Age and type of house
The ground floor of the barn was a livestock stand and is now a slab. What damp-proofing under that slab was not verified?
The damp-proofing under the slab was not verified at all. The ground floor was a livestock stand and is now a slab, and the survey could see only the top surface. Any membrane, tanking or damp-proof course beneath that concrete was hidden. A dry floor on the day does not prove a barrier is there, and a livestock floor was often built for animals rather than as a domestic damp-proofed slab. The visit has not confirmed what, if anything, was placed under the new concrete.
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?
When a barn floor is covered with a slab, the old surface disappears. The surveyor can note cracks, levels, salt and any damp marks on top. They cannot say a membrane was lapped, punctured or omitted. Livestock stands were washed down and loaded by animals. Pouring concrete over that history does not let a visual inspection certify the build-up. A moisture comment on the surface, if one was made, stays a surface comment. It is not a view under the slab.
Ask the seller, through your solicitor, for any specification or guarantee that names a damp-proof membrane under this slab. If nobody can show one, do not write it into the survey. A specialist can advise only after they are clear the membrane was not seen. Do not break out the slab yourself to look. The home survey has recorded a slab over a former livestock floor, not a verified damp-proofing detail.
What should you ask your surveyor?
- Did you see only the top of the slab, with nothing of the layers beneath?
- Were any damp marks on the surface, or was the slab dry to the eye?
- Was a membrane specification shown to you, or not?
What are the typical next steps?
- Treat damp-proofing under the slab as not verified.
- Ask the solicitor for any membrane specification or guarantee.
- Do not break out the slab yourself to look underneath.
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 room smells fresh, is the membrane proved?
No. Smell does not show layers under concrete. The livestock floor has been covered, and the survey did not verify a membrane, tanking or damp-proof course beneath the slab. Fresh air in the room is not a barrier under the concrete.
Does a new screed on top count as damp-proofing?
No. A screed is a finish on the slab. It is not evidence of a barrier underneath. The survey could not see that barrier and has not verified it. The old livestock floor remains hidden, so any barrier stays unverified.