This is a really confusing problem, which seems unsolvable. I live in a purpose built maisonette built approximately in 1910. (Tried to add pics but am told they are too large)
It’s best to begin at the beginning!
Just before Covid I noticed an internal party wall showing minor signs of damp-paper starting to separate from wall and some plaster beneath starting to crumble. I used Solvite to paste paper back and this worked, but not around chimney breast area. My new neighbour happened to call round asking if I had damp issues as he had following a chemically injected damp course the previous owners had installed before he moved in. I had had no issues before that damp course was installed! I went the usual route and was diagnosed with rising damp! Unsure of this I hired an independent surveyor who advised on remedial treatment involving water inhibiting sand/cement re rendering on bare brickwork, but no chemical injection. I went ahead with this and also had a French drain installed on the opposite outside wall and some brick re pointing. That was in October 2021.
However, and this is the new issue-when I lifted up the carpets in preparation for the work there was a wetness on the floorboards on the edge of the constructional hearth-carpets/underlay all dry. The surveyor I had previously used suggested I open up the area and dry it all out and replace boards. On lifting several boards around the fireplace I noticed a damp joist around fire place near the constructional hearth, more on one side than the other. The dampness increased and decreased according to the humidity levels in the room. I use a ThermPro Monitor to measure the humidity.
I hired another independent surveyor in March 2022 who recommended either
a) leave suitable time for everything to dry out and then replace damaged woodwork, ensuring it doesn’t touch the constructional hearth or masonry and put a damp membrane on the ends. Or
b) remove the whole stone fire surround, installed 15 years ago, replace all the constructional hearth and then as a).
The fire surround is fixed with a special adhesive so would be a massive job to remove.
In May, I hired a carpenter to cut the floorboards touching the constructional hearth so I could open up the area around the hearth. I turned these so that the edges were facing the other way but still upwards and these still get wet even though the edges are no where near the hearth! The edges which now touch the hearth don’t get wet!
I have used newspaper to gauge any wetness in corners around fireplace and this has got wet, not soaked though. The wet joist on the left seems to have a pattern/shape of wetness; it’s not soaked through and continues to the middle of the floor and then stops. It is near but not against the constructional hearth. On the right side the joist near the hearth just has patches here and there but does not continue to the middle of the floor. It actually touches the constructional hearth. All other joists are fine.
I took off the top layer of the constructional hearth as it was crumbly but this does not seem wet.
There don’t seem to be any leaking pipes and the ground subfloor does not seem wet.
I have taken out a lot of rubble, bricks slates etc from under the floor but not all of it.
There are two airbricks on the opposite outside window wall. The room is about 15 foot long.
It may be worth adding that my neighbour investigated his issue and found he had a leaking mains pipe and had to have all his floor removed, floor dried out and a new floor installed! Whether this has any bearing on my issue I am unsure. I have also had the chimney swept and some re pointing of the chimney stack.
Can anyone advise me? I really want to resolve this and get on with some decorating.
It’s best to begin at the beginning!
Just before Covid I noticed an internal party wall showing minor signs of damp-paper starting to separate from wall and some plaster beneath starting to crumble. I used Solvite to paste paper back and this worked, but not around chimney breast area. My new neighbour happened to call round asking if I had damp issues as he had following a chemically injected damp course the previous owners had installed before he moved in. I had had no issues before that damp course was installed! I went the usual route and was diagnosed with rising damp! Unsure of this I hired an independent surveyor who advised on remedial treatment involving water inhibiting sand/cement re rendering on bare brickwork, but no chemical injection. I went ahead with this and also had a French drain installed on the opposite outside wall and some brick re pointing. That was in October 2021.
However, and this is the new issue-when I lifted up the carpets in preparation for the work there was a wetness on the floorboards on the edge of the constructional hearth-carpets/underlay all dry. The surveyor I had previously used suggested I open up the area and dry it all out and replace boards. On lifting several boards around the fireplace I noticed a damp joist around fire place near the constructional hearth, more on one side than the other. The dampness increased and decreased according to the humidity levels in the room. I use a ThermPro Monitor to measure the humidity.
I hired another independent surveyor in March 2022 who recommended either
a) leave suitable time for everything to dry out and then replace damaged woodwork, ensuring it doesn’t touch the constructional hearth or masonry and put a damp membrane on the ends. Or
b) remove the whole stone fire surround, installed 15 years ago, replace all the constructional hearth and then as a).
The fire surround is fixed with a special adhesive so would be a massive job to remove.
In May, I hired a carpenter to cut the floorboards touching the constructional hearth so I could open up the area around the hearth. I turned these so that the edges were facing the other way but still upwards and these still get wet even though the edges are no where near the hearth! The edges which now touch the hearth don’t get wet!
I have used newspaper to gauge any wetness in corners around fireplace and this has got wet, not soaked though. The wet joist on the left seems to have a pattern/shape of wetness; it’s not soaked through and continues to the middle of the floor and then stops. It is near but not against the constructional hearth. On the right side the joist near the hearth just has patches here and there but does not continue to the middle of the floor. It actually touches the constructional hearth. All other joists are fine.
I took off the top layer of the constructional hearth as it was crumbly but this does not seem wet.
There don’t seem to be any leaking pipes and the ground subfloor does not seem wet.
I have taken out a lot of rubble, bricks slates etc from under the floor but not all of it.
There are two airbricks on the opposite outside window wall. The room is about 15 foot long.
It may be worth adding that my neighbour investigated his issue and found he had a leaking mains pipe and had to have all his floor removed, floor dried out and a new floor installed! Whether this has any bearing on my issue I am unsure. I have also had the chimney swept and some re pointing of the chimney stack.
Can anyone advise me? I really want to resolve this and get on with some decorating.