We have bought a 1.5 story house built in 1979 where the inspection showed elevated moisture levels in the sill under the heart wall. The moisture content measured was 17.3%, which is above the threshold of 17% where microbial growth may occur. However, neither we nor the inspector detect any bad odor in the house.
Since the house has an older but well-maintained standard, we will renovate both bathrooms, support the heart wall, create an open floor plan between the kitchen and living room, and replace the surfaces in most rooms. Since we are already planning extensive renovations on the house, it seems prudent to replace the sill because it is a risk construction with a pressure-treated sill and has elevated moisture levels. Should we also consider installing mechanically ventilated floors, or is that likely unnecessary since there is no bad odor in the house (a sign of microbial growth)?
Is it usually sufficient to only replace the sill under the heart wall, or should the sill under the exterior walls be replaced as well?
We will probably conduct a more in-depth investigation by an inspector to answer some of our questions, but I would love to hear what you think if anyone has had similar experiences, etc.?
Since the house has an older but well-maintained standard, we will renovate both bathrooms, support the heart wall, create an open floor plan between the kitchen and living room, and replace the surfaces in most rooms. Since we are already planning extensive renovations on the house, it seems prudent to replace the sill because it is a risk construction with a pressure-treated sill and has elevated moisture levels. Should we also consider installing mechanically ventilated floors, or is that likely unnecessary since there is no bad odor in the house (a sign of microbial growth)?
Is it usually sufficient to only replace the sill under the heart wall, or should the sill under the exterior walls be replaced as well?
We will probably conduct a more in-depth investigation by an inspector to answer some of our questions, but I would love to hear what you think if anyone has had similar experiences, etc.?
Hello and welcome to the Byggahus forum!
It is difficult to give good advice without knowing more precisely how the house is built. I am primarily thinking about the foundation slab and the floor on the ground floor, as well as the exterior walls. The presence of pressure-treated wood suggests that the slab lacks underlying insulation, which is a potential problem. I am not an expert on the health aspects of pressure-treated wood, but I suspect that the pressure-treated wood in your case belongs to an older and more hazardous type. Without knowing more, however, it remains speculation.
It is difficult to give good advice without knowing more precisely how the house is built. I am primarily thinking about the foundation slab and the floor on the ground floor, as well as the exterior walls. The presence of pressure-treated wood suggests that the slab lacks underlying insulation, which is a potential problem. I am not an expert on the health aspects of pressure-treated wood, but I suspect that the pressure-treated wood in your case belongs to an older and more hazardous type. Without knowing more, however, it remains speculation.
Thanks for the welcome and reply!J justusandersson said:
The foundation consists of an uninsulated slab on ground with plastic foil, 70 mm cell plastic, and 22 mm particle board (according to the original building permit application).
Since high moisture levels have been measured, it might be more evident that we should replace the sole plates. If the moisture content was okay but the problem was only with the pressure-treated sole plates, it might have been a different situation and we could keep them since there is no odor... And then investigate what type of pressure treatment it is, etc. Or what do you think?
If you have particle board, plastic foil, and foam insulation on top of the concrete, everything is fine except in places where wood must lie against the concrete. In those cases, pressure treatment is a minor issue but not the main problem. The concrete becomes damp in areas where water vapor from warm indoor air can descend and condense on the cold concrete. Since the measured moisture content in the base plate of the load-bearing wall is not higher than a little over 17%, I suspect there might be a vapor barrier between the concrete and the base plate. Ideally, you should place an inorganic and thermal insulating material, such as clay block, between the concrete slab and the base plate. How to deal with the outer walls depends partly on the moisture content in the base plate there and partly on the possibilities of ventilating the base plate towards the outside.
I think you should start by measuring the moisture in the sills of the exterior walls as well and take the discussion further from there. Ventilating towards the outside means ensuring that the smell does not get in.