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Did the earth move for you?

TEAM Property Matters article, p11, Property Matters, UK Issue No 1 Spring 2000 www.teamprop.co.uk
Philip Rougier is independent of Team and Property Matters.

This is the text of the original article,
updated and with additional information.
Just click the links to discover more!

If you suspect subsidence, don't ignore it and hope no-one will notice,
says defects specialist Philip Rougier

If you know, or even suspect, that your property has undergone subsidence, it is much wiser to act than ignore it. Valuation surveyors are increasingly twitchy about cracks, bulges and window/door joinery distortions, commonly referring such problems to a specialist. Faced with a choice, they would rather delay your sale than risk a negligence claim. This can capsize the transaction at its most critical stage, usually for months, sometimes years.

The good news is that there are many conditions that give subsidence-like symptoms, and a knowledgeable defects specialist will discover whether the true cause is something else - such as roof spread, wall slenderness, shrinkage/expansion (thermal or materials-based), lintel failure, weathering effects, etc. Some subsidence conditions are very localised - for example, that caused by a water mains or drains leak. Others are more general - perhaps due to clay soil expansion/contraction, or a rise/fall in water table.

If you deal with it early, you will have all the right pieces of paper in place when you sell. Reports on drains, soils investigation, specification, a completion certificate, etc, will help satisfy your purchaser's surveyor, mortgage lenders and (above all) insurers, who should continue to insure the property for the new owner.

The good news is that there are many conditions that give subsidence-like symptoms, and a knowledgeable defects specialist will discover whether the true cause is something else - such as roof spread, wall slenderness, shrinkage/expansion (thermal or materials-based), lintel failure, weathering effects, etc. Some subsidence conditions are very localised - for example, that caused by a water mains or drains leak. Others are more general - perhaps due to clay soil expansion/contraction, or a rise/fall in water table.

If you deal with it early, you will have all the right pieces of paper in place when you sell. Reports on drains, soils investigation, specification, a completion certificate, etc, will help satisfy your purchaser's surveyor, mortgage lenders and (above all) insurers, who should continue to insure the property for the new owner.

If you leave things, perhaps in the hope that it won't be noticed, there is every chance that the problem will be discovered. And even if your buyer's valuer misses it, there is a serious risk that you could be held liable later on if it emerges that you knew and didn't disclose.

Often your buildings insurers will pay for the cost of underpinning, drains repairs and making good, and the professional fees involved, less an "excess" - typically £1,000. This may sound a lot, but it can be so much cheaper than a price-reduction, abortive legal costs, and losing the chance to move to your next property. But do allow many months for this process!

 

TELL-TALE signs

Cracks in brickwork, render or plaster.
Window/door frame distortions (sticking).
Leaking/blocked drains (leaks can cause blockages).
Floor undulations.

 

ACTION plans

Don't change insurers!
As far as possible, date cracks and other symptoms.
Get a defects specialist who is familiar with insurance claims.
Ask for a programme, and follow it up at intervals.

 

Philip Rougier MPhil CEnv MCIOB FBEng, is a building defects specialist with much Expert Witness experience.

 www.expertexpert.com (main website)


