Subsidence vs Settlement: How Surveyors Tell the Difference

In short: Settlement is the initial, usually harmless movement of a building as its foundations bed down under its own weight, and it normally stops within the first few years. Subsidence is ongoing downward movement caused by the ground beneath the foundations shrinking, softening or washing away. Subsidence can keep getting worse; settlement normally does not.

Last reviewed: 5 October 2026 by Patrick Oliver BSc (Hons) MRICS, RICS Registered Valuer.

Few words in a survey report worry a buyer more than "subsidence". In practice, most of the cracks I record on inspection are not subsidence at all. They are historic settlement, thermal movement or plaster shrinkage, and none of these threatens the structure. The skill lies in telling the two apart, because the answer affects the purchase, the mortgage, the insurance and the eventual resale value. This guide explains how I make that distinction on site.

What is the difference between subsidence and settlement?

Settlement and subsidence both involve a building moving downwards, but they have different causes and very different implications. Settlement is the building compressing the ground beneath it under its own weight. Subsidence is the ground itself moving away from beneath the foundations, independently of the weight of the building.

	Settlement	Subsidence
Cause	The weight of the building compressing the soil beneath it	Loss of support from the ground: clay shrinkage, tree roots, leaking drains, mining or soft ground
When it happens	Mostly in the first few years after construction or an extension	At any point in a building's life, often after a hot, dry summer
Progression	Stabilises and stops	Can be ongoing, seasonal or accelerating
Typical cracking	Fine, old cracks, often filled or decorated over	Cracks that are fresh, widening, tapered and often reappear after filling
Insurance	Generally excluded from buildings policies	Generally covered under standard buildings policies, subject to a higher excess

What causes subsidence?

Subsidence is usually caused by a change in the moisture content of the soil beneath the foundations. The most common causes I see are:

• Shrinkable clay soils. Clay shrinks as it dries and swells as it gets wet. London Clay, which underlies much of London and parts of the South East, is particularly prone to this, which is why claims rise sharply after hot, dry summers.
• Trees and large shrubs. Roots draw moisture out of clay soils, sometimes at a considerable distance from the tree. Species such as oak, willow and poplar are the usual suspects, although the soil type matters as much as the species.
• Leaking drains and water mains. On sandy or granular soils, escaping water can wash fine particles away from under the foundations. On clay, it can soften the ground so that it loses its bearing capacity.
• Mining and made ground. Former coal workings remain a consideration in parts of Yorkshire. Infilled pits, quarries and poorly compacted made ground can also cause movement elsewhere.

Two related movements are worth knowing about. Heave is the opposite of subsidence: the ground swells and pushes upwards, often after a large tree has been removed from clay soil. Landslip is the downhill movement of the ground on a slope. Standard buildings policies usually cover subsidence, heave and landslip together.

Is settlement something to worry about?

Settlement is rarely a structural concern once it has stopped. Almost every building settles slightly when it is new. Older houses with shallow foundations often show distortion from movement that happened many decades ago. Sloping floors, out-of-square door frames and old, filled cracks are common in Victorian and Edwardian housing. On their own they do not suggest a current problem.

Settlement does deserve closer attention in one situation: a recent extension. A new extension built on deeper foundations than the original house can settle at a different rate. The result is a crack where the old and new structures meet. That crack is usually a consequence of the junction detail rather than subsidence, but it needs to be distinguished properly.

How do surveyors tell subsidence from settlement?

Surveyors tell subsidence from settlement by reading the pattern, age and behaviour of the cracking together with the site conditions, not by looking at any single crack in isolation. On site, I am looking at:

• Crack shape. Subsidence cracks are typically tapered: wider at one end than the other, often running diagonally through brickwork and around door and window openings. Uniform hairline cracks are more often shrinkage or thermal movement.
• Freshness. Clean, sharp crack edges with no dirt, paint or cobwebs suggest recent movement. Old cracks that have been painted over and have not reopened point towards historic movement.
• Visibility inside and out. A crack that passes right through the wall and can be seen on both faces is more significant than one confined to internal plaster.
• Distortion of openings. Doors and windows that have recently started sticking, or gaps opening above door frames, suggest that the structure is still moving.
• The site. Nearby trees, the likely soil type, the age and depth of the foundations, the condition of the drains and any history of claims in the street all inform the diagnosis.

Where the evidence is not conclusive, the honest answer is that a single inspection cannot settle the question. Monitoring is the next step.

How serious is a crack in my wall?

The severity of a crack is usually graded using the classification in BRE Digest 251. That scale runs from Category 0 (negligible) to Category 5 (very severe), based mainly on crack width and how easily the damage can be repaired.

BRE category	Approximate crack width	Description	Typical implication
0	Up to 0.1mm	Negligible	Aesthetic: redecoration only
1	Up to 1mm	Very slight	Aesthetic: redecoration only
2	Up to 5mm	Slight	Aesthetic: filling and redecoration, possibly some repointing
3	5mm to 15mm	Moderate	Serviceability: opening up and repair, doors and windows may stick
4	15mm to 25mm	Severe	Serviceability: extensive repair, sections of wall may need rebuilding
5	Over 25mm	Very severe	Stability: major structural repair, possibly partial rebuilding

Width is only part of the picture. A 2mm crack that is widening each month tells me more than a stable 6mm crack that has not moved in thirty years. BRE itself stresses that whether cracks are increasing over time affects the classification.

