Solum and Damp Floorboard(s) Next to Hearth

[Blueyes]

Another ongoing damp puzzle and would really appreciate some insight and help....

Thought I had solved the damp floorboards adjacent to an old electric fire by removing, removing wet rubble in the chimmney void and allowing ash pit to dry out before reinstating a new constructional hearth.

2 x new air bricks and a total of 5 x airbricks for this room. 3 x in front bay and 2 x in end terrace. Lots of air movement now.

However, the damp patch on floorboard has returned. Warm humid time of year but the ventilation with windows and floor up has been good. I dont think it's air from the flue but could be.

Is it the damp solum below the suspended floor causing me this grief? Can I remedy the cracked Victorion bitumen with a liquid DPM? Aggregate? Geocell? Mechanical Ventilation £££? It's clay soil where the bitumen has perished.

It's a real puzzle and I dont want to reinstate flooring, new stove and then sit back on the sofa to see damp floorboards return, tricky one.

I have tried to post some pics..

Many thanks all

 

[Blueyes]

And some more recent pics...

 

[Pennyviz]

Sure you've thought of this, but have you checked the chimney, water can travel in weird directions sometimes.

 

[paulc]

Is there any DPC under the joists that are resting on bricks ?
It would be worth jacking them up and inserting a strip of DPC material underneath each one.

 

[Zebra]

Could it just be condensation, where the warm moist air hits the cold hearth? I get it in my fireplace this time of year, well, a little earlier in the year to be fair, when the air is warmer than the masonry.

 

[a twig]

Having regular fires always helps

 

[Matt Green]

Could be hygroscopic salts within the edge of the board from the old hearth are now absorbing moisture from the air. Can you switch the board with another one and see if the water mark reappears in the new position?

 

[CliffordPope]

Could be hygroscopic salts within the edge of the board from the old hearth are now absorbing moisture from the air.

I agree. Salts impregnated in boards or masonry or plaster can replicate and perpetuate a condensation problem long after the root problem has been cured.
Look at salt stored in a jar. No matter how carefully you wipe it and try to keep it dry, the threads quickly become damp and the outside starts to glisten with moisture.

 

[Blueyes]

Hello All

Apologies for dealy, thanks so much for the replies and ideas on this.

I have swapped floorboards and will await to see what happens.

It's 75% RH in the lounge so I suspect humidity condensation is an issue as one poster suggests. I have already added airbricks but agree regualr fires and heating would help.

To treat the solum where the bitumen has cracked to reveal large ares of clay soil what would people do ?

 

[Blueyes]

Currently looking at geocell recycled glass foam aggregate over the cracked bitumen solum as I have a huge load of it leftover from Mike Wye.....

Some posts here http://red.coop/suspendedtimberfloors but yet to meet anyone who has done this, wonder if it would stop moisture from clay soil.

Will keep you posted in case it's of interest to anyone else with high humidity under suspended floors....