Build a prefabricated house over an old existing basement?

Pine Avenue Variant 1 from Gussek Haus

Kiefernallee Variante 1 von Gussek Haus

There is definitely something that can be worked around. Although it has a gable roof and is therefore sensitive to offsets on the eaves sides; thanks to the knee wall, however, it is still possible to trick it.

Quickly scribbled down how something like this could look:



1. Floor plan of the house only slightly changed in depth
2. Offset incorporated
(Externally it can remain as it is with the bay window; in the example I sacrificed the shower in the guest WC to move the door)
3. House width unchanged, the overhang can be added next to the old basement (only foundations are needed, no rooms underneath, this side has no windows in the existing basement)

In the example, the slight adjustment of the house depth is not shown. Purple marks the outlines of the basement, orange the "extension" of additional foundations. Otherwise, only the ceiling of the basement would be at least partially new.

I currently lack the time to show more details (like the upper floor demonstration) – but even on the upper floor, rather small changes would suffice.

: Thank you for the idea. It doesn't look bad at all, even though you would probably lose a few square meters because of it. It might get a bit tight for the third children's room (yes, we do need all three children's rooms ).

You probably hardly get around using as much as possible of the exterior walls of the existing basement.

Certainly all somewhat cheaper than a completely new basement.

Should the inspection be done with an architect or a structural engineer, or can an architect do both?

Just quickly recalculated. That would mean losing about 20 sqm of living space. That’s quite a bit.

And upon closer inspection, I can't really imagine the offset roof either.

So maybe there’s still the option to build new foundations on three sides and thus also close all the basement windows, right?

Would something like that be feasible or do you generally advise against it?

Any idea what something like that might cost?

I don’t see any area being lost, certainly not 20 sqm. If you took my simplified sketch 1:1 at face value – which it is not meant for, but only to basically show how it is feasible – then you would lose about 4 sqm in the area of the door between the hallway and the living room.

But first of all, it is only a principle sketch – just for illustrative purposes without detailed tricks – and secondly, you can recoup that when extending to the left (but for that you would have to set the plot with building window / setback areas so you can tinker with it).

The technical room can be moved to the basement, which allows the ground floor layout to be changed again.

Also on the upper floor – I only currently lack the time to demonstrate this, as it is somewhat more complex to put together – I don’t see any significant losses threatening: some savings can be made at the air space above the entrance and the “gallery”; otherwise, it’s more shifting around than shrinking. Overall, there it is also only a minor operation under local anesthesia.

I have not touched the light wells, and consider them likely to be preserved without major changes.

The architect does not yet need the structural engineer for the general feasibility (which I consider given), but for the later approval planning.

As a precaution, assume that the existing basement ceiling will be completely removed and rebuilt. This also makes it easier to remove the oil tanks.

Otherwise, I consider the basement to be preservable as is, including lighting and location of the external staircase. The house design will be re-planned without loss of area. Exactly what is possible depends on the degree of leeway to the left side of the plan.