Ceiling construction on the upper floor - concrete or wooden beams?

Hello everyone,

our builder advised us to construct the ceiling above the upper floor as a concrete ceiling (we are building a city villa with a hipped roof). The space above the upper floor will not be used by us, but should contain a retractable ladder so that we can easily access it anytime. Above the concrete ceiling, Styrofoam should be laid as insulation.

What do you think of this approach compared to the wooden beam construction? Are there only advantages here (e.g., thermal insulation) or should one avoid this?

First of all, the concrete ceiling has a consequence for the upper floor, namely the requirement for load-bearing walls. These, in turn, either need load-bearing walls beneath them as well or additional structural effort compared to the possibility of settling for lightweight walls on the upper floor. In the classic Neo-town villa aka substitute villa, one usually builds a hipped roof / hip roof as a truss roof with the main function of a "lid." Your builder's proposal (I suspect the term BT is here, as "usual," misused) suggests that in your case a rafter roof is planned. Then a concrete ceiling is the better basis for the then classic roof structure. The question of a cold or warm roof is only of secondary relevance.

How much extra does that cost? For me, it would have been 13xxx EUR, which is why I decided against it. One advantage would certainly be that you can also store heavier things there. My studio binder roof now has a load capacity of 80 kg per m², which basically means I technically shouldn’t be up there, but it’s probably more about long-term stress. I guess the sound insulation would also be better. Concrete alone doesn’t offer outstanding thermal insulation values, but it stores heat quite well, so in summer without insulation it’s even disadvantageous. So insulation has to be added anyway, which your BU also told you. So if he does it at no extra cost or for a small surcharge, I would do it, as it simply makes the use of the roof structure more flexible.

we also have a concrete ceiling combined with a cold roof. Simply lay polystyrene insulation on the ceiling, chipboard on top for walking on, and the storage paradise is ready

We also have a concrete ceiling with 20 cm of styrofoam insulation and 5 cm of protective screed on top. According to the builder, this keeps the heat out better in summer than a pure wooden roof truss. Another advantage is that the concrete neatly fills every gap and does not need to be cut extensively. It is a clean solution and the attic can be used well for storage.

If there is no big difference in price, I would choose concrete. There is also less movement between the wall and ceiling compared to wood.