Basements and cellars
A tanking guarantee in the pack shows a date that has passed on the face of the page. What current condition of the tanking has that old date not described?
That old date has not described the current condition of the tanking. The guarantee in the pack shows a date that has already passed on the face of the page, so the paper is outside the period it states. A lapsed date does not say the tanking is failing, and it does not say the tanking is still doing its job. The survey has recorded what the document shows. It has not tested the membrane and it has not renewed the guarantee.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A tanking guarantee is a promise by an installer or a system provider for the period printed on it. When that date has passed, you have the wall as it is, not a live promise. The basement can look dry on the day and the paper can still be expired. It can look damp and the paper would still not prove the cause. The survey reads the date. It does not become the guarantor, and it does not see behind the tanking.
Ask the solicitor who issued the guarantee, whether it could ever transfer, and what the date limits. Do not tell a lender the basement is still guaranteed if the date on the page has passed. If you need the present condition, that is an inspection of what can be seen now, not a reading of an old certificate. The survey has not extended the cover and it has not condemned the tanking.
What should you ask your surveyor?
- Has the date on the tanking guarantee already passed?
- Does that date describe the tanking's current condition, or only the old paper?
- Was the membrane itself left untested?
What are the typical next steps?
- Treat the passed date as an expired paper, not a condition report.
- Ask the solicitor what the guarantee date actually limits.
- Do not tell a lender the tanking is still covered.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If the walls look dry, has the guarantee effectively continued?
No. A dry day does not move a date that has already passed on the face of the page. The paper is outside its stated period whatever the walls look like. The survey has not tested the tanking and has not renewed the guarantee. Dry finishes are not a current description written by that old date.
Can the seller's word extend the guarantee?
Not by itself. The date is on the document. A conversation does not reprint it. The solicitor needs the actual guarantee, the issuer and any term about transfer. The survey has not extended the cover. Until the paper says something different, the old date still has not described the tanking today.