I have the following problem: our paved garage has a basement, so there is a layer of bitumen under the pavers and thermal insulation underneath.
Now the paving has sagged so much due to the car that the bitumen pad underneath is in danger of cracking. We suspect that too soft a material was chosen for the insulation.
One option would be to tear everything down, update the insulation and make it more "stable" and/or remove the pavers and instead make a floor slab of one poured concrete with reinforcement. But that's very costly and expensive.
Is it possible to put some kind of reinforcement in the rubble under the paving stones? For example, something similar to grass mesh. Then the weight of the car would be distributed a little better, wouldn't it? Then the whole substructure could also remain intact, and most importantly, I could do everything myself. I realize, of course, that this is not really a "standard solution." I just want it to last a long time. Where is the danger in such a design? Will such rebar eventually push through a layer of bitumen?
The idea of spreading the weight of vehicles over a larger area is a good idea. Remove the paving stones, install a large area steel slab, install the paving stones again – it should last a long time. Alternatively, if you don't want to keep the pavement, you could work with some kind of beam layer.
I would give up the insulation completely. I wouldn't be surprised if the salt water degraded the insulation.
Styrofoam insulation and then sheets of bitumen welded as a barrier. For a garage? As a patio it would work. But 2 tons on it (4 tires) would not work. Anything other than new construction would be unsatisfactory.
I would completely deconstruct. The ceiling to the basement should be airtight. A reasonable polystyrene, waterproofing and a floor slab on top. Then it will hold up.