Which expansion stage for the attic as an expansion reserve?

Hello everyone,

we are currently in initial talks with providers for a new single-family house with a pitched roof. The attic should be planned as a reserve for expansion while the children are still small and used until then as storage space, playground, and cellar replacement.

Unfortunately, everyone says something different regarding the "expansion stage" that should be initially commissioned so that a possible expansion does not mean too much intervention. The house is planned with underfloor heating and district heating on the ground floor.

What would you advise to include in a house build with a general contractor to be able to "use" it in the rough state as described above?

[*]Insulation of the concrete ceiling or roof insulation?
[*]Have the screed laid immediately?
[*]Does it possibly also make sense to completely do without underfloor heating in the attic (because room planning is still unknown) and have a screed laid right away?
[*]Should windows already be provided or keep everything "closed"?
[*]Have lines prepared and run upwards?
[*]Plaster the attic walls?
[*]etc.

It would be great if someone had a few tips and experiences on hand regarding which combination makes sense here.

Thanks and best regards

Experience values would be great

Insulating the ceiling instead of the roof is possible, but it costs money for the appropriate insulation material (walkable) and flooring. If you insulate the roof directly, you should also heat it and consequently have underfloor heating and screed installed at the same time.

Screed would be necessary for underfloor heating anyway. Having it installed without underfloor heating means later having to overhaul the heating concept or break out the screed again.

Windows in the masonry should at least already be planned. Subsequently bricking up these openings instead of installing a window directly does not offer any significant savings potential. The only thing you could initially do without are double-leaf windows and simply provide a few openings in the appropriate places.

You should definitely have the wiring installed at the same time; after all, it costs almost nothing and at least electricity is needed up there anyway.

Plastering the walls depends again on the interior finishing. If there's already screed with flooring installed, you won't want a plasterer coming in later. But even here, I see at best a saving potential of a few hundred euros on the few square meters of gable masonry.

In short: If it is already certain that the rooms will be needed later: Definitely do it all at once – not least because they will then already be approved. The 2-3k you could currently "save" does not justify the trouble.

I would definitely plan out where each room could be located. It's not just about electricity but also about water and sewage if you are planning a toilet or bathroom. Additionally, things like [SAT] or network should not be forgotten either.

If it is already certain that the rooms will be used in the future, then have it done right away.

Thank you very much for the input.

We will probably now only have the screed laid to have a proper floor and insulate the ceiling below it. However, we will not insulate the roof. Connections will be raised. If we ever want to properly expand at some point, a few normal radiators will have to do.

Windows in the exterior walls are planned. However, the WC or bathroom is definitely not to be expanded in the attic. Basically just storage or hobby rooms.

You can also deal with a heating system over the wall surface, basically underfloor heating for the walls, and it doesn't require any floor construction.