ᐅ Is a screed necessary? Unfinished but insulated attic space

Hello community,

We are currently planning a semi-detached house with a developer and I need some advice on one question.
It’s about the attic, which is not living space and not heated, but will be used for storage.
The roof will be insulated with 240mm (9.4 inches) of mineral wool and OSB boards, and the floor consists of a 20mm (0.8 inches) concrete slab.

My question: Is it necessary to seal the floor with screed, or can this be omitted for a purely storage area? The costs seem relatively high, so I’m asking about the benefit.
According to the developer, the screed would of course contribute to thermal insulation; without screed, the upper floor would help heat the attic. But since I have insulated the roof, no heat should be lost.
Is it possible to estimate how many degrees the attic would heat up more without screed compared to with screed?
Is it really necessary to install screed, or would floor coverings be sufficient? I just want to store cabinets and boxes there.

Thank you very much for your help and support,
Best regards
Holleradhiho

Normally, the ceiling on the upper floor is insulated, and the attic remains uninsulated... at least that's how I know it... and a screed in the attic is new to me as well...

What kind of roof do you have, and what is the height of the attic? Is it accessible by a regular staircase or only by a retractable attic ladder?

An uninsulated attic was included in the standard offer, but since I plan to use it, we agreed to insulate the roof.
The attic is accessible with a retractable ladder, and in the gable area there is a clear height of 2.3m (7 ft 7 in), with a roof pitch of 30°.

Is a screed floor necessary in this case?
As mentioned, the builder refers to thermal insulation effects, as otherwise the attic would be heated through the upper floor. Should this be avoided, or is it negligible?

No screed necessary. Why use a concrete ceiling at all if it’s only going to be used for storage? Properly thick OSB/particle boards are sufficient.

However, to avoid heating the entire attic space, I would also insulate the ceiling of the top floor. It’s not a big cost or time investment and can easily be done yourself with insulation batts (stone wool or glass wool).

The concrete ceiling is part of the building structure, and I won’t be able or willing to change that.

readytorumble schrieb:
insulate the attic ceiling as well

I don’t quite understand this now:
1) The upper floor ceiling is a reinforced concrete slab, wallpapered with fiberglass fleece.
2) Above that is the attic; the roof is insulated, but the attic floor is bare.

Should I insulate the upper floor ceiling now? After it has been wallpapered?
That means the heat transfer from the upper floor to the attic through the concrete ceiling is not negligible, and something should be done about it, am I understanding this correctly?

Is the attic also located within the airtight building envelope?