Guide
Subsidence investigation and monitoring: the sequence and what it costs
Updated
Subsidence work follows a sequence, and the sequence is why it takes months. Each stage exists to rule something in or out before anyone spends money on repairs.
The usual sequence
- Notification. If you have buildings insurance, you tell the insurer. In most cases they appoint the investigating engineer or loss adjuster, and the investigation runs through the claim subject to the policy excess.
- Initial inspection. A structural engineer inspects, records the cracking and forms a view on whether the pattern is consistent with ground movement. See engineer report costs.
- Monitoring. Fixed reference points are installed and read repeatedly, normally across a full seasonal cycle, so that seasonal clay movement can be distinguished from progressive movement.
- Targeted investigation. Depending on the working theory: a CCTV drainage survey, trial pits to expose the foundation, soil sampling and laboratory testing, and identification of any roots recovered.
- Repair scheme, if one is needed. Often the answer is removing or managing vegetation, or repairing a drain, followed by making good. Underpinning is one option among several and is not the default outcome.
Why monitoring takes months
Shrinkable clay soils swell in wet months and shrink in dry ones, so a building on clay can move seasonally and come back. A monitoring period that only covers a few weeks cannot tell you whether what it recorded is that annual cycle or a one-way trend. That is why monitoring is normally read at intervals across a full seasonal cycle before anyone commits to a repair scheme. It is slow by design, and a scheme specified without it is a scheme specified on a guess.
What each stage adds to the bill
| Stage | Main cost driver |
|---|---|
| Structural engineer inspection and report | Engineer time on site and in writing, plus travel; a fixed fee is normal for a standard house |
| Level or crack monitoring | Number of readings, the interval between them, and whether the closing interpretation report is included |
| CCTV drainage survey | Length of drain run surveyed, access, and whether jetting is needed before anything is visible |
| Trial pits and soil testing | Number and depth of pits, spoil handling and reinstatement, plus laboratory fees for soil classification |
| Root identification and arboricultural input | Laboratory identification fees plus an arboricultural opinion on which vegetation is implicated |
| Repair scheme design and supervision | Complexity of the scheme and the number of site inspections during the works |
Underpinning is a last resort, not step one
Underpinning deepens or strengthens the existing foundation, and it is expensive, disruptive and permanent. It is appropriate for some cases and unnecessary for many, because removing the cause, most often vegetation or a leaking drain, allows the ground to recover and the building to stabilise. Underpinning is structural building work, and the Building Regulations 2010 cover the construction and alteration of buildings; gov.uk advises checking with a building control body if you cannot decide whether your project needs approval (gov.uk). Any contractor proposing underpinning before monitoring and investigation have been done is proposing a solution to a problem nobody has diagnosed yet.
If your insurer is handling the claim, the investigation route and who pays for what are set by your policy and by the insurer. This page describes the technical sequence only. It is not insurance advice, and if you are unhappy with how a claim is handled, the Financial Ombudsman Service handles insurance complaints.