Stairs wrongly concreted, what now? Completion to the upper floor

Hello everyone, we are really starting to despair by now and still haven’t fully paid the construction company, but they are now threatening us. The house is finished by now. Our staircase was supposed to be the showpiece. It is concreted, and we had the covering done ourselves by a well-known carpenter. According to the construction plan, the staircase was supposed to be concreted up to the upper floor. Unfortunately, the last step was "forgotten," and now for the last step we have concrete, styrofoam, screed, and tiles with underfloor heating. The construction company says that was just the way the concreter handled it and that it is okay. Since we wanted to do the staircase covering ourselves, we have to make sure the finish looks nice. We absolutely cannot find a way to make this staircase finish at least somewhat nice, let alone stable. The tile layer from the construction company did not want to help us either because he could never guarantee the finish. What should we do? We want to do the bottom of the staircase with a concrete-look plaster under the steps.

Are the tiles already laid?

mh. I am now on the third house and every staircase has looked basically like yours so far. Solutions were different. For tiled stairs, simply a tile would go in front. For you, 3mm Jakodur or similar and then adjust with concrete filler.

Apart from that, I find the last step to the upper floor very high.

You could also tile the tile 5 mm over the edge and plaster the top riser (with a carrier material) with concrete-look plaster.

The tiles are already laid?

The last 2 tiles on the upper floor are not yet laid so that the finish can be adjusted.

The last step to the upper floor actually matches the other steps. Jakodur holds? In my opinion, the problem is the different wall types for the Jakodur. Movable screed and Styrofoam. When you step on the screed, everything compresses a few millimeters. Nothing will stick to that, right? That’s why, according to the construction plan, there was supposed to be a finishing step made of concrete. So that the wall being covered is immovable. The tiler didn’t want to do it for us because he said it moves too much and he doesn’t give any guarantee for that.

Therefore, my suggestion is to install a rigid, thin plaster base in front of the top riser and to plaster it. Qboard panels, for example, are available in 4 mm thickness. If the floor were to deform so much under pressure load, then the tiles and joints would also crack.