Insulate garage floor

Hello everyone

I have been renovating the wooden carport over the past few years. It was fully lined with wood, and I insulated the ceiling with 60mm PUR XLS. Additionally, there is an electric gate.

The point of this nonsense: I am a passionate car mechanic and need a warm garage. The price I pay for that is that I have to dehumidify. I do that and it doesn't bother me.

The floor consists of 20x20 drainage stones, above that is a rubber mat and above that cardboard. Below the drainage stones is about 10cm of gravel and beneath that only good old mother earth.

Heating works. However, I notice that most of the heat is lost through the floor. While the infrared thermometer shows relatively good results on the walls, the floor only reaches about 5-7°C at a room temperature of 20°C.

I would also like to insulate the floor in spring. Question: remove drainage stones, remove gravel, lay 40mm PUR mats, gravel on top, drainage stones on top.

Will that work, or will it be a no-go?

Regards, Philipp

The technical data of XPS insulation allows a pressure of 30t/m². However, since you want to lay permeable stones, the pressure per stone would be much higher (I have not calculated this now, but with the same load, the pressure increases immensely as the loaded area decreases). The permeable stones do not technically/physically form a load-distributing surface, but rather small individual surfaces per stone. If you were to pour a concrete base slab, your idea could be implemented more easily, as you would then have a load-distributing surface. My suggestion: Get advice from a manufacturer of XPS insulation materials; this can be done by phone, and sometimes a consultant comes on site - that would be the safest.