Subsidence is defined as the downward movement of the bearing soil on which a building rests. There are many possible causes for a bearing soil to fail. It is possible for subsidence to occur progressively over a long period, to occur over a very short period and then stop, and other variations on this theme. Some valuers describe subsidence that has evidently occurred long ago, from evidence of weathered cracks and long-accommodated distortions in brickwork) as "historic".
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Valuers are qualified professionals who have studied valuation methods for commercial property, and are often connected with estate agencies. There is no formal method of calculating the market value of domestic property - it can only be done by comparing similar recent sales, known as "comparables". Qualified valuers are usually members the Royal Institution of Chartered Surveyors - MRICS/FRICS - General Practice division, usually (but not always directly) associated with an Estate Agency practice. Over the years the RICS has absorbed the Incorporated Society of Valuers and Auctioneers - ASVA/FSVA - into its membership, in a continuing EC-directed consolidation process for UK professional institutions.
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Cracks can occur in brickwork and blockwork for many reasons, and do not necessarily result from subsidence of bearing soils. Some surveyors and engineers try to apply the Building Research Establishment's guideline that cracks of 1mm or less are "insignificant", but this is only part of the story - for example, such cracks may be in the early stages of development, or represent a defect that only produces minor cracking, but is significant in some other way. It should be appreciated that cracks are symptoms.
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Bulges in external brickwork can sometimes be "as built" (ie the wall was built out of vertical from inception) but this is unusual. More usually, brickwork bulges result from inadequate lateral restraint at intermediate floor levels, effectively making the wall very "thin", or cavity wall tie failure, where the cavity wall ties have rusted through.
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Joinery distortions can give indications of subsidence movement. Internal and external door openings can develop a tapered gap at the top, with the door lining and top architrave becoming sloped. Usually, the vertical sections of the door lining remain vertical. In the early stages, small gaps may appear at the mitre joints of the architraves, initially showing as hairline cracks in paintwork. Similar movements occur in windows, although can be more difficuly to detect visually.
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Negligence is what you can sue a surveyor for, if you suffer a monetary loss. Most professional institutions require that practising surveyors must carry Professional Indemnity insurance, often with a minimum cover related to the size of their practice - typical amounts are £250,000 - £1m. If a problem is just identified by a surveyor, that is not enough - (s)he must go further and, for example, state what the consequences are likely to be. But if a surveyor gives incorrect advice, or misses a defect, (s)he is not automatically liable. Professional Indemnity actions against surveyors (in reality against insurers) are something of a mine-field, and are almost always long-winded and costly affairs, with no guarantee of a successful outcome.
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Roof spread occurs when a roof frame is not properly tied ("triangulated"), resulting in horizontal movement which pushes fascia boards out sideways, and often leaves a visible gap between the soffit board and brickwork. In extreme cases, brickwork can be pushed out at the top and the wall develops an outward curve. Roof spread happens mainly in "cut" roofs (made from sawn timber) and is usually caused by poor design on the part of the architectural designer, or site carpenter. It hardly ever occurs in trussed roofs, which are designed and manufactured in a factory and brought to site for final erection. Roof spread is not covered by standard house insurance policies, therefore the expense of remedying falls on the owner.
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Slenderness problems (the height : wall thickness ratio) are very common. Properly, a cavity wall should be tied ("laterally restrained") to floor structures at each floor level. Often this happens accidentally, where floor joists are built in to the inner skin of the cavity wall. But where the joists run parallel, there is often no connection between the two. Lateral restraint ties for this situation have become a basic Building Control requirement in recent years, but most older houses have no restraint in some walls. The remedy is to take up some floor boarding, notch the tops of the floor joists, and install long, thin, galvanised steel ties - these are built into the inner leaf of brickwork and nailed to the joists, typically at 1.8m centres.
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Shrinkage is a natural phenomenon of virtually all building materials; each with a different shrinkage rate. It it widely known that shrinkage occurs in timber, mainly across the grain and very little down its length, and this is well-known. It can be minimised by correct seasoning, but most wood is sensitive to changes in moisture, and will shrink and expand as its water content falls and rises. It is less well-known that initial shrinkage occurs in all cementitious (concrete) products - for example; concrete blocks, calcium silicate bricks, concrete slabs, mortars and plaster (render) backing coats - within the first 18 months or so after their manufacture (it tends to stop after that), which can result in the occurrence of cracks. Such effects can be avoided by installing "crack control" joints in the structure, and all manufacturers of concrete products will advise on the spacing of movement joints appropriate to the items they sell. Fortunately, shrinkage cracking is usually not very serious, although if left unresolved it can lead to other forms of damage. Thermal shrinkage and expansion is a continuing natural phenomenon of building materials, and each has a different coefficient of expansion (or contraction) - some materials move only slightly with changes in temperature (eg bricks and concrete, maybe < 3 x 10-6 per °C), others are relatively large (eg plastics, at around 60 x 10-6 per °C). In a cementitious product, when there is a combination of initial shrinkage, and continuing thermal expansion/contraction which can occur and reverse daily, cracks can get ever-wider as a result of a phenomenon known as "ratcheting" - small particles from the crack faces fall into the crack, and prevent it closing when the material cools. Therefore on each re-heating, the cracks widen slightly, starting from their new position each time. Such movements are always small, but the forces involved are very powerful, and quite large ultimate displacements have been recorded.
