ᐅ New cement screed flexes on top of new underfloor heating and insulation

Hello!

We are doing a complete renovation of our ground floor. The house was built in 1921.
Work done so far: Removal of floorboards and clinker slag. The vault was uncovered. On top of that, an insulating concrete/lightweight concrete layer was applied as a height adjustment, thickness between 0 and 20cm (0-8 inches). We allowed it to dry according to the manufacturer’s instructions. The concrete contains many small beads; due to further work and because we continue to live in the house, small indentations have formed along the walking paths in the hallway. All work up to this point was carried out by a construction company. Next, the plumbing contractor installed 4cm (1.5 inches) insulation boards without leveling out the indentations and then installed the hydronic (water-based) underfloor heating. Under the black dimpled membrane, there was another insulation layer; the underfloor heating pipes lie within this membrane. Last Friday, a 5cm (2 inches) cement screed was poured onto the underfloor heating. It couldn’t be thicker due to space constraints. A modifier was added for better hardness and faster drying. Right at the front door, this screed now rocks a few millimeters. The screed is only about 110cm (43 inches) wide there (narrow hallway).

Now the critical question: Who is at fault, and above all, how can this be fixed? Planned (and already purchased for 2500 EUR) are wood-look plank tiles, 120cm (47 inches) long and 20cm (8 inches) wide, for the entire ground floor. This was known to all trades and is especially important to us, particularly in the entrance area. Discussions with the two companies have yet to take place.

My question: Does anyone have suggestions or ideas? Primarily for how to solve this issue. You can cut the screed and remove it at the affected spot, but underneath is the underfloor heating with long pipes running directly to the door. Presumably, you can’t just lift it and level underneath again, since the pipes run through the entire hallway and are all connected. We are now worried this will turn into a bigger problem, where no one wants to take responsibility, and above all, it will cost us a lot of time. We live in the house with our children, and everything was on schedule until now. I estimate this will cost us at least two weeks’ delay, in the best case. The tiler and kitchen installation depend on this, so it’s quite complicated.

Any input would be much appreciated. This issue is keeping us up at night, and nothing will be resolved before the long weekend.

Cement screed tends to bow if it is dried or ventilated too quickly or incorrectly. The subfloor is not at fault in this case. It’s best to check with a long aluminum straightedge to see if the edge area is raised; if so, then the problem is clear.

Besides the complete and unpleasant dismantling, I can imagine the following: locate the underfloor heating, drill between the pipes into the hollow spots, then fill the cavities with a suitable two-component resin or similar material – done.

But of course, this is just my layman’s opinion. More clarity could probably be provided by mEA @KlaRa.

The screed is level and did not get any ventilation for the first 3 days, followed by only occasional airing. We actually moved out over the weekend and therefore didn’t leave anything running.

I spoke with the plumbing company; they want to break open a small section at the front and then fill the cavities with resin. But first, they will come to inspect it next week.

If I remember correctly, each trade is required to check the framework conditions before carrying out their own work. By proceeding, they essentially approve the preceding work. As always, this is just my humble layperson’s opinion. Besides, it is generally better to address such issues openly and without assigning blame to find a solution.

We share this opinion exactly. We sought a direct conversation. As things currently stand, it looks like everything will be resolved well. However, it never hurts to tap into the collective knowledge of a forum. Maybe someone has experienced something similar and can share how the problem was resolved.

We definitely have no interest in alienating the contractors. So far, everything has gone very well — which is definitely worth praising. We have also known one of the companies for quite some time. Of course, we have no interest in any kind of dispute either.