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So the floor boards are wet coming starting from the external walls. The cavity’s are dry and so is underneath

The underlay was soaked showing a considerable about of water

Also the underside of the floor boards are dry

I have this in multiple places around the house

It’s causing hell with young children and mould so any help would be appreciated

Hi Ethanm16@icloud.com,
The most likely cause is that insulation backed boards have been fitted to the walls. Condensation may be forming behind the boards and running down ending up on your floorboards.
If you can measure humidity levels and establish dew point temperature and the temperature of the walls behind the boarding this should show if this is the issue.
If it is dehumidifiers may be the only solution.
Regards S

Hello thanks for your reply. Unfortunately there’s no insulation backing boards. So still a head scratcher on this one. The floor boards to but up hard to the blocks and they are around 26% on the damp meter. Could the wood be drawing the moisture out the blocks ?

Hi ethanm16@icloud.com,
At 26% damp reading it is unlikely that the walls are wet enough to create the problem you have. Is there a damp-proof membrane either fixed to the walls or as an integral part of the boarding?
Regards S