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Weather effects such as "freeze and thaw" (rainwater enters a small fissure, freezes, expands and widens it before melting) are common in building. Sometimes, the resultiing enlargened crack looks like a subsidence symptom. At other times the arrises of the crack are weathered by wind/rain, and not due to continuing soils activity beneath the building.
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Leaks in drains and water supply pipes can cause localised subsidence of bearing soils, with localised building disturbance immediately above the failed area. If such a condition has occurred, domestic buildings insurers might be persuaded to settle local foundation underpinning costs on an "Escape of Water" basis, rather than under the "Subsidence" head of claim - this would mean that the excess would be reduced, or removed. The insured would still have to meet the cost of remedying the cause of the leak, because this is not insured, however insurers might be further persuaded that the drainage or water supply pipework has to be necessarily disturbed to deal with foundation repairs.
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Lintel failures (or absences) result in brickwork cracks, yet are nothing to do with foundations, or subsidence of them. Remedial works are usually quite simple, but the cost must be met by the building owner as there will be no buildings insurance cover.
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Clay soil expansion / contraction problems, known to buildings insurers collectively as "heave", result from changes in moisture levels in clays that are sensitive to such changes. Some clays do not move much, others a great deal - their "sensisitivity" can be determined by testing soil samples in a laboratory. Heave problems are dealt with by domestic buildings insurers in the same way as subsidence, however remedial techniques are usually quite different. Heave solutions often require piling to a depth where the bearing soil is stable, and the installation of compressible/collapsible void formers to provide a gap between the clay soil and the structure. Heave solutions can often be very expensive.
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Rises and falls in water table can result in the collapse of soils that are sensistive to changes in water content. Some clays are very susceptible, others are relatively insensitive. Some sandy soils have particle sizes and distribution that allows "collapse" (reducing their volume, increasing their density) when wetted - alluvial river silts that are relatively "young" in geological terms and have never been overlain or re-immersed, can often do this.
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Reports on drains, soil investigation, specification, completion certificate etc should be prepared by a qualified "structural engineer", with continuity from inception to completion of the remedial works, if insurers are to be convinced that the building has returned to a "normal risk" state and continue to insure it. The term "structural engineer" is a broad one for insurers', purposes. It includes members of the Institution of Structural Engineers (MIStructE/FIStructE) of course, although not all M/FIStructE's deal with foundations or even domestic buildings. It can also include members of the Institution of Civil Engineers (MICE/FICE), Chartered Institute of Building (MCIOB/FCIOB), Royal Institution of Chartered Surveyors (MRICS/FRICS) - but only the Building Surveying Division - and the Association of Building Engineers (MBEng/FBEng). Certain other professional institutions are also acceptable to insurers. Paper qualifications are material, but the two points of most importance to your insurers are that the practitioner has (1) the requisite knowledge and skills, and (2) professional indemnity insurance for the application.
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A vendor could be held liable later for having sold property knowing it to be defective and not disclosing that information during formal sale enquiries. It is not enough to respond "rely on own surveyor" when asked this question in the Particulars of Sale form (usually completed with the help of a Solicitor). There are many ways in which a vendor owner can be on record as having become "fixed with knowledge" - for example, if they have made an enquiry at a Local Authority office, estate agency or professional practice, or perhaps a Citizens Advice Bureau. [A classic example is a Housing Repairs grant, applied for and never taken up because the owner's contribution was too great. Having sold years later, the defects were uncovered soon after purchase, and the new owner went on to discover that the vendor knew and made a false declaration.]
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Don't change insurers! - so many times, an owner changes insurers to get a nice low annual premium and a few months later decides to do something about their suspicions of subsidence. This can cause severe complications, because the original insurers have to be brought into the picture - often two Loss Adjusters are appointed, and the claim and its resolution becomes a very difficult and complicated affair.
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A transaction can be capsized at point of sale by the sudden appearance of "subsidence" in the valuer's report. Some buyers will not contemplate a property that has such a defect, however irrrational that is (they will happily drive a car that once had a flat tyre). But the sudden introduction of repair requirements can mean a serious delay in proceedings. There are ways to get around it - for example insurers can sometimes be persuaded to agree underpinning costs quickly, so that the work can be carried out during the purchase period - however everyone has to move at lightning speed to achieve this. It is always advisable to have the same insurer re-insure the building for its new owners, following remedial works completion.
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Floor undulation conditions within a house are usually not covered by domestic buildings insurance policies. They were at one time, but gradually became restricted by insurers ("occurring at the same time as foundation subsidence, from the same cause, etc etc") and in more recent years they have been specifically excluded by many policy writers. The basic reason is that floor subsidence is often found to be due to poor construction techniques (inadequate excavation, incorrect fill materials, inadequate compaction, etc) and not a true subsidence issue in which the native bearing soil failed.
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