ᐅ Semi-detached house in Hamburg with a general contractor on own land, two plus full attic floors, no basement

I’m looking for feedback on anything we might have overlooked. Tips on processes and organization are also helpful. (Details about the location, plot, and contractors involved will be shared later to keep things anonymous for now.)

We want to build a duplex and hire a general contractor (GC) for this. Each party has about €40,000 (approximately $44,000) available. The scope of self-performed work will differ slightly between the two parties but will mainly be limited to painting (including plastering and all related work) and flooring (excluding bathrooms). The attic may possibly be finished as self-performed work.

We have a few requirements:

• Each party: 2 adults (bedroom, office) + 3 children (individual bedrooms)
• Total house footprint around 165m² (approximately 1,775 sq ft). A preliminary building inquiry has already been made.
• Noise protection necessary due to aircraft noise.

We also have some preferences (order does not matter):

• Full attic living space
• kfw300 program
• Solid construction
• Brick facade
• Pitched roof
• Central ventilation system
• For both parties: rooms should not be too large (e.g., child’s room 10m² (110 sq ft), office 8m² (86 sq ft)); only one large open area for living and kitchen.
• Each half of the building should be easily separable in the future into an accessible unit (basement) and an apartment (upper floor + attic).

Full attic living space:
According to the plans, we may build two full stories. We want to retain as much garden space as possible and, for this reason among others, would like to add a fully functional attic. By “fully functional,” we mean it can be used as living and working space and forms its own separate part of the apartment—not an open area connected to the stairwell (for example, the parents’ bedroom would be here). We were advised that having a concrete floor between the upper floor and attic would be sensible to achieve this. The attic could also be raised with a knee wall (dormer wall), which would greatly improve the interior height. Since the plans don’t specify maximum ridge, eaves, or gable heights, it will likely be restricted only by required setback distances. The setback to the neighboring plot is currently set at 3 meters (about 10 feet) for driveway, bike storage, and garage as border construction. This leaves a good garden area on the other side of the house.

kfw300 program:
This is very helpful for financing, almost essential for us. However, it comes with certain requirements that may cause additional costs. Which parameters would you recommend adjusting here?

Current status:
We have discussed financing preliminarily and set a budget framework. We already own the land. We are currently in talks with several GCs (ranging from smaller architecture firms, medium-sized companies, to larger firms like Baudirekt). We plan to decide on a GC in about a month. The options each GC offers will understandably influence our decision. We also still need to clarify whether we truly need and can afford a fully finished attic or if a pitched roof attic that could be finished later would suffice. A basement would probably be more expensive and provide less livable space than a full attic, so it is no longer a serious option. We plan to consult two or three more GCs to get feedback on possibilities and pricing.

Please feel free to ask any questions! This is already a lot of help. Maybe there’s even some additional advice out there. Thanks!

There is an excellent 16-page PDF about setback requirements from the Free and Hanseatic City of Hamburg. I almost posted the link. This will likely be crucial for the current planning, especially regarding the height of the attic.

Costs: 400 plus KfW? Or inclusive? In the latter case, forget it. I roughly calculated 80% flat rate, which gets you a little over 160 sqm (1,722 sq ft) per half.

Aside from personal preferences, the requirements are so highly individual that this is something for a professional planner. Adding KfW into the mix makes it a completely different matter.

In my opinion, the budget is not sufficient. 160 + 3000 = 480k without additional costs. Without any personal labor, expect around 3,200 to 3,500 per square meter of living space.

If you don’t want to share a plan of the plot, then that’s your choice. In that case, you will hardly receive any useful answers.

Thank you (I am familiar with the city document). I will probably also provide the site plan. But the main issue right now is different: we want feedback on what we should consider to make the project coherent. We don’t want to simply maximize the built-up area...

Rübe1 schrieb:

I just roughly calculated 80%, then you get about 160 sqm per half..

80% of what? I’m afraid I don’t follow. Each half would have around 65 sqm (700 sq ft) of living space per floor. Or is that not correct?

This seems to be the key point. Space-wise, we need around 140–150 sqm (1,500–1,615 sq ft) in total for the rooms, right? But we prefer building upwards rather than using the full plot area. Does that make sense? Or are we missing something?

Rübe1 schrieb:

Aside from wishes, the specifications are so individual that this is a job for a professional planner.

Can you specify what exactly is so individual? We are open to adjusting our ideas (e.g., two full stories plus an attic, which would be more typical). What kind of savings could we expect? We just can’t really estimate how much adjusting the house design or our requirements would affect the budget.

Rübe1 schrieb:

Costs: 400 plus KfW? or including? If including, forget it.

hanghaus2023 schrieb:

In my opinion, the budget is not sufficient.

Let’s say the budget must cover the KfW funding requirements. Then the concept will have to change. Or drop KfW support, although that might reduce the budget a bit (KfW and IFB have conditions; we rely on them).

Rübe1 schrieb:

Then adding KfW, it’s a completely different story.

I don’t understand. Is the meaning that costs increase significantly?

We already have a certain focus, but the question is where we should look at the situation from a completely different perspective.

It makes a lot of sense to consider a semi-detached house as a whole. You only need to look for a general contractor (GC) for the shell construction stage; the interior work can be assigned differently by each neighbor. In theory, with joint planning, one half can have a basement while the other does not. You can find my 11ant basement rule, as well as my approach to the two-stage builder selection process (before and after the "Module B"), linked in my signature. I would recommend requesting bids from at least one more general contractor (two masonry contractors and two carpenters), as I usually consult five or six in total. In Hamburg, you should also be able to find house concepts from developer offerings for inspiration (those available nationwide are usually two full stories plus a finished attic, with about 140/145 square meters (1507/1565 square feet)). By the way, a knee wall does not increase standing height; for that, you need a full wall (which, however, often causes issues with the full-story height limit).

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1689owen schrieb:

Thanks (I’m familiar with the city document).

OK, did you also understand it? On page 7, your exact case is included. You are "planning" with a 3m (10 feet) setback from the boundary. In one case, 2.80m (9 feet) is acceptable, in another case, 3.60m (12 feet) is not, assuming the ridge height "H2" really is just 3m (10 feet). That significantly limits your plan.

1689owen schrieb:

Budget must cover kfw as well

kfw 300, are you familiar with the conditions? It’s like program 297—meaning kfw 40 plus. And beyond that, there is also the CO2 balance and all that. To quote a colleague, that won’t be so easy with solid construction. Especially not with concrete ceilings and facing bricks...

1689owen schrieb:

Each semi-detached house half can be separated in the future without much effort into an accessible unit (basement) and an apartment (first floor + attic).

That alone already requires a planning concept you can’t just pull out of thin air, so this is:

1689owen schrieb:

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

completely unrealistic besides the costs. Unless you want to crash and burn with full force...