Subsidence Survey

No — and this is one of the most important distinctions our survey makes. Many cracks in buildings are entirely benign and result from normal thermal expansion and contraction, plaster shrinkage, or minor settlement that occurred shortly after construction and has long since ceased. Hairline cracks (less than 1 mm wide) in plasterwork that have not changed in years are rarely a cause for concern. Subsidence cracks, by contrast, tend to be wider (typically 2 mm or more), tapered (wider at one end than the other), diagonal or stepped (following mortar joints in brickwork), and are often accompanied by other signs of movement such as sticking doors, sloping floors or gaps at skirting boards. The presence of cracking on both the internal and external leaf of a cavity wall at the same location is also a strong indicator of structural movement. Our survey distinguishes between the two and gives you an evidence-based answer — not guesswork.

Subsidence is the downward movement of the ground beneath a building caused by factors external to the building — such as clay shrinkage, tree root moisture extraction or soil washout from a leaking drain. Settlement is downward movement caused by the weight of the building itself compressing the soil beneath the foundations; it is normal and expected to some degree in all new buildings, usually within the first few years after construction. Heave is the opposite of subsidence — upward movement of the ground, typically caused by clay soils swelling as they rehydrate after a tree has been removed or a prolonged dry period has ended. Each mechanism produces a different pattern of cracking, and the correct diagnosis is essential because the remediation for subsidence (underpinning, tree management, drain repair) is different from the remediation for heave (which may require compressible void formers and flexible service connections).

Our subsidence survey starts from £350 plus VAT for a typical residential property. The exact price depends on the size of the property, the complexity of the cracking, whether CCTV drainage inspection is required and the number of trees within the zone of influence. We provide a fixed-price quote within 24 hours of your enquiry — the price we quote is the price you pay, with no hidden extras, no travel surcharges and no additional fees for any location within our seven counties (Bedfordshire, Buckinghamshire, Cambridgeshire, Hertfordshire, Northamptonshire, Greater London and Oxfordshire). We are entirely independent — we do not undertake underpinning or structural repair works and have no financial interest in any remediation contractor — so our advice is always impartial.

Most UK buildings insurance policies cover subsidence, but the excess is typically significantly higher for subsidence claims — often £1,000 or more — and making a claim can affect your future premiums and the insurability of the property. Insurance companies will usually require a professional subsidence investigation report before they will process a claim, and our survey is designed to meet the requirements of UK insurers. However, we do not deal directly with insurance companies — the survey is commissioned by you, the homeowner or buyer, and you provide the report to your insurer as part of your claim. If the survey confirms subsidence that is covered by your policy, the cost of the survey may itself be recoverable as part of your claim. We recommend checking your policy wording before commissioning a survey.

A subsidence survey typically takes between 1.5 and 3 hours on site, depending on the size of the property, the extent of cracking and the complexity of the investigation. A straightforward case with localised cracking on a modern property may take 1.5 hours; a complex case involving a large period property with cracking in multiple locations, significant tree influence and drainage investigation may take up to 3 hours. The surveyor will inspect every accessible room internally, the full external envelope, the foundations where visible, all trees and large shrubs within influencing distance, and the drainage system where access permits. You are welcome to be present during the inspection — the surveyor can explain findings as they go and answer your questions on the spot.

In many cases, yes. The appearance of the crack edges — whether they are sharp and clean (recent movement) or dull, dust-filled and painted over (historic, stable movement) — is one indicator. The presence of previous crack repairs that have themselves cracked is strong evidence of ongoing movement. We also install tell-tale crack monitors across representative cracks; these are simple graduated gauges that show whether a crack is widening, closing or stable when re-inspected after a period of weeks or months. In some cases, we may recommend a period of crack monitoring before making a definitive diagnosis, particularly if the cracking could be seasonal (clay shrink-swell) and the inspection takes place during a period of normal rainfall. We cover all seven of our counties: Bedfordshire, Buckinghamshire, Cambridgeshire, Hertfordshire, Northamptonshire, Greater London and Oxfordshire.