Cracks in old screed (including underfloor heating)

Hello everyone,

Our screed (with underfloor heating) from 1979 has cracks. Previously, tiles were glued on. We would like to glue parquet and wonder if the cracks need to be closed beforehand. The cracks run across the entire screed each time, always from wall to wall. Can this be assessed from a distance?

Usually, such cracks are resin-filled. For this, a depot groove with cross grooves is milled along the crack. Connectors are placed in the longitudinal groove in the cross groove along with the resin. Caution! Mill with a depth stop to avoid hitting the heating pipes. There are many explanatory videos in the media where products are also named. If you do not feel confident doing this, please have it done by someone else!!!!

Thanks for your feedback. I should be able to manage that myself. What would actually be the theoretical consequences if you don't do this? The tiles beforehand actually looked quite good.

Oh God, pure theory. Nothing happens because it has long since settled or, in the worst case, it damages the underfloor heating. I won’t commit to this from afar. The fact is that the screed is no longer a homogeneous surface and the individual slabs can move. The tiles obviously bridged the cracks effectively. Officially, I can only advise you to resin ... Everything else would be speculation.

Hello and sorry for jumping into the thread, but I am stuck on the same question. Therefore, a quick follow-up. Do I (should I) also resin the cracks if I lay a decoupling mat over the screed?
Thank you very much and best regards, Sven

Before retiling, full-surface uncoupling mats (if I remember correctly, from Sopro) were applied, no resin was used (the cracks were also very narrow). The screed was also from 1979/80 with underfloor heating. Often, the pipes of the underfloor heating are the problem with that construction year because they are not oxygen-tight. Either these should be replaced in case of problems (corrosion damage caused by oxygen ingress through the pipes) or the system should be flushed and separated from the rest of the heating system with a heat exchanger.