Which flooring is suitable for underfloor heating?

I can say something about the topic of cork :-) We have glued cork in the bedrooms and children's rooms (entire upper floor, without bathroom).

For this, we glued cork tiles 4mm thick from KWG in the size 30x60 directly onto the screed. We chose 4 mm because we renovated and the build-up height fit perfectly with the stairs. Although 6mm would have also worked in hindsight.

Even though 4mm is quite thin, the walking feel is great. The floor is pleasantly soft and nicely warm. Additionally, absolutely quiet. You don’t hear anything. Especially in the children's room where there is a lot of running around, I find the floor (for us) perfect. The child lounges on the floor and it is always nicely warm.

We actually oiled the surface according to the manufacturer’s instructions and are satisfied with it so far. Oiling gave a nice rich color tone and it feels great. Important with cork, it will fade over time, which doesn’t bother us right now, especially in the upper rooms.

We have a dog in the family, but he doesn’t live with us permanently (however that sounds :D). I don’t know how the floor would react to constant drooling. But as long as he only sleeps upstairs, I wouldn’t have any concerns with oiled cork.

Cork is particularly environmentally friendly :D *clap-clap*

;)

One disadvantage is that cork lasts less long than many other mentioned materials and that it insulates, but the mentioned advantages are unmatched by anything else: very quiet and very pleasant to walk on

I would have gone with cork immediately if the look weren't so strange.

I would have gone with cork right away if the look wasn’t so strange.

That’s true. The look is not for everyone. For us, it was clear: if cork, then also the cork look. We didn’t choose the very fine sorting, but with larger pieces. Big love here with us :-)

Just saw that there are also some with a wood look (probably excluded back then due to the price) costing from 29.99 per m². So still within the range for the OP. Then I shift my recommendation to cork flooring! Check out Wicanders wood START Green Design. It is apparently also installable as a floating floor with a click system. Whether it is still so very soundproof, I don't know. But you can order a package as a sample and let the dog walk over it... :D

Yes, rigid vinyl is also an option. If vinyl is the better choice for us, I wanted to see which vinyl is best: regular with impact sound insulation or the rigid vinyl. The impact sound insulation can possibly compensate for unevenness in the screed (dents or pimples) better than the rigid, right?

Yes, of course the impact sound insulation can compensate for that better. I will also put one underneath, although I could leave it out.