +44(0) 7235 4294 email
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