Subsidence investigation and diagnosis
Subsidence is downward movement of the ground under a foundation, and the fix depends entirely on the cause. We investigate to establish that cause before anyone talks about underpinning, for owners and insurers across the UK.
How do I know if it is subsidence or just normal cracking?
You often cannot tell from the crack alone. Subsidence tends to produce diagonal cracks wider at the top, near openings, with sticking doors. But thermal movement and shrinkage look similar, so we assess the whole pattern, the history and the ground before concluding.
What subsidence is and what it is not
Subsidence is the downward movement of the ground supporting a building's foundations, usually because the soil has lost volume or strength. It is often confused with settlement, which is the normal bedding down of a new building, and with heave, which is upward movement when clay swells. The distinction matters because the crack patterns look similar to an untrained eye but the causes and cures are opposite. Diagnosing which one you have is the first job, and getting it wrong is expensive.
The classic signs are diagonal cracks that are wider at the top than the bottom, often near openings, doors and windows that begin to stick, and rippling in wallpaper along the line of movement. But cracks alone prove very little. Thermal movement, shrinkage of new plaster, sulphate attack and simple age all produce cracks too, so we look at the whole pattern and its history rather than reacting to a single line on a wall.
Investigating the cause
Most subsidence in the UK is clay related. Shrinkable clay soils lose moisture in dry summers and near thirsty trees, the ground shrinks, and the foundation drops with it. The other common causes are leaking drains washing fines out of the soil, made ground consolidating, and, in some regions, dissolution features or old mine workings. Each leaves a different signature, so we work through them methodically rather than assuming trees every time.
The investigation typically combines a soil assessment with trial pits to expose the foundation and the ground beneath it, a drainage survey where a leak is suspected, and a root and tree survey where vegetation is in range. Laboratory testing of the soil tells us its plasticity and moisture condition. Only once we understand why the ground is moving can we say whether the answer is managing vegetation, repairing a drain, or a structural repair to the foundation.
Monitoring, reporting and remedy
Because clay-related subsidence is seasonal, a single visit often cannot tell you whether movement is still active. We install monitoring, level datums or crack gauges read over a period that spans the seasons, to see whether the building is still moving and by how much. This evidence is what an insurer needs before authorising works, and it frequently shows that the cheapest remedy, removing or managing a tree and letting the ground recover, is enough.
Where movement is genuinely progressive and structural repair is justified, we set out the options, which may run from foundation strengthening to full underpinning. We report the cause, the evidence and the recommended remedy in a form insurers and loss adjusters accept, and we coordinate with them through the claim. This work is carried out across the UK, with desktop diagnosis and reporting available to European clients alongside a local site visit.
What we check.
The points our calculations resolve for a project like this.
- Distinguishing subsidence from settlement, heave and thermal cracking
- Identifying the actual cause: clay shrinkage, trees, drains, made ground or mining
- Trial pits to expose the foundation and the supporting ground
- Drainage and root surveys where a leak or vegetation is in range
- Seasonal monitoring to confirm whether movement is still active
- Reporting in a form insurers and loss adjusters accept
From enquiry to sign-off.
Enquiry
Send drawings or describe the problem. We confirm the scope, the deliverables and a target timescale.
Information
We agree the survey, drawings or data we need and any site access required.
Engineering
Design, calculation or assessment to the relevant Eurocodes and UK National Annex.
Issue
A clear, defensible report or set of calculations, with assumptions and limitations stated.
Common questions
How do I know if it is subsidence or just normal cracking?
You often cannot tell from the crack alone. Subsidence tends to produce diagonal cracks wider at the top, near openings, with sticking doors. But thermal movement and shrinkage look similar, so we assess the whole pattern, the history and the ground before concluding.
Do I need underpinning?
Usually not. Most subsidence is caused by clay shrinkage near trees or by a leaking drain, and removing the cause and letting the ground recover is enough. Underpinning is a last resort for genuinely progressive movement, confirmed by monitoring, not a default fix.
Why do you need to monitor before deciding?
Clay-related subsidence is seasonal, so a single visit cannot tell you whether the ground is still moving. Monitoring over a period that spans wet and dry seasons shows whether movement is active, which usually avoids unnecessary and costly works.
Will you deal with my insurer?
Yes. We establish cause against the evidence, provide monitoring and drainage findings, and report in a form loss adjusters accept, and we coordinate with them through the claim so the diagnosis and any works are agreed.
What does a subsidence investigation cost?
It starts for the initial investigation and report. Trial pits, soil testing, drainage surveys and a period of monitoring are additional and depend on what the diagnosis needs, agreed with you before we proceed.
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Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
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