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Survey finding

Cellar damp on your survey: what to do

Needs attention

UK cellars are nearly always damp. This page covers the difference between manageable and problem damp.

Last updated: 6 May 2026. Editorially reviewed: 20 May 2026.

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Finding

Cellar / basement damp

Needs attention

What this usually means

UK cellars are nearly always damp to some degree because they sit below water table or are surrounded by saturated ground. Whether it's a problem depends on use: storage cellars tolerate it; converted living spaces need tanking or cavity drain membrane systems.

Why it matters

Tanking failure or unaddressed damp in habitable cellar conversions is a category 3 finding that can affect both habitability and lender appetite.

Ask your surveyor

  • Check:Is the cellar in use as habitable space, and does it meet building regulations?
  • Check:What is the existing waterproofing system and is it functioning?

Ask the seller

  • Check:When was the waterproofing system installed and by whom?
  • Check:Is there a maintenance schedule for the pumps?

Next steps

  • •Get two written quotes from local trades before negotiating with the seller.
  • •Speak to your mortgage broker before exchanging if the finding affects mortgageability.
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Damp risk often tracks EPC band and building age. The full report checks both.

What you need to know

Severity

3/ 5

Significant. Specialist follow-up usually warranted before exchange.

Typical cost to fix

Cementitious tanking £100-£200/m². Cavity drain membrane (CDM) system with sump and pump £150-£300/m² (typical 30m² cellar £4,500-£9,000). Periodic pump and damp-proofing maintenance £200-£500/year.

Mortgage impact

Lender may exclude habitable use if damp is severe; usually lend on the rest of the property.

Insurance impact

Cellar contents are commonly excluded or limited.

When to pull out

Pull out only if cellar habitability was material to the purchase price.

When to renegotiate, and by how much

Cost of remediation if you intend habitable use; typical 1-3% off purchase price.

Thinking of pulling out or renegotiating? What to do after a bad survey

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How MyPropertyScan produces this guide, and what it is not

Published by MyPropertyScan and written by , who is accountable for its accuracy. No page here is written or reviewed by a chartered surveyor, conveyancer or regulated adviser, and we do not claim otherwise.

This page is not:

Figures and process steps come from the published UK datasets and standards listed on this page, not from professional practice. Pages are updated when source coverage, survey cost assumptions, or lender and legal requirements materially change. Dataset limitations are set out on the methodology page.

Spotted something out of date or wrong? Email hello@mypropertyscan.com and we will correct it and change the update date.

Sources used

We use UK public and specialist sources where they are available. Public datasets can be incomplete, delayed, or missing for some addresses. Treat them as a starting point, not as a replacement for professional advice.

Source standard: preference goes to official government datasets, statutory bodies, professional standards, and primary dataset publishers. We cite the source family on the page and explain coverage limits rather than filling gaps with unsupported estimates.

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