Damp and moisture meters
Why do surveyors compare a moisture reading with a dry part of the same house?
Because the useful information is the pattern, not a single number. A reading means more when it is set against a dry part of the same wall, with the same meter, on the same day. Without that, you cannot tell a wet patch from a lining that always reads high.
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?
Meters are comparative aids. Pins and pads respond to different things, including salts and metal. A percentage on a screen is not a government standard and it is not a water content you can take to a lender as a laboratory result. What a careful surveyor can say is that one area responded more than another, and what the eye could see there.
If the report gives a number and nowhere to compare it with, ask for the comparison and the location while the firm still has the site notes. The Property Care Association’s advice is to diagnose the building. A lone number is not that diagnosis, and it is not a reason to start injection before exchange.
What should you ask your surveyor?
- Was a comparison reading taken on a dry part of the same construction?
- Where, exactly, were the higher readings?
- What could you see at the high spot that you could not see at the comparison spot?
What are the typical next steps?
- Email the firm and ask for the comparison and the meter type in writing.
- Do not let a contractor turn one number into a whole-house treatment.
- If no comparison was taken, say so when you decide whether to investigate further.
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
Is a higher reading always wetter?
Not always. Foil, salts and metal can lift a reading on a dry lining. That is why the surface and the meter type matter.
Should the report print every reading?
A long list of numbers without locations is not more useful. Locations and what was seen matter more than a spreadsheet.