Hello everyone,
My house from the 1960s had a basement party room that was later also used as a bedroom. Now it is going to be converted into an office space. There are two large windows, and heating is provided by a radiator on the wall, so no underfloor heating.
Previously, there was a damaged wooden plank floor. It has been removed, and I have about 7cm (3 inches) plus 1cm (0.4 inches) of new floor covering height available to reach the level of the tiled hallway. There are a few cables installed in empty conduits (electrical and network) on the floor.
At the moment, I am quite undecided about the best way to rebuild the floor. Currently, I am leaning towards a dry screed because I will probably also use dry screed in the attic due to the even lower build-up height. But that is another topic. In the basement, I could practice that for the attic.
My plan so far is:
- PE foil
- 20mm (0.8 inches) (bonded?) screed or filling, which would also cover the electrical cables laid on the floor
- 50mm (2 inches) dry screed boards (Fermacell 2*12.5cm (2*5 inches) board with 30mm (1.2 inches) polystyrene rigid foam)
In another thread, I read that I will always have problems with condensation because the floor slab is cold. So how can I best build a proper floor construction? What would you recommend?
My house from the 1960s had a basement party room that was later also used as a bedroom. Now it is going to be converted into an office space. There are two large windows, and heating is provided by a radiator on the wall, so no underfloor heating.
Previously, there was a damaged wooden plank floor. It has been removed, and I have about 7cm (3 inches) plus 1cm (0.4 inches) of new floor covering height available to reach the level of the tiled hallway. There are a few cables installed in empty conduits (electrical and network) on the floor.
At the moment, I am quite undecided about the best way to rebuild the floor. Currently, I am leaning towards a dry screed because I will probably also use dry screed in the attic due to the even lower build-up height. But that is another topic. In the basement, I could practice that for the attic.
My plan so far is:
- PE foil
- 20mm (0.8 inches) (bonded?) screed or filling, which would also cover the electrical cables laid on the floor
- 50mm (2 inches) dry screed boards (Fermacell 2*12.5cm (2*5 inches) board with 30mm (1.2 inches) polystyrene rigid foam)
In another thread, I read that I will always have problems with condensation because the floor slab is cold. So how can I best build a proper floor construction? What would you recommend?
Vicky Pedia16 Apr 2020 22:54Your ideas are actually quite good. The screed doesn’t need to be bonded. For condensation to occur, the water also needs to come from somewhere first. That’s how I would do it. And the dry screed is a good system.
Hello unnamed questioner,
Since this is a ground-contacting slab, "the enemy comes from two sides."
This is actually moisture, on one hand rising from the ground behind and on the other hand possible condensation.
We could counter the first with a sealing layer or a vapor barrier (PE film >0.2mm), but this makes no sense where installation pipes run above the slab.
So, we clean the surface of the slab thoroughly from all dirt particles and level the entire area with a bound screed up to the top edge of the installations.
Bound screeds MUST be used according to the state of the art, which does not necessarily mean that water is involved.
To get to the most important point first:
The build-up height is actually not sufficient to meet the requirements of the energy saving regulation (building permit / planning permission)! For this, a thickness of 100mm (4 inches) (thermal insulation layer) would be necessary. This means: cold feet are also to be expected in winter in the future.
Due to a lack of knowledge about the new surface covering (with 1cm (0.4 inches)), I was unable to calculate exactly if, where, and how much condensation will occur within the floor cross-section.
With a rough calculation, I come to a theoretical value of 0.236kg/m² (0.05 lbs/ft²) of floor area, but this calculation did not take into account that an EPS insulation material (or a PUR rigid foam) is used, which due to its closed-cell structure does not absorb water and must be considered accordingly when evaluating the condensation limit.
As a result, the aforementioned value (condensation) is uncritical if no moisture-sensitive surface covering is installed.
[@ Vicky Pedia] A note that as a layperson you cannot filter out all connections via GOOGLE nor recognize their effects. When a question is asked in this forum, the questioner expects a usable answer. Because he (!) has to face the consequences later, especially those arising from incorrect assessments by others.
----------------------
Wishing you success: KlaRa
Since this is a ground-contacting slab, "the enemy comes from two sides."
This is actually moisture, on one hand rising from the ground behind and on the other hand possible condensation.
We could counter the first with a sealing layer or a vapor barrier (PE film >0.2mm), but this makes no sense where installation pipes run above the slab.
So, we clean the surface of the slab thoroughly from all dirt particles and level the entire area with a bound screed up to the top edge of the installations.
Bound screeds MUST be used according to the state of the art, which does not necessarily mean that water is involved.
