ᐅ Living area approximately 8 m² smaller in the permit drawings compared to the design (general contractor)

Hi everyone,

Unfortunately, I thought I was smarter than everyone else here in the forum (I have been a quiet reader for a while) and believed I could rely on the general contractor’s planning. Now, right from the start, things are becoming "interesting." I’m not sure whether my frustration is justified or if this is just standard practice in the construction industry. Here’s the situation:

Based on the preliminary design from the general contractor, we awarded the contract (signed the agreement) with the expectation that the room sizes would match the preliminary design. The house is planned as a KfW 40 energy-efficient building with sand-lime brick, insulation, and brick veneer. This was included in the offer along with additional requests, and the design was adjusted accordingly, if necessary. So, it’s not like the general contractor was unaware of our KfW 40 project. Now we have received the building permit drawings showing roughly 8 m² (86 sq ft) less living space due to suddenly thicker walls, both external and internal. The exterior walls were increased from 42.5 cm (17 inches) to 49 cm (19 inches) thickness. And this was done inward, not outward. In other words, each side has lost 6.5 cm (2.5 inches) of interior living space. Calculated in euros, that’s about €22,000 less living area based on the price per square meter. Or, in other words: the general contractor now has to buy fewer sand-lime bricks and build with less material, with less plastering, tiling, screed, underfloor heating, pipes, etc. However, there was no price reduction.

Is this common practice? Should one accept something like this?

Additionally, the attic floor has lost 13 cm (5 inches) in width and 6.5 cm (2.5 inches) of interior height due to the knee wall being shifted further inward. We had planned to convert this space later, which now seems hardly worthwhile. The general contractor knew about this in advance and even planned wiring and such in the attic/roof space.

How do you assess this situation, and how would you proceed?

Thank you very much in advance!

ITSM2025 schrieb:

The exterior walls were widened from 42.5 cm to 49 cm (17 inches to 19 inches). And this was done inward, not outward. In other words, each side now reduces the living space by 6.5 cm (2.5 inches) inside. Calculated in euros, this equals about €22,000 less living area, based on price per square meter. Alternatively: the general contractor now has to buy fewer sand-lime bricks and build with less material, later requiring less plaster, tiles, screed, underfloor heating, pipes, etc. However, this did not lead to a price reduction.

The wall is still the same length on the outside. So fewer bricks and less plaster shouldn’t be needed. If the general contractor simply extended the wall outward, the roof would also have to be larger, and setbacks on the plot, for example for the garage, might no longer fit. For this reason, it’s probably not unusual that the space is taken from the inside instead. But maybe there are other opinions.

Why does the roof absolutely have to be larger? With a hip roof, you can simply reduce the overhang. And if an additional 14cm (5.5 inches) in the overall dimensions is a problem, then the plot is probably too small for the planned house.

Apart from that, a roof can also be redesigned. An experienced master carpenter can do this within about an hour using the appropriate software.

I have never heard of increasing the exterior walls inward.

One more thing.
The question is, what exactly is living area? There are different definitions according to the Living Space Ordinance (Wohnflächenverordnung) and DIN 277.
If I remember correctly from our building permit / planning permission (from 2013), you can see there how the living area is calculated according to the Living Space Ordinance, with deductions for plaster and so on.
In my opinion, DIN 277 tends to be somewhat more generous when it comes to the area.

If you calculate 6.5cm (2.6 inches) for a two-story 10 x 10 m (33 x 33 ft) standard house, you should not be nearly 5 m² (54 sq ft) less in area. You can see that there are likely deviations from the 8 m² (86 sq ft).

ITSM2025 schrieb:

Preliminary design from the general contractor (GC)

Define preliminary design.

ITSM2025 schrieb:

This was included in the offer along with additional requests and, if necessary, the design was adjusted accordingly.

So, you probably have small print. And it depends on the contract. Ultimately, you are building with a general contractor. The question is how the GC determines the price in the first place. Often, the GC bases their pricing on a catalog house or on drawings that are part of the contract, including the scope of work description.

ITSM2025 schrieb:

Calculated in euros, that’s about €22,000 less living space if we look at the price per square meter.

When building with a GC, it is very rare to have pricing strictly based on living area. Often, the standard Florentine model house has about 150 m² (1,615 sq ft) of living space on a concrete slab and the corresponding scope of work description. Any adjustments are made based on special requests, including energy-related adaptations. The scope of work references the Renewable Energy Act (or formerly KfW standards), which the catalog price relates to.
Then adjustments are made, sometimes resulting in a slight loss of a few centimeters in dimensions, or changes in height. For example, the roof pitch often needs to be modified to comply with the local development plan or if the client wants a different staircase.
And this should also be stated in the contract.
However, I am not aware of any GC committing to fixed figures upfront. They keep some flexibility so that adjustments do not require a complete recalculation.
If you are unhappy with this regarding your building permit / planning permission, you should discuss it. You don’t have to sign it, but you should clarify to what extent living area is capped in the contract.

ITSM2025 schrieb:

Or put differently: the GC now has to buy fewer calcium silicate bricks and build with less material, later also less plaster and tiles, screed, underfloor heating, pipes, etc. But no price reduction took place.

Such a thing rarely happens with a general contractor. This is not an architect’s house with a tender process, but a turnkey house according to the scope of work description for you as the client. Let’s just say: the cost averaging is not something you as the client need to worry about. It is simply based on standard model houses, their specifications, and additional options.

ITSM2025 schrieb:

Also, the attic space lost 13 cm (5 inches) in width and 6.5 cm (2.5 inches) in interior height due to the knee wall being moved inward. We originally intended to convert it later, which now hardly makes sense anymore.

Is the difference of a few centimeters really making a conversion not worthwhile? That seems unreasonable.

The lot is more than large enough. According to the floor area ratio, we could almost double the size. So, there are no issues in that regard. To calculate the reduced “living area,” I compared the area from the initial design with that from the drawings we have now received for the building permit / planning permission application. Due to the 6.5 cm (2.6 inches) inward shift of the 17.5 cm (7 inches) calcium silicate masonry, the area is missing. For example, the living room alone has shrunk by 2.5 square meters (27 square feet). In my opinion, this simply cannot be right. On what basis was I supposed to sign the contract if not according to the original design? Furthermore, we are also paying an additional fee for upgrading to KfW 40 standard. I am just interested in how the legal situation stands now. Doesn’t the general contractor owe me at least approximately the area in the individual rooms as originally planned? We didn’t want anything other than KfW 40 because of the requirements. That was clear. You can’t just plan ahead with narrower masonry like that.