It's a mystery that's got everybody scratching their heads

HI everybody, can you help me please, it's a real mystery what's going on with our 'damp' problem that thus far, it's left 6 tradesmen and a building engineer with ice packs on their heads.

It started off with there being no DPM installed when the fireplaces and hearths were replaced by the previous owners. The concrete bed on one was crumbling which led to further investigation to discover both beds were wet through and damp was being drawn to the breast, walls and in one, the floorboards. We've dug them out, hacked off the plaster and let it dry naturally.

However, on one the floorboards won't dry. We've removed all nails and put a DPM along the joist and it's continually wet, I've been underneath to see if the boards are in contact with anything that would allow moisture to travel - nothing is in direct contact - they've been left for 5 weeks, boards to the side have been removed to help airflow, the damp doesn't travel, it's static.

Applying heat, they change colour as if to be drying, only for when the heat is turned off, an hour later they're sodden again - but there is no water source, nothing acting as a wick and to cap it all, it's only the boards in front of the hearth that was. Nobody thus far can explain it, we've checked airflows, they're OK, we are well and truly confused and running out of ideas. I know I could chop them and put moisture board in (which will eventually happen) but before we do, I'd like a solution and cure, not a short term fix. I've attached a few photos of the job and any sensible help and advice is more than welcome.

 

Ha..KIAB, I'm seriously beginning to think it's a haunting. We've been through your suggestion, the boards where wet now have no direct contact with anything other than a DP membrane running across the joist - the joist which is dry. If you look on the DSC photo and the damp marks - they've not changed in 5 weeks - in that time, everything literally underneath and to the sides has been removed - I apply heat it looks as if it's drying, an hour later sodden again but there is no water source. I also went down the line that the house was acting as a vacuum but the engineer said it's possible but not in this case because the markings and levels (I marked them off in pencil) don't change...spooky eh?

 

Property is 1937, the boards are only wet where the hearth was, the 'wet' doesn't travel or spread, it's static. The boards along the edge of the hearth side have been lifted (prised) to remove any nails and other debris and a DPM layer run along the joist from the wall to beyond the far edge of the hearth that was. Since the DPM was slid under, it's actually got worse - that's where it becomes even more confusing and they've stayed wet ever since, but to reiterate the wet is static, the boards are in contact only with a DPM with no cables or pipes attached underneath, the joist they were resting on is dry..so you see - understand why it's confusing as it doesn't follow any protocols i.e pipe spraying, wicking or in contact with a water source. I know they'll have to be chopped but we need to find out why it's happening in just one section - cure what ever is going on!

And it doesn't smell damp - just to throw another spanner in the works!

 

Sorry guys, I should mention - prior to the DPM layer being put under the boards and along the joist - at least once a day, they would change colour - as if drying out, only to return almost black with moisture.

 

Oh they're wet teabreak, the damp meter had an orgasm (we've tried 3 different machines) when it was put on them, I also marked the boards off to where it was orgasmic then stopped screaming, the staining hasn't moved, it used to just change colour - they've warped due to expansion and contraction into a barrell sort of shape caused by moisture.

 

No KIAB, no water pipes.

 

DPM - in this photo it looks as if it's drying out (colouring) and for a while - well overnight, we thought so too until the morning where it was wet again..

 

No chippie244, it's a 1937 semi. But we've looked at the water tables, tidal effects and so on as it was mentioned fitting a pump - though the pump would have nothing to pump away as there is no water pooling and the air flows are good.

 

I see where you're going KIAB but unfortunately no it isn't.