ᐅ Is it practical to build a prefabricated house using a solid construction floor plan?

Hello everyone,

We have just purchased a plot of land in NRW. The previous owners had already hired an architect to fully oversee the construction using traditional masonry methods and have already paid over €50,000 (about $54,000) for phases 1-6. There is already a building permit / planning permission, so construction could start almost immediately.
However, we are planning to build using prefabricated construction and are now wondering how to proceed best. The previous owners have offered to sell us their plans. Either way, we would still need to modify them (aside from the exterior dimensions) to fit our requirements.
The plot is on a slope, and there aren’t many options for building on it, so the design would likely be very similar either way.
Does it make sense to buy the plans from the previous owners and then work with the architect to incorporate changes before approaching prefab house manufacturers? Or are the floor plans not very useful due to the different construction method, making it more reasonable to hire a different architect for a new design?
And if you were to buy the plans—how much would you pay (they don’t really have a strong bargaining position)?

We are completely at the beginning of our home-building journey, so I apologize if this is a naïve question... We just don’t really know the best way to start.

I don’t think there is a significant difference in the house itself whether it is built by a prefab house supplier or a traditional solid construction builder.

However, I’m quite sure that you don’t really want to take over the previous owner’s proposal as it is. Since the previous owner can’t use the documents anymore anyway, you can offer them €100 - €500 as a goodwill gesture and use the documents as a sample or source of inspiration.

Haus Luni schrieb:

I believe that regarding the house itself, it doesn’t make much difference whether a prefab house supplier or a traditional masonry builder is used.

However, I’m quite sure you don’t really want to fully adopt the previous owner’s proposal anyway. Since the previous owner can’t use the documents anymore, you could offer them €100 - 500 as a goodwill gesture and use the documents as samples or inspiration.

In theory, it doesn’t make a difference, but we are leaning more towards a timber frame construction. We were thinking more about €5,000, but even that seems, in my opinion, a bit “bold” considering what they paid... We originally wanted to have an architect’s plan first and then approach the home builders with it. The question is also whether you save anything by using their plans or if it makes no difference and it’s better to commission your own architect.

I would make the amount dependent on the added value for you. You mentioned that adjustments to the planning are necessary, meaning the previous plans are of little use to you and you will have to redo almost everything anyway. That is why 5,000 euros is too generous.
For the ground survey and service phase 1, I consider 1,000 euros to be more than fairly paid.

I recommend that you educate yourselves thoroughly about the planning process. Only those who know a lot can avoid being taken advantage of. Here are a few points to consider:

- To build a house, you basically need an approved building permit plan and a structural engineering calculation.
- The building permit plan must be submitted to the local authority, but the structural calculation does not.
- The building permit plan can be signed by any master builder, building technician, architect, or many professionals trained in construction. It does not necessarily have to be done by an architect!
- A building permit plan is binding in many areas, but some things remain flexible. For example, you can still move windows or change interior layouts.

So, there are many ways to reach your goal.

For example, we planned the entire floor plan and the outdoor area ourselves, drawing everything on paper while trying to comply with the legal requirements. Since we are not professionals, we found someone to create the building permit plan for us. A few points had to be corrected. After the building permit plan was approved, a structural engineer calculated the static load. Of course, we had already taken structural considerations into account during planning to avoid proposing something impossible. This approach was significantly cheaper.

Therefore, it is not presumptuous; you just need to recognize the value behind it. If you buy a car for $50,000 and it breaks down after the warranty expires, you simply don't get any money back.

Is it really true that in North Rhine-Westphalia, structural calculations do not have to be submitted with the building permit application at the very least? I would find that quite surprising.

In any case, this will definitely look different for a timber frame house compared to a solid construction. It is very likely that some adjustments will need to be made purely for structural reasons. And if the floor plan has to be changed, the structural calculations will also need to be revised.

I doubt that this can still be accepted as part of a draft plan.

Some aspects of the detailed planning (probably the base area, window and door connections, etc.) will also have to be reconsidered in timber frame construction. Bill of quantities (BOQ) will probably not be needed or usable with a prefabricated house company.

Therefore, I don’t see how more than the conceptual design can be practically adopted – and I wouldn’t offer more than that, as you will most likely have to pay again for everything else with the new or previous architect and prefabricated house company anyway.