ᐅ Ground Floor Extension vs. Upper Floor Roof Structure Extension – Which Is More Expensive?

Here are the current floor plans with a bit of explanation 🙂

On the ground floor, at the very back of the drawing, basically where the wing piano is located, is the extension.
This part needs to be covered on the upper floor.

Alternatively, we want to build a side extension on the right side of the house, starting from the front window at the bottom right up to the old extension.

Is this clearer this way?

I can imagine that extending the attic will be more cost-effective. An extension requires a concrete slab foundation, etc.
Besides, don't you need more space on the upper floor?

@ Schnuck

Thanks so far. Does the single-family house have a basement?


Bauexperte

@Bauexperte: Yes, there is a partial basement in the front area. The basement dates back to 1948, so it is not suitable as living space.

@ypg: We don't really mind where the living space is created – it just needs to have more space for children's rooms 🙂

Good morning,

Schnuck schrieb:
@Bauexperte: Yes, the front part of the house has a partial basement. The basement dates back to 1948 and is therefore not suitable for living space.

Well then...

If you build an extension on the side, you will need to support the existing house in the area of the partial basement; an extension would only make sense as additional living space for the kids if it is built over both floors. In the case of a side extension, this would require a partial reconstruction of the existing roof. The current 2.00 m (6 ft 7 in) line is quite far inside, which means the extension should have a minimum finished interior depth of 2.00 m (6 ft 7 in) in order to significantly benefit the children's rooms. For this side extension, costs will arise for supporting measures for the existing single-family house, as well as for the foundation slab, masonry, windows on the ground floor and upper floor, roof connection, and extension; of course, plus the costs of interior finishing.

If you want to continue the existing extension into the upper floor, the roof must also be partially removed to create a concealed connection later on. You would also need to completely change the internal layout of the existing upper floor to access the rooms of the completed extension. This option would incur costs for scaffolding, roof removal and rebuilding, masonry, windows; again, plus the costs of interior finishing and rearranging the access to the extension rooms.

I would therefore recommend that you find a trusted building engineer (structural engineer) and discuss the necessary work with them. Ideally, someone specialized in renovation and refurbishment; such a professional usually has the relevant trades involved and tends to bring more creative ideas regarding existing structures compared to a building engineer who works exclusively on new builds.

Regards, Bauexperte

Hello construction expert – thank you very much.
The partition wall on the upper floor is currently at 1.80 m (5 ft 11 in) – we would completely remove it and of course redesign the entire upper floor, including windows, etc. New insulation will be needed anyway – also in the attic.
I’m sharing our floor plan ideas for better understanding.
The side extension would be in the area where there is no basement.
An extension only on the ground floor would be sufficient for us – this way we can accommodate the one missing room well and it wouldn’t be necessary over both floors.

Explanation:

The top row belongs together. Each shows the upper floor with a bathroom variant either internal or on the far right. Here the roof structure would need to be extended (basically built upon the existing ground floor structure).
The two plans on the right are for the ground floor and differ only slightly (kitchen variant).

The bottom row: the two on the left belong together.
Extension only on the side of the ground floor – so upstairs only 2 children’s rooms and a bathroom are needed.

The two on the right:
Smaller extension on the ground floor with upper floor continued.
This creates space upstairs for 3 children’s rooms plus a bathroom.

Best regards