Insulated floor garden shed with paving slabs?

Hello,

we have a brick garden shed that stands on a concrete foundation. A solid fuel burner along with a pulverizer is to be installed in it. Accordingly, everything will be insulated. I would like to insulate the floor in a simple way and had the following idea:

1. Construction foil

2. On top of that 5 cm screed polystyrene

3. On top of that 2 cm tongue and groove OSB boards

4. On top of that 5 cm concrete paving slabs glued and grouted

With a 12 cm build-up, I have leveled the previous step to the door that had also annoyed me.

My idea was to solve the whole thing in basically one step with the concrete paving slabs instead of a concrete screed with subsequent tiling.

It should be functional and cost-effective with the premise that it carries the approximately 350 kg heavy wood gasifier as well as the 800 liter buffer tank.

My biggest concern is the point load. The screed polystyrene is walkable and comes from the renovation of our house, where it was under the screed.

As mentioned, the heating and buffer tank are heavy.

Would you resort to a different insulation here instead of the screed polystyrene?

Which adhesive would you recommend to glue the 60 x 30 x 5 cm paving slabs to the OSB boards?

How much expansion joint would you leave all around?

Thank you very much for your assessment

Would you use a different insulation here instead of the screed Styrofoam?

Make a composite screed below the two heavy parts. Insulate the rest properly - regardless of the construction (maybe PUR instead of Styrofoam). 5cm Styrofoam provides very little insulation. Instead of OSB/concrete boards, you could also work with dry screed boards.

I would rather use tank platforms, which are available ready-made in various sizes, with PU core insulation integrated, steel sheet on top, approved exactly for such point load cases.