Cost estimate for prefabricated house with own effort

And possibly quite a bit is still missing.

Incidental building costs can range from 30 thousand up to sometimes 50 thousand. The BoPla is not included. It is listed separately or with the house. That can be between 20-30 thousand.

A soil report for the new development area can be a guideline, but one should definitely commission a separate one for the house warranty.

It would be important whether 2 residential units can be built on it.
I would calculate the other way around: what is financially possible for you? Subtract the plot from that, then incidental building costs of about 3000€ from the calculation. What remains? What is then “in the house”?

Thanks, I’ll take that into account. Without a concrete offer, of course it will be difficult. I had hoped that at least a rough guideline could be established.

2 residential units are possible, similar projects have already been realized on the street.

Total costs of about 550k € would be acceptable – excluding kitchen and any new furniture. That leaves 300k € for the semi-detached house. Sounds a bit low at first, which is why we want to do a lot ourselves.

So, that leaves 300k € for the semi-detached house. Sounds like little at first, which is why we want to do a lot ourselves.

My brother-in-law is a civil and landscape builder with his own company (excavator, trucks, etc.), I think we are not entirely unskilled in craftsmanship. We also have access to painters and heating engineers in the family, a friend who is an architect, and if necessary, access to trained or inexpensive helpers.

Check if you, especially you as a young father, can manage this in terms of time (and physically). In my environment, both spouses have always worked on the DIY tasks. This is only possible to a limited extent with small children. The brother-in-law (hopefully the one who wants to help build?) being a civil and landscape builder is a great help with the earthworks. However, of course, he has to earn money during his main working hours just like you. And helpers also need to be paid. Honestly, I read little about DIY work. If you don't do it yourself, meaning without labor costs, but have to pay wages, you get close to a turnkey house build, since with that you usually have to lay the floors yourself, paint the walls, or the underside of the roof. There is a difference between doing it yourself (labor costs = 0) or hiring someone whom you have to pay, even if relatively less.

There are several threads here about semi-detached houses as a way forward. Plan and construct the semi-detached house together, although the halves may differ if desired. The primary importance is the alignment of the house profile on the shared side. Ideally, construction is carried out with the same contractor up to the weatherproof shell, after which both neighbors are free to go their separate ways. So take one common planner and one common shell construction general contractor. It does not have to be a timber frame panel builder. Neither the total costs nor their distribution between shell construction and finishing would be noticeably cheaper with one construction method or the other, and even in "solid" houses there are plenty of opportunities to create non-load-bearing interior walls either in lightweight construction or masonry by oneself.

I would definitely contract out the foundation slab as a precaution. Possibly we could do the earthworks ourselves, but that would probably not result in any significant cost savings. The plot is fairly flat, excavation would be minimal. A basement would be nice but probably not feasible cost-wise. Since it is already developed, I assume that no further significant additional costs (surveys etc.) will arise.

A foundation slab is popular among many building contract contractors to exclude from the scope of work. But that is unfairly divided: their advantage and your problem. Do not agree to that under any price argument; the foundation slab must be included in the scope of work of the general contractor / house manufacturer. For the first and second 11ant basement rules, the external search will guide you to (include quotation marks!) "With or without basement: a rule as a decision-making tool" (it also states "A semi-detached house has two halves"). Development does not mean lower ancillary costs and certainly no dispensability of soil surveys.

Check whether you, especially you as a young father, can manage it time-wise (and physically). In my environment, both spouses have always worked hard on DIY tasks. That only works to a limited extent with small children. That the brother-in-law (hopefully that’s the one who wants to help build?) is a civil and landscaping engineer really helps with the earthworks. However, of course he has to earn money during his main working hours just like you. And helpers also have to be paid. To be honest, I read little about DIY work. If you don’t do it yourself, meaning without labor costs, but have to pay wages, then you come close to turnkey house construction, because with that you yourself usually have to lay the floors, paint the walls, or do the underside of the roof. There is a difference whether I do it myself (labor cost = 0) or hire someone whom I have to pay, even if in a smaller proportion.

My own home would be worth it to me. With the prices, we will hardly be able to afford anything of our own otherwise. Inflation alone is running away with my savings.

Brother-in-law is helping build, correct. That’s why I trust myself to do it; I wouldn’t do it alone. And the goal, as I said, is to do as much as possible myself.