Clay shrinkage & trees
Shrinkable clay soils, common across much of London, shrink as they dry out. Tree and shrub roots draw moisture from the soil, causing it to contract and the foundations above to drop, particularly in long, dry summers.
Subsidence & Movement
Subsidence Survey & Structural Movement Assessment London
Engineer-led assessment of subsidence and structural movement across London, inspection, crack and movement diagnosis, monitoring advice, intrusive investigation, a clear repair strategy and underpinning only if required.
The Short Answer
What is subsidence?
Subsidence is the downward movement of the ground beneath a building's foundations, causing the structure above to drop and crack. It is different from settlement, which is the small, expected movement of a new building as it beds in. Subsidence matters when it is progressive, when the ground continues to move and the foundations are no longer fully supported. Common triggers in London include shrinkable clay soils drying out around tree roots, water escaping from leaking drains, and poorly compacted made-up ground. A proper assessment confirms whether movement is active, identifies the cause, and sets out what, if anything, needs to be done.
Not every crack means subsidence. The purpose of an engineer-led assessment is to separate normal settlement, thermal movement and shrinkage from genuine foundation-related defects, so you can act with confidence rather than worry. Where this comes up while selling a property, a pre-sale structural review can address it before it reaches a buyer's surveyor.
Warning Signs
Signs of subsidence to look for
These indicators suggest possible foundation-related movement. On their own they are not proof of subsidence, but together they justify a closer look.
- Diagonal cracks that are wider at the top than the bottom
- Cracks appearing near doors, windows and other openings
- Cracks wider than around 3mm running through brickwork and plaster
- Doors and windows that begin to stick or no longer close cleanly
- Cracks visible both inside and outside in the same location
- Rippling or tearing wallpaper at wall and ceiling junctions
- Sloping or uneven floors and skirting boards pulling away
- Gaps opening between extensions, bay windows and the main building
- Nearby mature trees, hedges or recently removed vegetation
- Cracks that are widening or changing over weeks and months
Root Causes
Common causes of subsidence
Confirming the cause is the single most important step, it determines whether the problem can be removed, monitored or needs structural repair.
Drainage leaks
Water escaping from cracked or leaking drains and pipes can wash away or soften the soil supporting the foundations. Leaks are a frequent cause and are usually confirmed with a drainage survey.
Made-up ground
Where a building sits on poorly compacted fill, demolition rubble or made-up ground, the soil can consolidate or wash out over time, leaving the foundations unevenly supported.
Our Process
From inspection to confirmed repair strategy
A measured, evidence-led sequence so that any repair addresses the real cause rather than the symptom.
1
Inspect
On-site structural inspection of cracking, movement and external indicators, with review of the building, ground conditions and any nearby trees.
2
Diagnose
Identify the likely cause and assess whether movement is active, distinguishing subsidence from settlement, thermal or shrinkage cracking.
3
Monitor
Where movement may be ongoing, recommend crack monitoring over a period to establish whether it is progressive or stable.
4
Investigate
Where needed, intrusive investigation such as trial pits, soil sampling and a drainage survey to confirm foundation depth, soil type and any leaks.
5
Repair strategy
Set out a clear repair strategy and specification, from removing the cause and crack stitching to foundation works.
6
Underpinning if required
Only where the evidence supports it, design underpinning and foundation stabilisation, with contractor coordination and review.
Related Services
Where subsidence assessment fits
Subsidence assessment sits alongside our wider survey and repair work. These pages cover the related services you may need.
Structural Survey London
Inspections and defect reports for buyers, owners, landlords and businesses.
Learn moreCrack Repairs London
Structural versus non-structural crack diagnosis, stitching and repair strategy.
Learn moreUnderpinning London
Underpinning assessment and design where foundations need stabilising.
Learn moreStructural Repairs London
Engineering-led repair strategies, specifications and remediation.
Learn moreFAQs
Subsidence questions, answered
How do I know if my house has subsidence?
Subsidence is suggested by diagonal cracks that are wider at the top than the bottom, cracks near doors and windows, doors and windows that begin to stick, and rippling wallpaper at wall and ceiling junctions. Not all cracks indicate subsidence, so an engineer-led inspection is needed to distinguish active structural movement from harmless settlement or thermal cracking.
Is subsidence always serious?
No. Many cracks are caused by minor settlement, thermal movement or shrinkage and are not structurally significant. Subsidence becomes serious when movement is progressive and affects the foundations. The purpose of an assessment is to confirm whether movement is active, identify the cause and decide whether monitoring or repair is required.
Do I need underpinning?
Underpinning is only one of several possible outcomes and is not always necessary. Where the cause can be removed, for example a leaking drain or vegetation, stabilisation may follow without underpinning. Underpinning is considered when foundations have been undermined and movement cannot otherwise be halted. We recommend it only when the evidence supports it.
Should I tell my insurer?
Subsidence is usually covered by buildings insurance, and most policies require you to notify your insurer once subsidence is suspected. We can provide a clear structural assessment to support your claim and help you understand the cause and likely repair strategy before works begin.
How is the cause of subsidence confirmed?
The cause is confirmed by combining a visual inspection with monitoring of crack movement over time and, where needed, intrusive investigation such as trial pits to expose the foundations, soil sampling and a drainage survey. This evidence identifies whether clay shrinkage, drainage leaks, trees or made-up ground are responsible before a repair strategy is set.
Worried about cracks or movement in your property?
Send us your photos and a short description, and we will advise whether a subsidence assessment is the right next step.