Foundation Cracks near you

Shrinkable clay underlies a great deal of England, and clay gives up water in a dry spell and takes it back in a wet one. A foundation sitting in that clay rides the movement, and a wall above it opens and closes a crack on an annual cycle. That is why Approved Document A ties foundation depth on clay to vegetation as well as soil: strip foundations should be taken to a depth where anticipated ground movements will not impair stability, with due consideration of the influence of vegetation and trees, and with minimum depths on clay of 0.75m, 0.9m and 1.0m for low, medium and high shrinkage clay soils respectively, increased where there are trees nearby.

Older houses were often built shallower than any of those figures, which is not a defect in a building that has stood for a century but does explain why a drought year produces a crop of new cracks in Victorian and Edwardian streets and few in the modern estate next door. It also explains why the same crack can look alarming in September and unremarkable the following April.

Not every crack is ground movement at all. Thermal expansion of a long wall, a deflecting lintel over an opening, corroding wall ties, sulphate attack on render, shrinkage in a new extension and simple plaster movement all produce convincing cracks. A diagnosis that jumps straight to subsidence without considering these is not a diagnosis.

The point of monitoring is to separate movement that has finished from movement that is continuing, and seasonal movement from progressive movement. That means readings taken at intervals over a period long enough to include both a dry and a wet season, recorded consistently, rather than an opinion formed on a single visit. Alongside it, an investigation should look at the drains near the affected corner, the trees and vegetation within influencing distance, the depth and condition of the footing and the soil it sits on.

GOV.UK's land stability guidance expects assessment of ground instability to be prepared by an appropriately qualified person, such as a chartered member of a relevant professional institution. For a house, that normally means a structural engineer, and it is worth being clear whether the person writing your report is one, and whether they have any interest in the repair that follows.

When you are ready for quotations, LokalMatch puts one description of the job in front of several firms: say what the cracking looks like, when you first noticed it, what any monitoring or engineer's report concluded, and give your postcode, and contractors covering your area get in touch. They pay for the requests they receive, homeowners do not. LokalMatch neither carries out repairs nor sets prices, and does not vet, rank or recommend any contractor, so comparing what each quotation actually includes, and on what diagnosis it rests, remains with you.

Filling and redecorating is the right end of the job, not the whole of it. Where movement has genuinely stopped, and where the cause has been identified and dealt with, making good the crack is ordinary building work and there is no reason to do anything more elaborate. Where movement is continuing, the filler simply cracks again and the money is gone.

The sequence that works is cause, then stability, then repair, then decoration. If a leaking drain was washing out the ground, the drain is repaired first. If vegetation was drying the clay, that is dealt with on engineering advice. If the footing itself is inadequate and the building is genuinely bearing badly, structural work is designed by an engineer, and that work is building work in its own right where it involves underpinning.

Be wary of two shortcuts. One is a repair specified before any monitoring has been done, which is a guess with a price attached. The other is a cosmetic repair sold as a structural cure, which can matter later: a buyer's surveyor is likely to ask what caused the cracking and what was done about it, and a filled crack with no explanation behind it invites exactly the questions you would rather have answered in advance.

Ordinary making-good of your own wall is not usually a notifiable event, but two thresholds are worth knowing. Underpinning a building is building work under regulation 3(1)(f) of the Building Regulations 2010, so where a crack repair turns into foundation work it engages building control, and approval comes from a building control body, either the local authority's building control department or a private registered building control approver.

The second threshold is the party wall. In England and Wales, section 2(2) of the Party Wall etc. Act 1996 gives a building owner the right to make good, repair, or demolish and rebuild, a party structure or party fence wall in a case where such work is necessary on account of defect or want of repair, and to underpin, thicken or raise a party structure. Exercising those rights requires a party structure notice under section 3, served at least two months before the date on which the proposed work will begin.

If the repair involves excavating near the neighbour's building, section 6 applies as well, with its three metre and six metre tests and at least one month's notice before excavation begins. GOV.UK's explanatory booklet is clear that the Act is separate from planning or building regulations control, so a building owner with approval under one still has to follow the procedures under the other.

Most cracking in British houses is slow, seasonal and undramatic. A small number of situations are not, and they deserve a different response: cracking that appears suddenly and widens over days, a wall that is visibly bulging or leaning, a lintel or beam that has dropped, cracking that follows an impact, a fire, an escape of water or nearby excavation, or any crack accompanied by floors moving underfoot.

In those cases stop work that might be making it worse, keep people away from the affected area, and get a structural engineer to look at it quickly. Your local authority's building control department is also the right place to raise a building that appears to be in a dangerous condition. Excavation nearby is worth taking seriously in its own right: HSE warns that no ground can be relied upon to stand unsupported in all circumstances, and that excavations should not undermine the foundations of nearby buildings or walls, noting that many garden or boundary walls have very shallow foundations which are easily undermined by even small trenches.

Take dated photographs with something for scale before anything is disturbed, and keep them. Whether the matter ends with an engineer, a contractor or an insurer, a clear record of what the crack looked like and when is the single most useful thing a homeowner can produce.