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damp meter
Pretty sure those are just for timber, sticking it on a wall won’t tell you anything useful. You could check the roof members in the loft though.
The wall ones work on walls. They have little prongs that pierce into the plaster to take a reading. Do it behind a thing so the owners don’t notice the little holes and get upset.
https://www.amazon.co.uk/Moisture-Firewood-Handheld-Detector-Backlight/dp/B08NF56FGG/ref=asc_df_B08NF56FGG/?tag=googshopuk-21&linkCode=df0&hvadid=499390094390&hvpos=&hvnetw=g&hvrand=9023063221788643964&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1006598&hvtargid=pla-1245165363099&psc=1
@dbr started
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