To get to the most important point first:
The build-up height is actually not sufficient to meet the requirements of the energy saving regulation (building permit / planning permission)! For this, a thickness of 100mm (4 inches) (thermal insulation layer) would be necessary. This means: cold feet are also to be expected in winter in the future.
Due to a lack of knowledge about the new surface covering (with 1cm (0.4 inches)), I was unable to calculate exactly if, where, and how much condensation will occur within the floor cross-section.
With a rough calculation, I come to a theoretical value of 0.236kg/m² (0.05 lbs/ft²) of floor area, but this calculation did not take into account that an EPS insulation material (or a PUR rigid foam) is used, which due to its closed-cell structure does not absorb water and must be considered accordingly when evaluating the condensation limit.
As a result, the aforementioned value (condensation) is uncritical if no moisture-sensitive surface covering is installed.
[@ Vicky Pedia] A note that as a layperson you cannot filter out all connections via GOOGLE nor recognize their effects. When a question is asked in this forum, the questioner expects a usable answer. Because he (!) has to face the consequences later, especially those arising from incorrect assessments by others.
----------------------
Wishing you success: KlaRa
Thank you @KlaRa.
In summary, this means it should actually be feasible. I should even be able to install the PE foil beneath the pipes.
For the top layer, I roughly estimated 1cm (0.4 inches); it will be a vinyl floor, which is generally considered resistant to moisture.
I understand that I won’t be able to comply with the energy saving regulations (building permit / planning permission requirements), but that’s just how it is in this part of the renovation.
Regarding the condensate: What amount would theoretically still be acceptable? Ubakus mentions 0.5kg/m² (0.1 lb/ft²) within 90 days.
How would it work with proper screed instead of dry screed? Would that be feasible? Which floor structure would you recommend for that option?
In summary, this means it should actually be feasible. I should even be able to install the PE foil beneath the pipes.
For the top layer, I roughly estimated 1cm (0.4 inches); it will be a vinyl floor, which is generally considered resistant to moisture.
I understand that I won’t be able to comply with the energy saving regulations (building permit / planning permission requirements), but that’s just how it is in this part of the renovation.
Regarding the condensate: What amount would theoretically still be acceptable? Ubakus mentions 0.5kg/m² (0.1 lb/ft²) within 90 days.
How would it work with proper screed instead of dry screed? Would that be feasible? Which floor structure would you recommend for that option?
Yes, to summarize: it should be feasible, even if you start having doubts.
You can skip the PE foil on the raw concrete slab! It doesn’t help and only causes a lot of “tedious work” (due to pipe installations), many folds in the foil, and the challenge of not being able to properly seal the overlaps.
Much more important is the thicker PE foil (with 20cm (8 inches) overlap at the seams) above the mineral fill layer! This is also easier to install (since it has already been leveled), and any moisture will not affect the fill layer.
Since the fill layer does not provide thermal insulation, placing the PE foil at this location as I described is perfectly acceptable.
You can’t say that so simply, as this condensate amount assumes it will evaporate again during warmer periods. But at the location you planned, evaporation won’t occur to any significant degree.
My suggestion is to proceed with the build-up as described and additionally include electric underfloor heating. However, this is not possible with a PVC floor glued directly to the screed surface but would be possible with multilayer parquet or other multilayer modular floor coverings installed as floating floors.
With electric underfloor heating, the problem of cold feet in winter would also be solved.
---------------------
You may recognize at this point that flooring technology requires more expertise than what is usually available in public forums?
Good luck: KlaRa
You can skip the PE foil on the raw concrete slab! It doesn’t help and only causes a lot of “tedious work” (due to pipe installations), many folds in the foil, and the challenge of not being able to properly seal the overlaps.
Much more important is the thicker PE foil (with 20cm (8 inches) overlap at the seams) above the mineral fill layer! This is also easier to install (since it has already been leveled), and any moisture will not affect the fill layer.
Since the fill layer does not provide thermal insulation, placing the PE foil at this location as I described is perfectly acceptable.
Tassimat schrieb:
Regarding the condensate: What amount would theoretically still be acceptable? Ubakus says 0.5kg/m² within 90 days.
You can’t say that so simply, as this condensate amount assumes it will evaporate again during warmer periods. But at the location you planned, evaporation won’t occur to any significant degree.
My suggestion is to proceed with the build-up as described and additionally include electric underfloor heating. However, this is not possible with a PVC floor glued directly to the screed surface but would be possible with multilayer parquet or other multilayer modular floor coverings installed as floating floors.
With electric underfloor heating, the problem of cold feet in winter would also be solved.
---------------------
You may recognize at this point that flooring technology requires more expertise than what is usually available in public forums?
Good luck: KlaRa
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