Subsidence in London: Signs, Causes & Repair Cost (2026)

Key Takeaways

Subsidence repair costs £5,000 to £15,000 on average, averaging around £12,500 (Checkatrade / MyJobQuote, 2026).
London's clay soils, nearby trees and leaking drains are common causes.
Underpinning methods: mass concrete (~£13k for a terrace), piling (~£23k), resin (~£11k).
Subsidence is usually covered by buildings insurance, with around a £1,000 excess.
Diagonal cracks wider than 5mm and sticking doors are warning signs.

Subsidence sounds alarming, but it is usually insurable and fixable. This guide explains the signs, the causes common in London, the repair methods and costs, and what to do if you suspect it.

How much does subsidence cost to fix?

Subsidence repair costs £5,000 to £15,000 on average, averaging around £12,500, with severe cases reaching much more, according to Checkatrade and MyJobQuote. It is usually covered by buildings insurance, with around a £1,000 excess.

Underpinning method (3-bed terrace)	Typical cost
Resin injection	around £11,000
Mass concrete	around £13,000
Piling	around £23,000

Source: Checkatrade, MyJobQuote and Mainmark, 2025 to 2026.

Causes in London

London's shrinkable clay soils are the main culprit, swelling and shrinking with moisture, especially in hot, dry summers. Nearby trees drawing water, and leaking drains washing away ground, are also common.

The signs

Watch for new diagonal cracks wider than 5mm, often near windows and doors and wider at the top, sticking doors and windows, and cracks visible inside and out in the same place. See our guide to cracks in walls and when to worry. Not all cracks mean subsidence.

What to do

If you suspect subsidence, contact your insurer, who usually arranges investigation and repair. GS Renovation carries out structural repairs and works alongside engineers across London. For advice, contact us or call 07472 424 226.

The GS Renovation Team

GS Renovation & Home Improvements has delivered kitchen, bathroom, structural and extension projects across London for over 30 years. This guide reflects current UK industry pricing and our hands-on site experience.

Frequently Asked Questions

How much does it cost to fix subsidence?

Fixing subsidence costs £5,000 to £15,000 on average in the UK, averaging around £12,500, though severe cases can reach £50,000. For a three-bed terrace, mass concrete underpinning costs around £13,000, piling around £23,000 and resin injection around £11,000. Most subsidence is covered by buildings insurance, typically with around a £1,000 excess.

What causes subsidence in London?

Subsidence happens when the ground beneath the foundations moves down. In London the most common causes are shrinkable clay soils that swell and shrink with moisture, trees and large shrubs drawing water from the soil, and leaking drains or water mains washing away ground. Hot, dry summers can trigger clay-related subsidence in vulnerable homes.

What are the signs of subsidence?

The classic signs are new, diagonal cracks wider than about 5mm, often near windows and doors and wider at the top, doors and windows sticking, rippling wallpaper, and cracks visible inside and outside in the same place. Cracks that appear suddenly or grow are more concerning than long-standing hairline cracks. A professional assessment confirms the cause.

Is subsidence covered by insurance?

Yes, in most cases subsidence is covered by buildings insurance, usually with a higher excess of around £1,000. If you suspect subsidence, contact your insurer, who will typically arrange investigation and any repair. Be aware that a history of subsidence can affect future insurance and the sale of the property, so it must be documented and resolved properly.

What is underpinning?

Underpinning strengthens and stabilises foundations that have moved, by extending them down to firmer ground or reinforcing them. Methods include mass concrete (digging out and filling beneath the footings), piling (driving piles to deeper strata), and resin injection (injecting expanding resin to stabilise the soil). The right method depends on the soil, the building and the cause.

Should I worry about buying a house with subsidence?

Not necessarily. Many homes with historic subsidence have been properly repaired and are perfectly sound, but you should get a full structural survey, see evidence of past repairs and monitoring, and check the insurance position, as a subsidence history can affect cover and price. Active, unresolved subsidence is a more serious concern that needs investigation.

Subsidence in London