What happens if subsidence is suspected?

If subsidence is suspected, the cause and whether the movement is ongoing need to be established before any repair is designed. The usual sequence is:

1. Notify the buildings insurer as soon as subsidence is suspected, if you own the property. Insurers usually appoint their own loss adjuster or engineer to investigate.
2. Investigation. This typically involves trial pits to expose the foundations, boreholes to identify the soil, root sampling where trees are suspected, and a CCTV survey of the drains.
3. Monitoring. Crack-width gauges or level monitoring, often over a period of up to a year, to show whether movement is seasonal, progressive or has stopped.
4. Remove the cause. This usually means repairing the drains or managing or removing the vegetation responsible. In many cases this is enough to stabilise the building.
5. Repair. Once the building is stable, cracks are repaired, often with helical bar reinforcement and repointing, and the property is redecorated. Underpinning is reserved for cases where the cause cannot be removed or movement continues, and is needed far less often than many people assume.

Does subsidence affect the value of a property?

Subsidence affects value mainly through its effect on insurability and buyer confidence, rather than through the repair cost alone. In my experience as a valuer, the market discount depends on three things. First, whether the movement is current or historic. Second, whether repairs have been completed and signed off with a certificate of structural adequacy. Third, whether the property can be insured on normal terms.

A property with a historic, fully repaired and certified subsidence claim, and buildings insurance in place, will usually sell close to its unaffected value. A property with ongoing, undiagnosed movement is a different matter. Lenders may retain part of the mortgage advance or decline to lend until the position is clear, and the pool of buyers shrinks accordingly. Buyers should ask the seller whether the existing insurer will continue cover, because changing insurer after a subsidence claim can be difficult.

Common mistakes I see

• Assuming every crack is subsidence. Most cracks in older houses are historic, cosmetic or caused by thermal and shrinkage movement. Treating them all as subsidence can derail a perfectly sound purchase.
• Assuming no crack means no risk. A freshly redecorated wall can hide recent movement. I look at the site conditions, not just the finishes.
• Removing a mature tree without advice. On clay soil, removing a large, established tree can trigger heave as the ground rehydrates. Take advice from an engineer or arboriculturist first.
• Jumping straight to underpinning. Underpinning is expensive and disruptive, and it is often unnecessary once the cause has been dealt with.
• Not checking the paperwork. When buying a property with past movement, ask for the insurer's claim file, the engineer's reports and the certificate of structural adequacy. The absence of these documents is itself a warning sign.

How AJA Surveyors can help

Assessing structural movement is a routine part of every RICS Building Survey and HomeBuyer Report I carry out across South London, Surrey and Yorkshire. Where cracking needs a more focused look, a General Structural Inspection will tell you whether the movement is historic or current, what is likely to have caused it, and what should happen next. If you are unsure which level of survey you need, my guide to Building Surveys vs HomeBuyer Reports explains the difference. It is also worth checking that your buildings sum insured is realistic: see why your buildings insurance sum could be wildly wrong. If you are concerned about cracking in a property you own or are buying, please get in touch.

Subsidence vs settlement: frequently asked questions

Is settlement the same as subsidence?

No. Settlement is the building compressing the ground under its own weight, usually in its early years, and it normally stops. Subsidence is the ground beneath the foundations losing support through shrinkage, softening or erosion, and it can continue or worsen over time.

Does buildings insurance cover subsidence?

Standard buildings insurance policies generally cover subsidence, heave and landslip, usually with a higher excess than other claims, typically around £1,000. Settlement, and damage to new structures bedding down, is usually excluded, so check the wording of your own policy.

What do subsidence cracks look like?

Subsidence cracks are typically tapered, wider at one end than the other, and often run diagonally through brickwork near doors and windows. They are usually visible inside and out, have clean, fresh edges and tend to reopen after being filled.

Should I buy a house that has had subsidence?

A house with historic, fully repaired subsidence can be a sound purchase if the insurer's file, engineer's reports and a certificate of structural adequacy are available and insurance continues on normal terms. Ongoing, undiagnosed movement is a much greater risk and should be investigated before you commit.

Does subsidence always need underpinning?

No. Most subsidence is stabilised by dealing with the cause, such as repairing leaking drains or managing nearby trees, followed by crack repair. Underpinning is generally reserved for cases where the cause cannot be removed or monitoring shows movement continuing.

If you are buying, I can quote for a RICS Level 2 HomeBuyer Report or a RICS Level 3 Building Survey in under a minute through our instant quote.

Patrick Oliver BSc (Hons) MRICS, Chartered Surveyor and RICS Registered Valuer, Aston James Associates

This article is general guidance on structural movement in residential properties and does not constitute a substitute for a professional inspection or a structural engineer's investigation. Every property should be assessed on its own facts.