Subsidence
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The use of the word subsidence will often cause an unnecessary fear amongst homeowners. Many will assume that the building is subsiding when they see cracks appear and in most cases the cracks are the result of natural shrinkage and the normal movement of the building. Buildings will move if the subsoil dries excessively as it did in the hot dry summer of 1976, yet this is not a reason to have expensive underpinning work done. Normally, we can expect that when the soil regains its normal moisture content and the water tables resume their normal level the cracking will stop and usually close up again. Subsidence is when changes underground cause foundations to shift and stop supporting the walls, as they should. When buying a new property your Survey will include looking for any signs of subsidence and investigating any previous records of underpinning or corrective repairs caused by |
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subsidence. You can also use web-site www.homecheck.co.uk and enter the postcode for the property to get a report of the area for subsidence, flooding, pollution etc. free of charge. Your Surveyor’s Report will cover any signs of subsidence and recommend any further investigation if felt necessary. If you are a current homeowner and you are worried about cracks appearing or getting bigger then contact a local surveyor either through the Yellow Pages or ask your Insurer to recommend one in your area to look and report on the situation.
Cracks in internal walls are often the result of the gypsum plaster drying out and this is very noticeable in new properties. External cracks often in cement rendering are due to shrinkage. Because the rendering is too strong for the wall beneath, the rendering will crack and sometimes fall off. This will allow water to penetrate into the brickwork and behind the rendering causing increasing problems of damp. My recommendation in this situation if seen, should be addressed quickly.
Cracking can also be caused by vibrations either from traffic or may be nearby building work. Cracks often appear around door openings due to the door being slammed. All these things are NOT subsidence! If a crack continues to get wider and longer, and is widest at the top and if the crack goes across bricks diagonally i.e. breaks them in two, and not around them following the mortar joints then this is potentially more serious. Also if doors and windows become difficult to open and close, then in these circumstances a surveyor should be employed to look at the situation.
How can you establish whether a house maybe at risk?
Areas of the country where mining or tunnelling has be going on should be viewed as higher risk - so should areas that have flooded in the past and areas where property has been constructed on landfill sites. A property that is close to a watercourse can be higher risk, as would be a property with forest trees close to the buildings. If there is no problem with close trees do not chop them down as the water content of the soil can change dramatically and one can initiate a problem like “heave” which is the reverse of subsidence i.e. the ground rising and swelling with excess moisture.
Property built upon clay soils will be more subject to movement due to shortage of or an excess of moisture in the ground. Leaking drains are one of he main causes of true subsidence and unless corrected quickly increasing damage to the structure will most likely occur.
Where subsidence has been identified then a Loss Adjuster, who will be a qualified engineer and appointed by the Insurance Company, will decide what needs to be done.
Usually the first thing is to have devises, which monitor movement, fixed to the walls. They will show if there is progressive movement and how severe it is. The monitoring can last many months and at the end the Loss Adjuster’s Report will state what needs to be done.
If underpinning is necessary, this will involve the removal of soil under the foundations and the walls supported, whilst either deeper foundations are built or the whole cavity is filled with concrete up to the underside of the existing foundations. The cause of the subsidence will have to be rectified i.e. leaky drain relined, watercourse diverted, improved surface water disposal etc.
Your Insurance Company will appoint the contractors and supervise the work. All structural and superficial damage will be repaired and the property returned to its pre-damaged condition.
Most home insurance building policies are covered for Subsidence. However, you need to check what your excess level is, i.e. what amount do you have to pay before the Insurance Company pays the remainder. Normally the excess on Subsidence is about £1,000 but you need to check this and also check if your outbuildings and garden walls are covered by the policy. Read the small print for exclusion clauses and if in any doubt talk to your Insurer or Insurance Broker.