ᐅ Cost Estimate for a Prefabricated House with Owner-Performed Work
Created on: 14 Apr 2025 09:56
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PurpleBee
Hello everyone,
In our area (greater Stuttgart), there is a 500 sqm (5,382 sq ft) plot of land for sale in a very good location. The price is 450,000 €. The plot is serviced and ready for immediate construction. Building on the plot alone is financially absolutely not feasible for us (both 32 years old, one child + one planned), so we would like to build a semi-detached house. My sister and brother-in-law with two children are also interested in building, and we can well imagine doing it together.
My brother-in-law is a civil and landscape construction contractor with his own company (excavators, trucks, etc.), and we think we are quite skilled with DIY work. We also have access to painters and heating technicians within the family, a friend who is an architect, and if needed access to trained or affordable helpers.
We can well imagine taking on at least the entire interior finishing ourselves (or subcontracting if necessary). To get the ball rolling, I would like to make a first rough cost estimate. The prefabricated house should come as a shell with exterior facade, windows, front door, staircase, roof, and connections included. This and other items (e.g., electrical work) would of course need to be finalized with the supplier. I would also likely subcontract the foundation slab to be safe. We might take on the earthworks ourselves, but that probably would not save us much money. The plot is mostly level, with minimal soil removal needed. A basement would be nice but probably not financially feasible. Since the land is already serviced, I assume there will be no significant additional ancillary costs (surveys, etc.).
I have estimated the following costs and would be interested to hear your opinions. As I said, I have no concrete offers yet (except for the land cost). The goal is just to roughly check the feasibility or financing.
At first glance, this seems high to me considering that we plan to do a significant part of the work ourselves. Turnkey semi-detached houses here start at around 650,000 €. Is my estimate too high? Where do you see potential for savings? Have I missed any important items?
In our area (greater Stuttgart), there is a 500 sqm (5,382 sq ft) plot of land for sale in a very good location. The price is 450,000 €. The plot is serviced and ready for immediate construction. Building on the plot alone is financially absolutely not feasible for us (both 32 years old, one child + one planned), so we would like to build a semi-detached house. My sister and brother-in-law with two children are also interested in building, and we can well imagine doing it together.
My brother-in-law is a civil and landscape construction contractor with his own company (excavators, trucks, etc.), and we think we are quite skilled with DIY work. We also have access to painters and heating technicians within the family, a friend who is an architect, and if needed access to trained or affordable helpers.
We can well imagine taking on at least the entire interior finishing ourselves (or subcontracting if necessary). To get the ball rolling, I would like to make a first rough cost estimate. The prefabricated house should come as a shell with exterior facade, windows, front door, staircase, roof, and connections included. This and other items (e.g., electrical work) would of course need to be finalized with the supplier. I would also likely subcontract the foundation slab to be safe. We might take on the earthworks ourselves, but that probably would not save us much money. The plot is mostly level, with minimal soil removal needed. A basement would be nice but probably not financially feasible. Since the land is already serviced, I assume there will be no significant additional ancillary costs (surveys, etc.).
I have estimated the following costs and would be interested to hear your opinions. As I said, I have no concrete offers yet (except for the land cost). The goal is just to roughly check the feasibility or financing.
- Half of the plot including ancillary costs: 250,000 €
- Prefabricated house as a shell (approx. 120-130 sqm (1,292-1,399 sq ft), 75 sqm (807 sq ft) footprint, 7x11 m (23x36 ft)): 250,000 €
- Material costs (flooring, landscaping, wall work, plumbing): 50,000 €
- Heating: 30,000 €
- Ancillary costs (construction electricity, foundation slab, utility connections): 30,000 €
- Total: 610,000 € plus any potential gratuities
At first glance, this seems high to me considering that we plan to do a significant part of the work ourselves. Turnkey semi-detached houses here start at around 650,000 €. Is my estimate too high? Where do you see potential for savings? Have I missed any important items?
P
PurpleBee14 Apr 2025 13:26ypg schrieb:
And there may still be quite a bit missing.
Additional construction costs can range from 30,000 to sometimes 50,000. The building permit / planning permission is not included in that. It is listed separately or with the house itself. That can range from 20,000 to 30,000.
A soil survey for the new development area can serve as a guideline, but it is definitely necessary to commission your own for the house warranty.
It is important to know whether two dwelling units can be built on the property.
I would calculate it the other way around: what is financially possible for you? Deduct the land price from that, then deduct additional construction costs estimated at 3,000€ (about 3,300 USD). What remains? What is left for the house itself? Thanks, I will take that on board. Without a concrete offer, it’s naturally difficult. I had hoped to at least establish a rough benchmark.
