Glossary

The words on the survey, in plain English.

Name: Subsidence Ltd
Address: Unit 26, Winnington Business Park, Wolstencroft, Cheshire, CW8 4DL, GB
Telephone: 0333 1300 592
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If you've just read a structural engineer's report and felt like you'd skipped a chapter, this page is for you.

Close‑up of cracking plaster on an interior wall.

Glossary

The words on the survey, in plain English.

If you've just read a structural engineer's report and felt like you'd skipped a chapter, this page is for you.

Ground movement

4 terms

Subsidence: Downward movement of the ground beneath a structure after the building was completed. The classic UK driver is shrink/swell clay; tree roots, leaking drains and historic mining are the other common causes.
Settlement: Even, expected compaction of the ground beneath a new build in its first few years. Cosmetically annoying, structurally normal.
Heave: Upward movement of the ground beneath a footing — the opposite of subsidence. Often follows tree removal, as previously dehydrated clay rehydrates and swells back up.
Differential movement: Movement that affects one part of a structure more than another. Produces the diagonal, tapered cracks that are the textbook visual signal of subsidence.

Soil & ground

4 terms

Shrinkable clay: Clay soils whose volume changes significantly with moisture content. London clay is the highest‑profile UK example and the single biggest driver of seasonal subsidence claims.
Made ground: Ground that has been artificially placed or disturbed — fill, demolition rubble, infilled mine workings. Can be highly variable in bearing capacity.
Lias clay: A grey, mudstone‑rich clay common across the South West and Midlands. Less seasonally active than London clay but still subsidence‑prone.
Glacial till: Unsorted material left behind by glaciers — common across the North of England and Wales. Generally good bearing, but pockets of soft material can drive localised movement.

Repair methods

4 terms

Resin injection: Polyurethane rigid foam resin injection — a two‑part structural resin injected through 16mm tubes to re‑bear the soil column beneath an affected footing. Reaches load‑bearing strength in around fifteen minutes.
Underpinning: Excavating beneath an existing foundation and constructing a new, deeper foundation by hand. Effective but slow, intrusive and disruptive.
Mass concrete underpinning: The traditional underpinning method — pits dug in sequence along the perimeter, filled with poured concrete. Costly and dependent on cured concrete reaching strength.
Mini‑piling: An intermediate underpinning method using small steel‑cased piles driven to a load‑bearing stratum. Less disruptive than mass underpinning but still requires excavation.

Surveys & paperwork

4 terms

Laser baseline survey: A sub‑millimetre measurement of every external wall, used to establish whether movement is active and to monitor outcomes after treatment.
BRE category (0–5): The Building Research Establishment's six‑point scale for crack severity by width and effect. A standard reference across the UK construction industry.
Party Wall Act: 1996 Act that requires consent from neighbouring owners for works affecting a shared (party) wall. Resin injection generally does not trigger it because there's no excavation.
Section 20 consultation: The leasehold consultation required of freeholders / housing associations before significant works to a building. Our paperwork is supplied in a Section‑20‑ready format on request.

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