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.
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 building compressing the ground under its own weight in its first years (insurers generally treat movement within ten years of construction as settlement), and different again from a new build simply being outside construction tolerances. The test engineers apply is whether the ground would have moved even without the building on it; if so, it is subsidence. 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. Our guide to subsidence repair costs explains what each stage costs in 2026, and our guide to subsidence insurance claims explains what the policy covers and how a claim runs.
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.
These indicators suggest possible foundation-related movement. On their own they are not proof of subsidence, but together they justify a closer look.
Confirming the cause is the single most important step, it determines whether the problem can be removed, monitored or needs structural repair.
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. See our guide to trees and subsidence: prune, fell or underpin.
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 CCTV survey and water test; see our guide to leaking drains and subsidence.
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.
Nationally about 70% of subsidence is clay-related and roughly half of all cases involve a tree or large shrub, so those two cards cover most London claims. We also check for the less common causes: fine sand washing out near soakaways and downpipes, ground softening beside a neighbour's new basement or a deep drain trench, sulphate reactions lifting a ground floor slab, heave where clay swells after a tree has been removed, and the many things that mimic subsidence without involving the foundations at all, such as roof spread, failed lintels or wall ties, timber shrinkage and thermal movement. Houses built before about 1970 have rigid-jointed drains that leak readily, which is why a drain survey is part of almost every assessment.
A measured, evidence-led sequence so that any repair addresses the real cause rather than the symptom. For an example of this approach on site, see our structural remediation project in Epsom, where a cracked retaining wall capping beam was diagnosed and repaired.
A desktop study first: geology mapping, street imagery over the years to see what has grown or been removed, planning records for past alterations. Then an on-site structural inspection of every elevation, sketching each crack with its width and where it meets a corner or opening, with review of the building, ground conditions, drains and any nearby trees.
Read the crack pattern against the subsidence signature, sight along the brick courses for the dip, and identify the likely cause and whether movement is active, distinguishing subsidence from settlement, thermal or shrinkage cracking and from superstructure defects such as lintels, wall ties and roof spread.
Where movement may be ongoing, crack monitoring from fixed studs read with a digital calliper to 0.1 mm, and precise level monitoring along a brick course every six to eight weeks, typically for six to twelve months. Seasonal movement points to trees and clay; steady one-way movement points to drains or soft ground. See our guide to crack and level monitoring.
Where needed, our specialist site team digs trial pits beside the footing for the engineer to record its depth and bearing, extends them by hand auger to around 3 m, and takes samples for moisture and plasticity testing; a CCTV drain survey and water test confirm any leaks; roots are identified where trees are suspected.
Set out a clear strategy in the order current guidance requires: confirm the building is stable, deal with the ground (drain repair, crown reduction of the tree, moisture control), then repair the damage with crack stitching, repointing and making good. Foundation works only if movement continues.
Only where the evidence supports it, design the underpinning, usually partial, handle Building Regulations and any Party Wall notices, carry out or oversee the works, and issue a Certificate of Structural Adequacy with as-built drawings on completion.
Subsidence assessment sits alongside our wider survey and repair work. These pages cover the related services you may need.
Inspections and defect reports for buyers, owners, landlords and businesses.
Learn moreStructural versus non-structural crack diagnosis, stitching and repair strategy.
Learn moreUnderpinning assessment and design where foundations need stabilising.
Learn moreEngineering-led repair strategies, specifications and remediation.
Learn moreSubsidence is suggested by diagonal cracks that taper, wider at one end, starting at a corner of the building or the corner of a door or window, running through brickwork and plaster and often continuing below the damp-proof course, together with 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.
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.
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.
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.
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.
Typically six to twelve months, because a full summer and winter are needed to tell seasonal movement, which points to trees and clay, from progressive movement, which points to a leaking drain or soft ground. Crack widths are read from fixed studs with a digital calliper to a tenth of a millimetre, and level readings are taken along the brick courses every six to eight weeks. On an insurance claim the insurer normally funds the monitoring and it can run longer. Repairs are only specified once the readings show movement has stopped.
A written record that the cause was found and dealt with: the investigation report, the repair specification, the Building Regulations completion certificate where underpinning was carried out, the contractor's guarantee, and a Certificate of Structural Adequacy from the engineer confirming the cause, the works, the approvals and the inspections. Together these are what insurers, lenders and a future buyer's solicitor will ask to see.
At EMA Structures a subsidence assessment, covering the inspection, a record of every crack, a level survey along the brick courses, a diagnosis of the likely cause and a full written report, costs £495 to £895 plus VAT depending on the size of the property and the type of movement. Where monitoring is needed, installing the crack studs and level markers and taking three seasonal readings costs £1,200 to £2,000 plus VAT, with further visits at £350 plus VAT each. Trial pits and drain surveys are quoted separately, and on an accepted insurance claim the insurer normally funds the investigation and monitoring. Fees correct as of September 2026 and confirmed in writing before the visit. See our full fees guide.
Send us your photos and a short description, and we will advise whether a subsidence assessment is the right next step.
