Semi-detached house in Hamburg with general contractor on own land (two + full attic floor, no basement)

I am looking for feedback on what we might have overlooked. Tips on processes and organization are also helpful. (Details about location, plot, requested companies will come later to keep this anonymous for now.)

We want to build a semi-detached house and hire a general contractor for it. Each party has about 40,000 euros available. Own contributions should be somewhat different for the two parties but are essentially limited to painting work (including plastering and everything involved) and floor coverings (excluding bathrooms). Possibly, the attic would first be completed as own work.

We have a few requirements:

[*]Each party: 2 adults (bedroom, study) + 3 children (own rooms)
[*]Total house floor area about 165m². There has already been a building pre-application.
[*]Noise protection necessary. Aircraft noise.

We also have a few ideas (order not significant):

[*]Full attic
[*]kfw300 program
[*]Solid construction
[*]Facing brick
[*]Pitched roof
[*]Central ventilation system
[*]Both parties: rooms not too big (e.g. child 10m², study 8m²), only one large open area for living and kitchen.
[*]Each half of the house can be separated in the future with minimal effort into a barrier-free part (basement) and an apartment (upper floor + attic).

Full attic:
According to the plans, we are allowed to build two full floors. We would like to preserve as much garden space as possible and for that reason among others, we would like to add a full attic on top. For us, full attic means that it can be used as living and working space and that it is an independent part of the apartment, i.e., not an open area leading to the stairs (for example, the parents’ bedroom would be located there). We were advised that a concrete ceiling between the upper floor and attic would be advisable for the full functionality. The attic could also be raised with a knee wall, which would be great for interior height. Since the plans do not specify exact maximum ridge, eaves, or gable heights, the height will likely only depend on the setback area. The distance to the neighboring plot is currently set at 3 meters (for driveway, bicycle storage, garage as boundary construction). This leaves a good garden area on the other side of the house.

kfw300 program:
This would be very helpful for our financing, almost necessary. However, there are requirements attached that could potentially cause additional costs. Which levers should we adjust here?

Current status:
We have preliminarily discussed the financing and set a framework. We own the plot. Now we are mainly in talks with a few general contractors (from smaller architectural offices over medium-sized companies to larger companies like Baudirekt). We want to decide on a general contractor next month approximately. Of course, the options offered by each general contractor also play a role. And we still need to clarify for ourselves whether we really need or want to pay for a full attic (or just an attic as a pitched roof that could be converted later). A basement would probably be more expensive and less usable as living space than a full attic, so a basement is no longer really an option. We also want to request offers from two or three more general contractors to get feedback on possibilities and prices.

Please feel free to ask! That is already a lot of help. Maybe there are one or two tips as well. Thanks!

There is a wonderful PDF from the Free and Hanseatic City of Hamburg about the setback areas, 16 pages long. I almost posted the link. That will probably be crucial for the current planning, how high the attic will be.

Costs: 400 plus kfw? or inclusive? In the latter case, forget it. I only calculated roughly 80%, then you come to just over 160 sqm/half..

Apart from the wishes, the specifications are so incredibly individual, this is something for a planner. Then kfw on top of that, that's a completely different ballgame.

In my opinion, the budget is not sufficient. 160+3000=480k without additional costs. Without own contribution rather 3.2-3.5k /m2WF.

If you don’t want to show a plan of the plot, then so be it. Then hardly any useful answers either.

Thank you (I know the document from the city). I will probably also provide the plan for the property. But the concern is something else for now: feedback on what we should think about so that the project becomes coherent. We don’t want to maximize the built-up area...

I just roughly calculated 80%, then you come to about 160 sqm/half..

80% of what? I can’t really follow. Each half would have about 65 sqm of living space per floor. Right?

This seems to be the starting point. In terms of rooms, we actually need around 140-150 sqm (right?). But we prefer to build upwards rather than use the entire area. Does that make sense? Or where are we thinking wrong?

Apart from the wishes, the specifications are so individual that this is something for a planner

Can you say what exactly is so individual? We can still adjust our ideas (e.g., two normal full floors plus attic, which would be more normal, right?). And what kind of savings could be expected? We just can’t really estimate which adjustments to the house or the ideas would be necessary for the budget.

Costs: 400 plus kfw? or including? In the latter case, forget it.

In my opinion, the budget is not sufficient.

Let’s say: the budget must be sufficient including kfw. Then something about the idea has to change. Or exclude kfw, although then the budget would probably be a bit lower (kfw, ifb have requirements; but we depend on them).

Then add kfw, that’s a completely different matter.

I don’t understand that. Does it mean the costs would increase significantly?

We are just somewhat focused, and the question is where we should look at the situation from a completely different perspective again.

It is very reasonable that you understand a duplex as a whole. You only need to look for a joint general contractor at the shell construction level; you can assign the interior finishing differently from the neighbors. Theoretically, with joint planning, one half can have a basement and the other not. You can also find my 11-point basement rule as well as my approach to the two-stage contractor selection (before and after the "Module B") via my signature. You cannot yet use private messages here in either direction. I would recommend you request another general contractor (two bricklayers and two carpenters); I usually take five or six in total. In Hamburg, you should definitely find inspiration from house concepts offered by developers (those offered nationwide are mostly II+D with around 140/145 sqm). By the way, a knee wall does not help with standing height, that would be a wall plate (which, however, often would also break the full-storey line).

Thanks (I know the document from the city).

OK, did you understand it too? On page 7, your case is exactly included. You are "planning" with a 3m boundary distance. In one case it fits with 2.80, in the other it doesn't with 3.60, assuming that it is really only 3m up to the ridge tip "H2". That considerably restricts your plan.

The budget must be sufficient including kfw

kfw 300, do you know the conditions? It is like program 297. So kfw 40 +. And beyond that yes, CO2 balance and all that. To use a colleague’s words, that won’t be so easy with solid construction. Especially not with concrete ceilings and clinker...

Each semi-detached house can in the future be divided without much effort into a barrier-free part (basement) and an apartment (upper floor + attic).

That alone already requires a planning concept that you can’t just pull out of your pocket, according to which:

We want to decide on a general contractor roughly next month.

is completely unrealistic besides the costs. Unless you want to crash and burn at all costs...