Subfloor Ventilation
Discussion
Hi
I am working on resolving a damp issue in my new (to me!) old house and wanted to see if anyone had experienced a similar issue and found a solution that worked.
Our house has suspended wooden floors over a 30cm ish void and one external wall of the house is damp in places along the bottom. When we moved in that side of the house had broken gutters, a leaking gulley and has a concrete path that is too high. The gutters have been replaced, and the gulley fixed, and the path is on the list to dig out so the drying process has started, but I want to give the wall the best chance of drying out.
I have lifted the floors to take a look, and it's only two corners that are damp in the subfloor void - these are either side of an extension put up some time ago on the original back wall of the house. Everything else I can see in the void (the timbers and the oversite) are all dry and in good condition. There are several airbricks at the front of the house, the sides and the back, but I am wondering if the air-flow to the corners could be improved. Whilst the floor is up a dehumidifier is working away, but I am not sure how long I can persuade my other half that having the flooring up in two rooms downstairs is normal. I reckon I have four weeks at best!
In terms of options for improving things I did come across this MORI WMF fan https://eltafans.com/product/mori-wmf/ which seems designed for the purpose, although apparently isn't suited to be connected to ducting. I have a small utility room downstairs where I could get ongoing access to the subfloor so I was thinking having an inline fan in there ducted to the problem areas might be easier as I can get access to the fan and and direct outside air to the two problem corners - there seem to be low wattage fans around (10 to 12w) that could be left on for all/most of the time for a manageable cost. I guess I could also just run some ventliation ducts around the subfloor area to direct air from the air-vents to the problem areas more directly which is what my builder has suggested is the normal approach.
Has any one tried any of these approaches and had good results?
I am working on resolving a damp issue in my new (to me!) old house and wanted to see if anyone had experienced a similar issue and found a solution that worked.
Our house has suspended wooden floors over a 30cm ish void and one external wall of the house is damp in places along the bottom. When we moved in that side of the house had broken gutters, a leaking gulley and has a concrete path that is too high. The gutters have been replaced, and the gulley fixed, and the path is on the list to dig out so the drying process has started, but I want to give the wall the best chance of drying out.
I have lifted the floors to take a look, and it's only two corners that are damp in the subfloor void - these are either side of an extension put up some time ago on the original back wall of the house. Everything else I can see in the void (the timbers and the oversite) are all dry and in good condition. There are several airbricks at the front of the house, the sides and the back, but I am wondering if the air-flow to the corners could be improved. Whilst the floor is up a dehumidifier is working away, but I am not sure how long I can persuade my other half that having the flooring up in two rooms downstairs is normal. I reckon I have four weeks at best!
In terms of options for improving things I did come across this MORI WMF fan https://eltafans.com/product/mori-wmf/ which seems designed for the purpose, although apparently isn't suited to be connected to ducting. I have a small utility room downstairs where I could get ongoing access to the subfloor so I was thinking having an inline fan in there ducted to the problem areas might be easier as I can get access to the fan and and direct outside air to the two problem corners - there seem to be low wattage fans around (10 to 12w) that could be left on for all/most of the time for a manageable cost. I guess I could also just run some ventliation ducts around the subfloor area to direct air from the air-vents to the problem areas more directly which is what my builder has suggested is the normal approach.
Has any one tried any of these approaches and had good results?
Hi Phil
Glad you found the thread!
I ended up not going for the fan as they didn't recommend it with any length of ducting when I called them, and I couldn't see how to get the fan installed without it.
We ended up finding two issues - digging up the concrete path that runs alongside the house resolved the issue on the corner between the extension and the old house and we also found another damp area close to it adjacent to a chimney breast. After a fair amount of head scratching we found a crack in the render on the outside of the chimney breast (our house is detached and has outside chimney breasts if that makes sense) - the crack was on an internal corner and at first floor level so not that obvious from down below. We removed and replaced all the blown render, repainted, and the chimney breast and floor is slowly drying out with the help of a dehumidifier. The big clue for us was that this second area got noticeably worse after a heavy rain, and we were lucky enough to have a few heavy storms in a row which gave us the clue that rainwater was getting in.
Hope that helps, good luck getting it resolved. I still like the idea of the fan and getting fresh air down into the void, just haven't found a solution.
Glad you found the thread!
I ended up not going for the fan as they didn't recommend it with any length of ducting when I called them, and I couldn't see how to get the fan installed without it.
We ended up finding two issues - digging up the concrete path that runs alongside the house resolved the issue on the corner between the extension and the old house and we also found another damp area close to it adjacent to a chimney breast. After a fair amount of head scratching we found a crack in the render on the outside of the chimney breast (our house is detached and has outside chimney breasts if that makes sense) - the crack was on an internal corner and at first floor level so not that obvious from down below. We removed and replaced all the blown render, repainted, and the chimney breast and floor is slowly drying out with the help of a dehumidifier. The big clue for us was that this second area got noticeably worse after a heavy rain, and we were lucky enough to have a few heavy storms in a row which gave us the clue that rainwater was getting in.
Hope that helps, good luck getting it resolved. I still like the idea of the fan and getting fresh air down into the void, just haven't found a solution.
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