Change of external dimensions after building permit?

Hello everyone,

I have a question about our construction project (new single-family house in NRW) and would appreciate your opinions, as I haven’t really made any progress with my own research. Unfortunately, our architect and construction company have different opinions about what is necessary and what is not.

About the problem:
According to the planning documents for the building permit, our exterior walls have a thickness of 36.5 cm. After the building permit was issued, a verification was created regarding energy savings and the use of renewable energies for heating and cooling generation in buildings. According to this verification, the exterior walls must have a thickness of 40 cm.

Our architect thinks that we can simply adjust the exterior dimensions of the house (previously: 8.49 m x 8.99 m, adjusted: 8.56 m x 9.06 m) accordingly and only need to shift the house by 4 cm on one side of the plot, since a boundary distance of 3 m was previously planned here. The boundary distances to all other sides would also be maintained with the changed exterior dimensions. No further measures except for adjustment by a surveyor would be necessary.

Our construction company says that we cannot simply deviate from the building permit to this extent. They propose an amendment of the plans, keeping the exterior dimensions of the house and changing the interior dimensions accordingly. But regardless of whether the exterior dimensions are adjusted or not, the construction company wants new plans from our architect. Otherwise, additional costs will arise due to the changed exterior dimensions, and they want to make an additional contractual agreement in this regard.

My question is, is the adjustment of the exterior dimensions and the corresponding shift still within any tolerance limits or do we need a supplementary approval / alteration to the building application? What other measures are necessary when adjusting the exterior walls either while maintaining the exterior dimensions or adjusting them? Does a new static calculation have to be done?

Unfortunately, our architect is on vacation for an extended period now and the construction company wants to begin with the foundation slab the week after next.

Personally, I would like to keep the exterior dimensions and ask our architect to adjust the plans accordingly. In my opinion, that would be the most practical solution. Since there is already a building permit in place, our floor plan would allow a corresponding reduction, no additional costs would arise with the construction company, and I hope that only plan changes from our architect are sufficient and that we do not need a new static calculation.

Thank you very much and best regards from Rhein-Sieg-Kreis!

The permit applies to a building structure with certain external dimensions at a specific location. Simply moving it is not allowed; for that, you need a Tektur. However, I would not agree to reduce the internal dimensions.

Maybe you could insert pictures of this mysterious calculation here? - my most furrowed question marks already start at the point of who is supposed to produce 40 cm thick masonry blocks specifically for your house (made of what, actually?), such a special size is not worthwhile in such a small quantity at all?

P.S.: whether to adjust the dimensions better on the inside or outside would have to be decided on a case-by-case basis. It’s best if you show the plans.

Sorry, the wall structure is of course important. We are building with sand-lime bricks with a thickness of 24 cm. According to the evidence, an insulation of 14 cm thickness is necessary plus exterior and interior plaster results in a wall thickness of 40 cm.

The attached picture shows the approved version.

Here is the calculation for the exterior walls.

[ATTACH alt="aenderung-aussenmasse-nach-baugenehmigung-642119-1.jpg"]82035[/ATTACH]