Is tile over tile sensible with underfloor heating?

Good day,

we have the opportunity to buy a house.
There is underfloor heating installed on the ground floor, but with old and not so "nice" tiles.
We would like to replace these.
What is the most sensible option now? Remove the old tiles or lay tiles over tiles?
We would definitely prefer the second option. Has anyone done this at home?
Is the heat still distributed well?

Further info: - The build-up height is not decisive, since we would replace the doors.
- Our desired tiles measure 600x300x10mm

I would appreciate some advice.
Thank you

then it would be colder on the feet. the further tile insulates rather

What is the most sensible option now? Remove the old tiles or lay tiles over tiles?

In my opinion, the most sensible thing is to remove the old ones and then lay the new ones. That's what I did myself. What else would you do if something needs to be redone in 20 years? I also don't approve of simply wallpapering over old wallpaper. That just postpones the problem into the future. So it's better to do it properly right away. With underfloor heating, laying tiles over tiles would probably make the heating slower because there is more mass to heat up. In my opinion, that can only be a last resort.

Hello "thesit27". Every building material has a so-called thermal resistance. We are talking here about a warm water underfloor heating system and ceramic tiles. With increasing material thickness (of the tiles + tile adhesive), this thermal resistance increases. Depending on whether the underfloor heating was designed "at the limit" or not, doubling up with a second tile layer can lead to the rooms no longer being adequately heated. Doubling up is therefore risky, I would not recommend it. I suggest the following solution: Sand the old tile layer with a diamond blade, vacuum it, prime it and plaster it at least 2mm thick. A load-distributing fabric made of glass fiber is embedded into the still not fully cured plaster material, integrated into the plaster with a spiked roller and plastered over again. This construction prevents the joint patterns of the old tile layer from showing through the top covering later. After sanding again (the cured plaster), have a design flooring fully bonded in adhesive method laid. Design flooring means PVC planks with realistic wood or stone decors. This results in a reduced build-up height of approx. 7mm. For a 10mm thick ceramic tile, 10mm, approx. 2mm must be added for the adhesive bed, so we come to a total build-up height of approx. 12mm. ---------------- Another solution (without removing the old tiles) would be to grind the old tiles with a diamond blade, vacuum, and apply a scratch plaster over the joints using a reactive resin mortar. Then prime the entire surface with an EP resin, while still in the wet phase sprinkle with furnace-dried quartz sand 03/1.2mm, let cure, sweep off excess sand, briefly "clean sand" with a rotary sander, vacuum, plaster 2mm thick and then glue a PVC design flooring onto this. With this variant, we come to a build-up height of about 4-6mm. The necessary heat transfer would definitely be ensured this way. ---------------------- Good luck with the measure: KlaRa

Are you sure that the proposed construction with [Designboden] has a lower resistance than 2 layers of tiles? According to my table, tiles are six times lower than vinyl flooring.

@ "77.willo": 1. There is no DEN thermal resistance and 2. the total thermal resistance depends on the material-specific thermal conductivity coefficient and the thickness of the material as well as transition resistances between different layer sequences (and we have those in this case). The subject of heat transfer in connection with the energy yield for heating a room is highly complex and cannot or should not be reduced to empirical data (of the thermal resistance). Because in the end, the questioner pays the price (figuratively speaking) for an incorrectly dimensioned floor structure based on a legally non-binding statement in a public forum. My statements, as outlined above, are technically sound (since they concern my area of expertise) and at least guide the questioner in the right direction. However, the decision always remains with them. ------------------ Regards: KlaRa