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Buying in London: when to get a damp survey

London purchases come with particular damp risks: lower ground flats, converted houses where the structure is shared, basements with drainage systems, and period buildings in conservation areas. A homebuyer or building survey often flags damp and suggests a specialist. This guide explains when an independent damp survey is worth commissioning and how to use it.

Request a survey Fixed-price surveys from £215, report included

When it is worth it

In each case, the risk is either that the damp is more serious than it looks, or that you are about to be sold a remedy for something that does not need it.

  • Your survey or valuation recommends a damp or timber specialist
  • You are buying a lower ground or basement flat
  • The property has a basement with a drainage system and pump
  • You can see staining, mould or blown plaster on viewing
  • The seller has had damp proofing done and is offering a guarantee
  • The building is listed or in a conservation area

What it adds for a flat

For a flat, the key questions are where the water comes from and who is responsible for fixing it. The report records whether the damp starts within the flat or in the structure, roof, external walls or shared services, which matters for the lease, the service charge and any repair the freeholder may need to carry out. Your solicitor can raise that with the seller and the managing agent before exchange.

Basements

A basement with a drained membrane system needs its channels, sump and pumps serviced. The survey checks the condition of what can be seen, looks for evidence of past water entry, and lists the servicing records and guarantees to ask the seller for. That is information a buyer needs and seldom gets.

Using the report

The report arrives within 24 hours of the visit. It can support a price renegotiation, a request for specific works before completion, a retention, or enquiries through your solicitor to the freeholder. It can also give you confidence to proceed when the damp flagged by a general survey turns out to be minor.

ATi carries out no remedial work, so we have no interest in what the report concludes. That independence is what makes it useful to a buyer, a lender and a seller alike.

Questions

How fast can you survey before exchange?

We reply the same day, usually visit within a few days, and the report follows within 24 hours of the visit.

Do I need access to communal areas?

It helps. We arrange it through the agent where possible, and the report notes anything that could not be inspected.

Is a damp proofing guarantee from the seller worth anything?

Only if the treatment addressed the actual cause, the guarantee is transferable and someone still stands behind it. The survey can tell you whether the treatment matched the problem.

Can my solicitor use your report?

Yes. It is written so that a solicitor can raise specific enquiries from it.

Do you survey new build flats?

Yes. For new builds we focus on ventilation, construction details and what remains under warranty.

What does it cost?

Fees are fixed before we attend and published on our prices page.

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