I was thinking of lowering the floor joists in the future bathroom a bit to make room for water-based underfloor heating (12 mm?), leveling compound, slope, and tiles without creating any noticeable height difference compared to the floor outside.
Is 50 mm enough to achieve a proper slope from the shower floor drain and a thick enough layer of leveling compound at the thinnest point to ensure the right stiffness? It is a wooden beam structure that I plan to cover with a layer of screw-glued flooring chipboard and then level.
Stuck with 40 mm, the underfloor heating pipe doesn't fit well closest to the floor drain, does it? I assume you need a few mm over the pipe depending on the type of leveling compound and substrate?
Ok. If you aim for the lower part of the range GVK stipulates for floor slope, you can manage with 30 mm. But there is a greater risk of backfall. I think I'll go for 50 mm. The floor joists are currently on the foundation wall, and I don't want to notch them too much. It doesn't matter if the floor is 10 mm higher than outside.