Two dwelling units are possible; similar projects have already been completed on this street.
Total costs of around 550,000€ (about 610,000 USD) would be acceptable—excluding the kitchen and any new furniture. That leaves about 300,000€ (about 332,000 USD) for the semi-detached house. That sounds a bit low at first, which is why we want to do a lot of the work ourselves.
PurpleBee schrieb:
So, that leaves €300k for the semi-detached house. That initially sounds like not much, which is why we want to do a lot of the work ourselves.PurpleBee schrieb:
My brother-in-law runs his own earthworks and landscaping company (excavators, trucks, etc.), and I think we’re reasonably handy ourselves. We also have access to painters and heating engineers within the family, a friend who is an architect, and, if needed, access to skilled or affordable helpers. Make sure you consider whether you, especially as a young father, can manage this in terms of time and physical effort. In my experience, both spouses usually work hard on DIY tasks, which is only partially possible with small children.
If the brother-in-law (hopefully the one who will help build?) works in earthworks and landscaping, that’s a significant advantage for the excavation work. However, he also needs to earn money during his regular working hours, and helpers will have to be paid too.
Honestly, I see little about DIY work here. If you’re not doing the work yourself (meaning zero labor costs), but have to pay wages, the total cost will approach that of a turnkey house. With turnkey construction, you often have to do finishing tasks like laying floors, painting walls, or installing soffits yourself anyway. There’s a big difference between doing the work yourself (labor cost = 0) and hiring someone you need to pay, even if at a lower rate.
There are several threads here about semi-detached houses as an approach. Plan and construct the semi-detached house together, though the two halves can differ. The primary focus should be on aligning the house profiles on the common side. Ideally, use the same contractor up to the weather-tight shell stage; after that, both neighbors are free to pursue separate paths. So, hire a joint designer and one general contractor (GC) for the shell construction. The contractor does not have to specialize in timber frame construction. Neither the overall costs nor their division between shell and interior work would be significantly cheaper with one building method compared to another, and even in a “solid” house there are plenty of opportunities to build non-load-bearing interior walls in lightweight or masonry construction on your own.
The foundation slab is often a popular item for many building contractors to exclude from their contract package. However, this division is unfair: it benefits them and causes problems for you. Do not agree to separating the foundation slab from the contractor’s scope for any price argument—the foundation slab must be part of the GC’s or house builder’s contract package. For the first and second 11ant basement rules, use an external search with the exact phrase "Mit oder ohne Keller: eine Regel als Entscheidungswerkzeug" (it also says “A semi-detached house consists of two halves”). Having utility connections does not imply lower extra costs, and certainly does not rule out the need for a soil survey.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
PurpleBee schrieb:
I would definitely assign the foundation slab to the contractor. We might be able to do the earthworks ourselves, but that probably wouldn't lead to any significant cost savings. The plot is fairly flat, so excavation would be minimal. A basement would be nice, but is probably not feasible from a budget point of view. Since the plot is already connected to utilities, I assume there won’t be any significant additional extra costs (surveys, etc.).
The foundation slab is often a popular item for many building contractors to exclude from their contract package. However, this division is unfair: it benefits them and causes problems for you. Do not agree to separating the foundation slab from the contractor’s scope for any price argument—the foundation slab must be part of the GC’s or house builder’s contract package. For the first and second 11ant basement rules, use an external search with the exact phrase "Mit oder ohne Keller: eine Regel als Entscheidungswerkzeug" (it also says “A semi-detached house consists of two halves”). Having utility connections does not imply lower extra costs, and certainly does not rule out the need for a soil survey.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
P
PurpleBee14 Apr 2025 14:11ypg schrieb:
Make sure you can manage this in terms of time (and physically), especially you as a young father.
In my experience, both partners usually contribute to the self-build work. With small children, this can only be done to a limited extent.
If your brother-in-law (hopefully the one who wants to help build?) is a civil and landscape construction worker, that really helps with the earthworks. However, he has to earn money during his main working hours just like you do. And assistants also need to be paid.
Honestly, I don’t hear much about self-build work being done. If you don’t do it all yourself—meaning without labor costs—but have to pay wages, then you’re close to turnkey construction. Even in turnkey builds, you often have to install the floors yourself, paint the walls, or finish the underside of the roof. There is a difference between doing it yourself (labor cost = 0) and hiring someone you have to pay, even if less in comparison. My own home would be worth it to me. At these prices, we will hardly be able to afford anything of our own otherwise. Inflation alone is eating away my savings.
Yes, my brother-in-law is helping to build. That’s why I feel confident taking this on—I wouldn’t do it alone. And the goal, as I said, is to do as much of the work ourselves as possible.
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