ᐅ Expandable attic in a new build: what are the options for future development?

Hello everyone,

We are building a semi-detached house with 2.5 floors and have now planned the layout so that everything fits on 2 floors. However, we still want to keep the expansion option in the attic (originally, the entire attic was planned to be finished).

We are building with a prefab house company, meaning timber frame construction. If we only finish the attic in 5+ years, we don't really want to commit to a future floor plan now; we want to keep all options open. We are building to KfW 40 standard with a heat pump, underfloor heating, and a central ventilation system.

• According to the builder, the ventilation and heat pump will be sized larger to cover the future living space as well. At the same time, the pipes for this will already be installed to the attic. Conduits for electrical wiring will also be laid.
• We would also have the staircase to the attic built now, including the wall and door between the stairwell and the attic.
• The attic is insulated as well.

To save as much as possible, I was thinking of leaving out the following:

• Knee walls
• Walls (to keep freedom in the room layout later)
• Roof windows (one standard window will remain)
• Pipes for underfloor heating
• Screed
• Possibly drywall or paneling in the attic

What do you think? Does this make sense? Are we leaving out too much? The builder says we should definitely include the screed (which is the biggest cost with underfloor heating) because otherwise it will just be a mess later—but is that true? What about dry screed or liquid screed applied in the attic later? Does that cause problems with drying in an already occupied house? Is dry screed worse? Are there differences with underfloor heating if I have liquid screed downstairs and dry screed in the attic?

Since I lack expertise in this area, I would really appreciate your informed opinions: Is the builder just trying to make more money, or would it actually be better to have almost everything finished from the start?

Many thanks in advance for your answers!

philipp013 schrieb:

Since I lack the technical knowledge on this topic, I would really appreciate your expert opinions:

But only if you participate more actively than in https://www.hausbau-forum.de/threads/grundrissplanung-doppelhaushaelfte-fuer-1-familie-4-personen-auf-kleinem-grundstueck.47858/ (otherwise, for now, I will limit myself to the comment that the planned approach here is nonsense).
And I would like to remind you of the follow-up question

hanghaus2023 schrieb:

Does the builder of the other semi-detached house already exist?

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11ant schrieb:

But only if you get more involved than you did in https://www.hausbau-forum.de/threads/grundrissplanung-doppelhaushaelfte-fuer-1-familie-4-personen-auf-kleinem-grundstueck.47858/

Thanks for the reminder, I had completely forgotten that thread (and apparently didn’t subscribe to any notifications).

11ant schrieb:

the planned approach here is nonsense

I’m curious about the reasoning, since my planner hasn’t really given feedback, I’d be very grateful for it.

The other semi-detached plot has recently been sold..

Is dry screed actually suitable for underfloor heating? It’s basically just improved gypsum boards. However, site-mixed wet screed (i.e., in the roof) is possible. I would also have the sloping ceilings boarded to protect the vapor barrier foil.

Grundaus schrieb:

Is dry screed actually suitable for underfloor heating? Those are basically just improved gypsum boards. However, site-mixed wet screed (i.e., in the attic) is possible.
I would also have the sloped roof surfaces boarded to protect the vapor barrier.

Thank you, does this then pose a potential moisture issue while the screed is drying?

11ant schrieb:

I consider your other thread obsolete to some extent, as I do not see any "housing need only starting in five years" here at all.

That is why I am currently not spending any time responding to this (in my opinion, follow-up question) thread.

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