www.ultimatehandyman.co.uk

need a bit of help with a rather strange problem cannot get my head around.

about 3 years ago bought a wreck to do up.

solid terraced victorian property, suspended timber floors, 2 foot crawl space below. lots of problems with damp, water egress not being properly dealt with etc. we ended up stripping the whole property back to brick all external walls, and rebuilt a large section of flooring in hallway which was completely rotten.

in the downstairs hallway, on the ground floor in line with the edge of the stairs going up a patch of floor boards remained damp. everything else dried out fine.

looking under basement the underside of these floor boards were sopping wet, with literally water droplets hanging off them. it also tasted like sea water.
We therefore concluded it was probably salt ingress in boards and a hygroscopic phenomenon.

decided to rip boards up - 3 wide and replaced with old boards to match taken from upstairs. laid some DPC in between new boards and joists just in case something on joists was seeping through. Also added another air brick in crawl space to improve ventilation, although no other signs damp.

fast forward 6 months and wet patch has returned (!).

underside of board, including DPC is bone dry. but top is deffo 'wet'.
there are no pipes in area and no other signs water leak. The damp patch does not spread to edge of board at wall - its in middle. anyhow there is a good gap at edge of board and wall. joist is dry.

rest of house is bone dry. dot and dabbed insulated PB to all walls. temperature very moderate even now its turned cold. crawl space floor is broken bricks etc. no real concrete topper.

I cant work out what has caused it? We would like to sand and oil boards which I am obviously reluctant to do when it is wet?

any ideas? you can see its spreading off the main board and weeping into adjacent board now? Ive added a further air brick to that section of crawl space, but I don't really think its coming from there as underside of board is completely dry? worth putting some plastic down on crawl space floor? or will that cause further problems?

thanks

If the bottom/underside of the board is dry, then it must be coming from above, or you have an animal you do not yet know about.

You could try leaving a serving tray or old cooking tray on said patch and leave it for a long while.

If it helps, I had a tiny leak from the toilet (No, don't ask, no really don't) I got an old mobile phone (fully charged battery) set it to record video, put it on the floor looking at the toilet, left it for quite a few hours. It didn't solve the problem (never thought it would) but I did find where it was leaking from.

If you have a washing machine close by check the water supply hand turn nut is tight. I have seen a number of drip leaks from them causing issues like this. The drip can spread over time by capillary action. I found a damp wall 6 feet away in a friend's house. A charlatan damp expert had diagnosed a breached damp course. Fixed with a new hose for a couple of quid. I am not saying this is it for you but worth checking.

DWD

thanks guys.

House currently empty - as still being renovated.

kitchen is miles away. no water pipes near, central heating goes in the above floor but the ceiling is pristine - no water marks at all

House empty, no reason not to put a tray on damp patch, you have noting to lose.