Appropriate to place studs or sill below the level of self-leveling compound?
Our builder has erected wooden studs with a sill/bottom plate for a wall between the bathroom and the hall. Self-leveling compound will be filled up against the stud or the finished wall. In the bathroom, waterproofing, adhesive, and tiles will be applied. In the hall, adhesive and tiles will be laid. The bottom plate/sill will end up approximately 20-30 mm below the finished floor level. I am concerned that moisture will find its way into the timber, causing it to eventually rot. Is it appropriate to do it this way, or what should be done?
That is how it is usually done; you seal against the plasterboard with a foam strip, then the waterproof layer is applied. If everything is done correctly, no water will reach the sill.
Thank you, Andreas! I understand that the waterproofing on the floor and wall inside the bathroom prevents water from seeping down there. But if you have a shoe rack with snowy shoes in the hallway or mop the floor with water, there's nothing to prevent water from finding its way down between the tiles and then through the leveling compound to the layer the sill is on. If it were dead material that doesn't rot, nothing would happen, but lumber in that position with one side against the waterproofing doesn’t get much ventilation and will likely absorb and retain the water. Maybe there was something about the foam strip I didn't understand; does it prevent water that has passed the leveling compound from spreading under the gypsum at the next level? Or do you apply waterproofing on the hallway side as well?Andreas_kalmar said:
Grateful if you could explain the thinking behind this.
The foam strip prevents the water in the filler from being absorbed into the wall and provides a movement joint between the wall and the filler. If you have such amounts of water in the hall that it would damage the sill, then you have bigger concerns. You probably have underfloor heating that dries the floor, so mopping or wet shoes shouldn't be a problem. Best regards, Andreas
Thank you, Andreas. I now understand the function of the foam strip. Movement occurs between the wall and the floor due to different directed forces and has inherent different linear expansion along the joint instead of randomly, which would be unfortunate if, for instance, cracks appeared between the tiles. Additionally, it protects the drywall from moisture from the self-leveling compound when it dries. However, it does not protect against water seeping through the self-leveling compound and propagating towards the baseplate, which I am concerned about.
Installing underfloor heating reduces the amount of water penetrating because the water mostly evaporates instead of seeping down. But isn't it possible that the underfloor heating may rarely or never turn on and heat during summer in a hallway since the house doesn't require significant heating, only ventilation? Moreover, one cannot be entirely sure that no one will adjust the settings so that the floor is without heating for a period. Therefore, I think the construction itself should be 100% secure without relying on underfloor heating. Alternatively, there should be conditions for the use of the house that underfloor heating should always be on, which cannot be assumed, for example, in a vacation home.
When I try to imagine what can happen, I envision that over several decades it is not uncommon for a house to experience a temporary or sometimes repeated amount of water seeping through the self-leveling compound, and then no part that can rot should absorb water in the floor because the drying at this spot in the floor against a sealed bathroom side becomes very slow. If the layer under the self-leveling compound is easily penetrable by water, then in the best case, the water can continue downward. This becomes dependent on whether water seeps through the self-leveling compound faster than it drains through the next layer, as well as the capillary action laterally. Then it's a matter of direct contact between the baseplate and the dripping water.
Furthermore, I can imagine that the humidity that arises in the floor under the self-leveling compound causes a wooden baseplate to absorb moisture long before the air becomes saturated enough for the water to condense. The humidity will also be affected by the humidity and temperature in the underlying layers. I can imagine a stone foundation is both relatively moist and cools in a disadvantageous way. Sincerely, concerned about embedded wood in the floor.
Installing underfloor heating reduces the amount of water penetrating because the water mostly evaporates instead of seeping down. But isn't it possible that the underfloor heating may rarely or never turn on and heat during summer in a hallway since the house doesn't require significant heating, only ventilation? Moreover, one cannot be entirely sure that no one will adjust the settings so that the floor is without heating for a period. Therefore, I think the construction itself should be 100% secure without relying on underfloor heating. Alternatively, there should be conditions for the use of the house that underfloor heating should always be on, which cannot be assumed, for example, in a vacation home.
When I try to imagine what can happen, I envision that over several decades it is not uncommon for a house to experience a temporary or sometimes repeated amount of water seeping through the self-leveling compound, and then no part that can rot should absorb water in the floor because the drying at this spot in the floor against a sealed bathroom side becomes very slow. If the layer under the self-leveling compound is easily penetrable by water, then in the best case, the water can continue downward. This becomes dependent on whether water seeps through the self-leveling compound faster than it drains through the next layer, as well as the capillary action laterally. Then it's a matter of direct contact between the baseplate and the dripping water.
Furthermore, I can imagine that the humidity that arises in the floor under the self-leveling compound causes a wooden baseplate to absorb moisture long before the air becomes saturated enough for the water to condense. The humidity will also be affected by the humidity and temperature in the underlying layers. I can imagine a stone foundation is both relatively moist and cools in a disadvantageous way. Sincerely, concerned about embedded wood in the floor.
The same problem is indeed with gypsum baseboards etc. If you are worried, ask the tiler to install a waterproofing strip in the floor/wall angle in the hallway as well, then you will probably sleep well afterwards. Best regards, Andreas