Tiles come loose after 36 years with a noise

Hello everyone I registered on this forum because I am faced with a puzzle. Maybe someone knows this?

A few days ago I heard a loud cracking and crackling like from a large wood fire. The cause were the tiles which bulged up to 3cm due to high compressive stresses. The installation was 36 years ago, no water - the cement screed is absolutely dry and still level.
What could be the cause?

I wish you all a nice summer weekend.
Gluehstrumpf2

What could be the cause?

You write it yourself: the compressive stresses. How much pressure do you have now in the tileless cabin? Show a photo of the wall with the extent of the damage.

Hi Gluehstrumpf,

from your description it is noticeable that the screed has remained level according to your own statement. Tiles rarely crack in this way without external influence. Sometimes years-old coverings are simply overloaded due to gradual material fatigue, but also due to omitted movement joints or thermal stress. It would be interesting to know whether similar phenomena occur in other adjacent rooms with less light exposure.

Good luck!

That strongly sounds like so-called tenting in tiles, caused by stresses that have built up over years. Common causes are missing or hardened expansion joints, tiles fully trapped between baseboards/walls, or joint material that does not allow movement. With temperature and humidity fluctuations, the covering expands minimally but cannot relax; eventually, this tension releases suddenly, and the tiles warp. Adhesive and grout can also lose their elasticity over time, which intensifies the effect.