Cost estimate single-family house with granny flat in Hessen

Our budget for the project is about 500k. We need the KfW standard in order to access the KfW funds.

I can gladly provide information about the areas if relevant. How do you see the conditions and our budget regarding the whole thing? We are very grateful for tips and advice. :)

So what exactly is the budget now? 500,000€ all-in for the house construction and everything around it? Or do you still want to cover the plot & ancillary building costs from that? You can only guess like this. Much has already been said about the granny flat. For 1000€ per m2 you might be able to extend the house by one meter of masonry, but certainly not get a complete additional apartment with windows, etc.

A basement definitely lies in the six-figure range with excavation work & soil disposal, and the white tank & KfW do not make it cheaper. I see that as absolutely unfeasible.

Clarify your current plan budget exactly – including the plot, land purchase, notary, and all ancillary building costs. Alone your utility connections can cost several tens of thousands of euros.

Hm to be honest, I have that feeling too. Do you possibly have tips on how to best structure something like this or with whom, in your opinion, we should exchange ideas before planning a shaky house of cards that later collapses or overwhelms us with costs.

How to best structure this, you can read here with the keywords Hausbau-Fahrplan, Gerddieter, Eigenvergabe and more as well as in my "Ein Hausbau-Fahrplan, auch für Sie: das Phasenmodell der HOAI!" (on Bauen jetzt). You should definitely exchange ideas with an independent building consultant, who does not want to sell you anything. A builder wants to sell you something – not least: consider you dumb – when he talks about an 80 sqm granny flat for an additional 90k. Since you are looking for a shell construction contractor or one for the finishing stage "ready to move in minus," he couldn't care less if at the end of his contract volume you also run out of money. You should not go to such sharp dealers without independent advice.

The preliminary draft is in the making. We have an interim status, but the final design planning will still take a little while. I could at most show you our interim status.

I am currently desperately waiting for the architect's planning so that I can create a more accurate calculation

I fear, on the one hand, you are using the term preliminary draft incorrectly, and on the other, that your architect (with quotation marks?) does not produce a proper planning with a preliminary draft, but merely drafts that are still being tinkered with until they are either at least good to your layman’s eyes or you are completely exhausted hoping for improvements in the next attempt. That is what the signal word "interim status" tells me, which does not exist for a preliminary draft; and the buzzword "final."

We can probably disregard the . I’m already happy if we have a marching plan for the house itself.

That already speaks for a beginning fatigue caused by the planning grind.

0-10 degrees is unfortunately given by the development plan. It was not a decision of ours :-(

But that is a nasty development plan which we should know better. You are not allowed to link it here, but you may name it: "Model town no. 123 in the cool valley" or so.

How do I best explain why we have so fixated on solid construction? We just like it. In the model house park we simply liked the feeling in stone houses better. KfW 40 actually within the framework of the to benefit from the low-interest loans.

Rental income from a granny flat is eye-wash, especially with making the additional subsidy for KfW40 attractive. There are plenty of threads here about such untrustworthy matters. Were you in Mülheim-Kärlich? (As far as I know, there are no stone houses in Bad Vilbel?) – I generally recommend you make the construction method decision during the dough resting period. Apart from solid or wooden construction, the feeling in house exhibitions is also influenced by the topic of controlled residential ventilation, which homebuyers mostly do not have at home yet.

Which tenant would want to move into a granny flat where the outdoor areas will still be a construction site or wasteland for the next 2 or 3 years?

The fitted kitchen is not expensive, the expensive parts are the front door, separate stairwell, bathrooms, tiles, etc.

I am currently building a single-family house with a [Einliegerwohnung], it costs about 250k for 77 sqm, 100k is absolutely unrealistic, in my case the [Einliegerwohnung] is only on the ground floor, a staircase that you would need hardly makes sense due to space and cost reasons. Currently, you are looking at about 3k per sqm, plus or minus 15% depending on the equipment and requirements – your price expectations are unrealistic.

Oh yes, for the basement, depending on the floor, my estimate is 120-180k, based on the experience I have had.

Simple rule: 240 sqm * 3000€/sqm costs = 700k just for the house. Clearly over budget. If you leave out the granny flat (not clear what it's good for), then it might work better (but still tight).

I have already read the figure 2,500 - 3,000 €/m2 several times for the calculation of flat-rate construction costs here in the forum. But nowhere does it say what they include. Are these the pure construction costs? Are incidental construction costs already included? Outdoor facilities? Plot of land? Could someone explain to me how this flat-rate figure should be understood?