Insulation of the top floor ceiling (cold attic)

Hello everyone,

slowly the construction is taking shape and the upper floor is completely finished. Now it’s time for the insulation of the top floor ceiling.

The attic is only intended to be used as storage and will not be heated or insulated.

The plan is now to build a row of stones (25cm high) onto the floor slab, line the inside with 2x 10 cm 035 Styrofoam, and then pour a 5 cm screed layer on top.

Is this material the right choice or are there big differences?

The roof truss itself will then be covered with 18mm boards and sealed with foil.

Are there any other ideas?

Thank you very much

The attic is only to be used as storage and is not to be heated or insulated.

What material is the top floor ceiling made of (ceiling construction)?

The attic is only to be used as storage

Regularly accessible or only sporadically?

The plan is now to lay a row of bricks (25 cm high) on the floor ceiling, line the interior with 2x 10 cm 035 Styrofoam, and then pour a 5 cm clean layer of concrete on top.

That would be too complicated for me.

Rafters in cold roofs must remain open, no foil on them,
the underlay of the roofing must even be opened in some places for ventilation, otherwise you are building a dripstone cave with all the late consequences
Regards Nida

Thank you very much. Yes, I need to talk to the carpenter again. Moisture would of course be fatal. My main concern is the insulation structure. Is that feasible?

the top floor ceiling is a 24 cm concrete slab. The room is only used as storage; it is checked every few weeks. The reason for the 5 cm concrete layer is to add more mass to the ceiling to keep the heat out.

So basically encasing Styrofoam in concrete? No way! There are walkable precast elements. Just lay them down and that's it. Or is it the financial issue?