New construction - Using the attic as living space - Increased costs

Hello,

we have purchased a small urban plot (400m²) and are planning to build a single-family house. Since the development plan allows it and we want to have as much garden as possible, we plan to build on 2.5 floors (2 full floors and 1 study in the attic). However, our architect has clearly advised us to only build 2 full floors because the costs in the attic would explode. Several construction companies, however, have a completely different opinion.

Since the study (where we would spend a lot of time professionally and which also does not allow us to place it on the ground floor, and that would come much closer to our desire for a large living area) in the attic is very important to us, I just wanted to ask again what you think about it.

After all, we want to later invite different construction companies to tender and therefore take their opinion regarding the costs seriously, not just that of the architect.

Thank you very much

However, our architect has clearly advised us to stick to only 2 full floors, as the costs would explode in the attic.

The question is what the architect means by that.

1. You manage with the planned living space in the full floors (then somewhat smaller rooms), then the finished attic including roof insulation would be many times more expensive than the cold roof, where the insulation is done on the top floor ceiling.
2. You need the living space in the full floors and the study would be additional. Then the ground floor layout might be completely messed up. The upper floor layout anyway (it would also become larger). I even see finishing the attic as a cheaper option than redesigning and enlarging the ground floor by, for example, 12 sqm, which at the same time leads to an enlargement of 12 sqm in the (newly planned) upper floor.

we plan to go with 2.5 floors (2 full floors and 1 study room in the attic).

I am always a fan of expanding the roof - at least in the planning stage and later implementation in EL, for… yes, exactly for the reasons you mention.
Often the planned or feasible floor area on the ground floor is not enough for everything. And if you can plan upwards, meaning a somewhat steeper roof with a fixed staircase, then you can also use the already existing space under the roof.
Yes, insulation and stairs are additional costs.
Electrical cables going up, too. But you can do the rest later (yourself) (or have it done).
It is cheaper than letting the house grow in floor area.
Pay attention to windows in the gable (second escape route, then there is nothing preventing rooms upstairs from being used as living spaces.

Do the builders know the floor plan? Can the staircase simply be extended into the attic or do you need a dormer for that, or do you have to completely redesign the floor plan? Basically, it is also a great advantage to be able to reach the attic via a normal staircase instead of only a retractable ladder.

Basically, I mean of course the cost comparison, where I compare apples to apples and the room in the attic does not become additional living space.
So, for example, my 2 single-family houses with once 75 m² and 75 m² = 150 m² and once for example 67 m², 67 m² and 16 m² (DG) = 150 m².
How much more is it here (even if of course you can't say that). But is it rather in the range of €5,000 or €20,000 or €50,000?
No, the construction companies do not know the floor plan because there is no fixed floor plan yet.
But in any case, the attic should be reached by a normal staircase (but already space-saving).

How much more is it here (even if you obviously can’t say for sure). But is it rather in the direction of €5,000 or €20,000 or €50,000?

At first, I don’t see any additional cost in your example at all. Maybe (depending on the house architecture, etc.) it will even be cheaper.

Although the attic room has 16 sqm, the floor area will be significantly larger (because of the sloping roof). So disproportionately much floor space, etc. in relation to the living area. Maybe that’s what the architect means?

What costs has the architect calculated? How far along are you anyway, you’re talking about two different houses with different floor plans.

P.S. By the way, I find your example dumb. You have to calculate what 1.) a 2x67 sqm house plus unfinished attic costs compared to 2.) a 2x67 sqm house with finished attic. And then 3.) put the 2x75 sqm house plus unfinished attic against them. When you read these lines, you will notice that house 1 compared to house 3 will already have a significant price difference (around €40,000-50,000?). Can you finish your 16 sqm in the attic with this price difference? I would bet my bottom bottom on it ;-)