I am just starting on some internal renovation work on my new house and when i lifted up the carpets there seems to be a very distinct and succinct line of wet/dampness on the floorboards which is only and exactly where the walls are, its roughly 10cm outwards and it doesnt seem to go IN the room just on the outside (hallway). None of the rooms shown are bathrooms or ensuites so im assuming it probably isnt a waterpipe or similar.
The boards themselves dont actually feel damp or anything, they are just slightly colder when you touch that area and obviously you can tell they are not fully dry due to the darkness of the colour. any initial thoughts as to what this may be? Thank you