Hello dear forum community,
I am about to purchase a semi-detached house (built in 1928) and am currently dealing with various renovation and modernization issues. The house will receive cavity wall insulation (8cm (3 inches)) and insulation for the basement ceiling (20cm (8 inches)). Additionally, a heat pump will be installed. At the moment, there are quite different radiators installed — from old cast iron radiators to mid-aged and modern ones. All of these will be removed and replaced with underfloor heating.
So far, I am planning to use the dry screed system from Selfio, as I don’t want to add too much weight to the wooden beam ceilings (on all floors) and I think it will be easier than pouring the screed myself.
What are the requirements regarding the flatness of the substrate before installing the system panels? Should I sand the plank floor beforehand to create a flat surface? Or will any height differences be sufficiently compensated by the polystyrene system panels, the dry screed, and the floor covering (probably parquet: glued or floating)?
Many thanks for any experience, assessments, and tips!
I am about to purchase a semi-detached house (built in 1928) and am currently dealing with various renovation and modernization issues. The house will receive cavity wall insulation (8cm (3 inches)) and insulation for the basement ceiling (20cm (8 inches)). Additionally, a heat pump will be installed. At the moment, there are quite different radiators installed — from old cast iron radiators to mid-aged and modern ones. All of these will be removed and replaced with underfloor heating.
So far, I am planning to use the dry screed system from Selfio, as I don’t want to add too much weight to the wooden beam ceilings (on all floors) and I think it will be easier than pouring the screed myself.
What are the requirements regarding the flatness of the substrate before installing the system panels? Should I sand the plank floor beforehand to create a flat surface? Or will any height differences be sufficiently compensated by the polystyrene system panels, the dry screed, and the floor covering (probably parquet: glued or floating)?
Many thanks for any experience, assessments, and tips!
Hi,
you’re definitely on the right track by not just laying the dry screed system directly on the floorboards without preparation. The flatness requirements for underfloor heating are significant since unevenness will be clearly felt later—and neither parquet nor tiles will forgive or compensate for that. The polystyrene elements can level out minor unevenness, but not more than about 3-4 millimeters (1/8–3/16 inch). If your floorboards look like an Alpine panorama, you will likely face hollow spots around the edges of the system panels and the dry screed elements.
Depending on the condition of the existing floor, it might make sense to sand down major unevenness, but more often leveling or straightening is done using leveling compound, dry screed leveling granulate, or even spot repairs by refastening or replacing “wandering” boards. Also pay attention to typical noise bridges caused by floorboards that are insufficiently decoupled.
Floating parquet on dry screed is possible, but with underfloor heating I would actually prefer gluing over floating because a) it minimizes thermal resistance and b) reduces clattering underfoot. I always wonder, though, why floating floors are so popular in old houses with wooden beam ceilings—it’s like a double flexibility buffer, but without damping.
Good luck!
you’re definitely on the right track by not just laying the dry screed system directly on the floorboards without preparation. The flatness requirements for underfloor heating are significant since unevenness will be clearly felt later—and neither parquet nor tiles will forgive or compensate for that. The polystyrene elements can level out minor unevenness, but not more than about 3-4 millimeters (1/8–3/16 inch). If your floorboards look like an Alpine panorama, you will likely face hollow spots around the edges of the system panels and the dry screed elements.
Depending on the condition of the existing floor, it might make sense to sand down major unevenness, but more often leveling or straightening is done using leveling compound, dry screed leveling granulate, or even spot repairs by refastening or replacing “wandering” boards. Also pay attention to typical noise bridges caused by floorboards that are insufficiently decoupled.
Floating parquet on dry screed is possible, but with underfloor heating I would actually prefer gluing over floating because a) it minimizes thermal resistance and b) reduces clattering underfoot. I always wonder, though, why floating floors are so popular in old houses with wooden beam ceilings—it’s like a double flexibility buffer, but without damping.
Good luck!
Thanks for the detailed response 🙂
I think after removing the current floor covering, I’ll spend some time checking the subfloor and, if necessary, sanding it. I’d prefer to avoid adding an extra screed or self-leveling compound: height buildup and application (with the self-leveling compound, I would need to install formwork at the stair landing and in the stairwell, the joints in the plank floor need to be properly sealed, and so on).
I had already thought that gluing the floor might be the smarter choice—although I’ve never done it before, it shouldn’t be too complicated with proper guidance and preparation. I would love to install a herringbone pattern, but trying that without experience could backfire.
I think after removing the current floor covering, I’ll spend some time checking the subfloor and, if necessary, sanding it. I’d prefer to avoid adding an extra screed or self-leveling compound: height buildup and application (with the self-leveling compound, I would need to install formwork at the stair landing and in the stairwell, the joints in the plank floor need to be properly sealed, and so on).
I had already thought that gluing the floor might be the smarter choice—although I’ve never done it before, it shouldn’t be too complicated with proper guidance and preparation. I would love to install a herringbone pattern, but trying that without experience could backfire.
Now the time has come. I have removed up to seven layers of flooring in some areas (laminate, particleboard, hardwood, carpet, etc.) and found that the floorboards are mostly in poor condition. There are many splinters and tears, significant height differences (under the previous screed), and considerable mold. Therefore, these boards will be removed and the floor rebuilt on the joist structure.
My plan is to install a layer of OSB, then the underfloor heating (as described above), followed by glued hardwood flooring, and tiles in the entrance and wet areas. Before installing the OSB panels, the joist structure will be checked for levelness. If necessary, battens screwed to the sides of the joists will be used to create a flat base.
Questions
My plan is to install a layer of OSB, then the underfloor heating (as described above), followed by glued hardwood flooring, and tiles in the entrance and wet areas. Before installing the OSB panels, the joist structure will be checked for levelness. If necessary, battens screwed to the sides of the joists will be used to create a flat base.
Questions
- What thickness should I choose for the OSB panels? I often read about 25mm (1 inch), but I wonder if the buildup with the underfloor heating and the dry screed might add enough stiffness to make 18mm (3/4 inch) sufficient.
- If needed, what thickness should the battens screwed to the sides of the joists have to create a level base for the OSB layer?
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