Categories 4 and 5 damage will probably require a specifi c remedy in addition to above-ground repairs. There is a likely need for some type of underpinning in these cases.
It should be mentioned at this stage that some settlement in certain structures is quite normal, being due either to the initial consolidation of the building after construction or to long-term consolidation over the life cycle. A BRE Current Paper, ‘ Settlement of a Brick Dwellinghouse on Heavy Clay, 1951 – 1973 ’ , CP 37/74, on this topic covered a 20-year history of settlement in the narrow strip foundations of a typical house in Hemel Hempstead, Hertfordshire. This settlement was found to continue fairly steadily for the whole period (without causing any cracking to the walls) at rates of between 0.12 and 0.39 mm/year, with angular distortion of the foundations to 0.1%. More-brittle wall Lateral expansion
39
surfaces, especially surfaces with a smooth stucco, would have cracked as a result of such angular distortion causing Categories 1 or 2 damage, but of itself this would not have been signifi cant.
The question of which category in which to place a specifi c observed area of damage is very much a matter of judgement. A large number of narrow cracks may, in some cases, be more signifi cant than a few larger ones. The recommendations for categorising damage can be no more than a guide, and each property and area of damage has to be
Assessment of Damage
Compression
41
individually assessed on its merits. Having decided initially on the extent of the damage, advice must then be given.
Assessment of Damage
Plaster Insulation block Facing brick
Vinyl-asbestos tiles dpc
100 mm concrete
Concrete strip foundation
900 mm minimum from ground level
Cavity fill Hardcore fill
Damp-proof membrane (polythene)
FIG 3.9 Typical 1970 domestic foundation.
There are three possible situations with which the surveyor may have to deal. First, acting for an intending purchaser and in this circumstance the client will have the choice of either buying the property or not buying it. If the client decides to buy he or she will probably have to do so within a reasonably short space of time, therefore there will be no oppor-tunity for an extended period of observation. If there is any doubt about the signifi cance of structural damage, it is clearly better not to buy the property and to look elsewhere. If then having had all the possibilities explained to him or her the client still wishes to buy, it is suggested that some adjustment of the purchase price might be recommended having regard to (a) the maximum likely cost of remedying the most severe defect likely to exist, and (b) the probability that such a remedy may be required having regard to the results of whatever investigations the client is prepared to undertake prior to buying.
The second situation occurs when the surveyor is consulted by an owner who is wor-ried by signs of structural distress in his or her property. Advice given might then be (a) to do nothing, or (b) to subject the structure above ground to an extended period of observation using tell-tales and other indicators, or (c) in Categories 4 and 5 cases, to undertake temporary shoring and carry out trial excavations to determine the facts with a view to a subsequent specifi c remedy such as underpinning .
The third situation which can arise is where a building is inspected for a prospective mortgagee and signs of structural distress are found. In this situation the amount of
the mortgage advance proposed, in relation to the current market value, should be taken into account and a view expressed on the client’s behalf of structural repair costs which could arise in relation to the probability of such repairs being needed and to the percentage advance involved. In many cases of lower percentage advances it would be reasonable to make such an advance on the security of a building suff ering Categories 1, 2 or 3 damage. Categories 4 or 5 damage would require further investigation unless the mortgage advance was very low indeed. In addition to advising mortgagees in such circumstances the surveyor would be bound to bring such a situation to the attention of the borrower if he is to have a copy of the report, and the borrower should be advised to take further advice before proceeding, irrespective of the outcome of the mortgage application.
A further point worthy of note in connection with structural damage due to subsid-ence, landslip or ground heave (normal insured risks in many building insurance poli-cies) is that such a cover applies only to damage arising after the policy came into force.
It follows that an existing building owner may be covered for such risks in respect of damage apparent in his building but that if he sells, the purchaser may not be covered if signs of damage were apparent before the sale. Once a purchaser has commissioned a surveyor’s report which has described structural damage he may be placed in a dif-ferent position to recover subsequent costs under his insurance policy. In such a situ-ation it may be that the vendor could make a claim and agree the extent of remedial works required prior to any sale. A purchaser should not assume that, because he is FIG 3.10 London stock brickwork laid in lime mortar to English bond c.1900 and a signifi cant structural fracture which widens to about 75 mm. A crude linear telltale has been fi xed over the crack to measure movement. This telltale will indicate the extent of movement over time but it will not tell us which part of the wall is moving relative to the other part, or indeed whether both sections of the wall are moving. A rather more sophisticated method of measurement is needed to confi rm precisely what is going on.