ᐅ Timber Extension – Thermal Bridge at Floor – Moist Floor During Sauna Use
Created on: 11 Jan 2016 11:09
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Vatos83Hello,
we had a wooden extension built on the back of the building on the terrace slabs.
For this, point foundations were poured for the wooden posts, the side walls were insulated and clad, and beams were attached to the house facade to create the roof slope. The terrace slabs are laid on frost protection and gravel. We have integrated a sauna, and during the first heating, we noticed that moisture collects on the outer terrace slabs near the exterior wall, on the outdoor side facing the interior, likely due to the lack of insulation outward under the floor slabs. The floor slabs run continuously from the interior to the outside. When ventilated, the slabs do dry out again. The entire wooden wall has about 1 to 1.5 cm (0.4 to 0.6 inches) clearance from the floor, and spray foam was applied underneath. Basically, the question is whether this is harmful to the wooden construction and if the terrace slabs should be removed to install insulation, or if this issue is not a concern.
I would appreciate any feedback,
Thank you.
we had a wooden extension built on the back of the building on the terrace slabs.
For this, point foundations were poured for the wooden posts, the side walls were insulated and clad, and beams were attached to the house facade to create the roof slope. The terrace slabs are laid on frost protection and gravel. We have integrated a sauna, and during the first heating, we noticed that moisture collects on the outer terrace slabs near the exterior wall, on the outdoor side facing the interior, likely due to the lack of insulation outward under the floor slabs. The floor slabs run continuously from the interior to the outside. When ventilated, the slabs do dry out again. The entire wooden wall has about 1 to 1.5 cm (0.4 to 0.6 inches) clearance from the floor, and spray foam was applied underneath. Basically, the question is whether this is harmful to the wooden construction and if the terrace slabs should be removed to install insulation, or if this issue is not a concern.
I would appreciate any feedback,
Thank you.
Well observed: missing insulation and likely inadequate air sealing leading to convection of very warm, humid air into the wooden structure. Over time, this can cause moisture accumulation, mold growth, and wood decay, for example, between the exterior wall and spray foam insulation. Wooden components may become wet but should be designed and installed in a way that allows them to dry out without problems. Moisture buildup must be avoided at all costs. Allow sufficient airflow on all sides.
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fach1werk24 May 2016 14:35A sauna always has a temperature just above 20°C (68°F) near the floor. Under these conditions, it must have exhaust vents.
If it is used infrequently (private use), it may be sufficient not to seal the floor tightly; air must be able to flow in. So no foam, no silicone, no polystyrene.
If it is used more frequently, forced ventilation with a small duct fan is necessary. The duct must have a slight downward slope toward the outside, and the duct should be insulated. Otherwise, condensate will run toward the wood. Where there is exhaust air, there must also be supply air. This supply air does not require a fan.
Sealing the sauna tightly to the floor is not recommended; it is only done for liability reasons, for example, if the sauna needs to be secured.
Uninsulated patio slabs used as a base remain thermal bridges, where condensation will occur. However, the wood—especially slow-grown Nordic wood—can handle this if the sauna is allowed to breathe and is not sealed tightly to the floor.
Enjoy your sauna experience!
fach1werk
If it is used infrequently (private use), it may be sufficient not to seal the floor tightly; air must be able to flow in. So no foam, no silicone, no polystyrene.
If it is used more frequently, forced ventilation with a small duct fan is necessary. The duct must have a slight downward slope toward the outside, and the duct should be insulated. Otherwise, condensate will run toward the wood. Where there is exhaust air, there must also be supply air. This supply air does not require a fan.
Sealing the sauna tightly to the floor is not recommended; it is only done for liability reasons, for example, if the sauna needs to be secured.
Uninsulated patio slabs used as a base remain thermal bridges, where condensation will occur. However, the wood—especially slow-grown Nordic wood—can handle this if the sauna is allowed to breathe and is not sealed tightly to the floor.
Enjoy your sauna experience!
fach1werk
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