ᐅ Paving stones in garage are sinking under the weight of a car (thermal insulation issue)

Hello community,

I have the following problem: Our paved garage has a basement underneath, which is why there is a bitumen layer under the paving stones and insulation below that. Please don’t judge—using paving stones was not our decision. We bought the house as-is, and unfortunately, the builder no longer exists.

Now, the paving stones are sinking so much under the weight of the car that the bitumen membrane underneath is at risk of developing cracks. We suspect that the insulation material used was too soft.

One option would be to remove everything, replace the insulation with something more “stable,” and/or remove the paving stones and instead pour a monolithic reinforced concrete slab. For understandable reasons, I’d prefer not to do this…

Is it conceivable to place some kind of reinforcement within the gravel/sand base under the paving stones? Something like a grass reinforcement grid, for example. This way, the car’s weight might be distributed better, right? Then the entire substructure could remain untouched, and above all, I could handle it myself. Of course, I realize this is not a proper “standard solution.” I just want it to hold. What are the risks with such a setup? Would such reinforcement ultimately also push through the bitumen membrane?

Thank you very much for your opinion and any ideas.
Elias