Property development - basement yes or no?

Are you planning your budget with or without the plot? Here in the South, the prices per square meter of 2500-3000€ can be seen without additional costs, landscaping, kitchen, etc. Just the house on the slab.

I would recommend you to make a proper calculation. What does the house cost with provider X, what does it cost with provider Y. What do I still have to do extra with X so that I have the same as in the offer from Y. What do kitchen, paving, utility connections,... cost me, and then sum it all up. That way you can see how much budget is actually left.

Is it rather unlikely to encounter a good, trained architect at a prefabricated house provider?

Not necessarily the ability is the problem, but they simply won’t have the time to provide you with comprehensive advice. Some do a bit because of professional pride, I suppose, but in our experience and the reports from the provider groups on social networks, the architectural service is often a stumbling block.

At least we have already spoken to providers who did not rule that out. One even provided us with the complete specification catalog including prices in advance. Unfortunately, though, that is really the absolute exception.

Great, that is what I wished for our construction project, but unfortunately did not receive from any provider. This provider would be my favorite if they have no significant restrictions. I wonder who benefits from keeping customers in the dark like this. Providers should also be interested in comparability so they can present their special quality as an advantage. I wish that builders could, like when buying a car, compile everything online, see the price, and then order the house. No idea why this is not done or why it is not supposed to be done. Simply click, click, click, with the corresponding information at each point, which you can then google if interested. For example, you have to do that anyway with a circulation pipe.

The stated budget is only for the house and ancillary costs. But if the additional construction costs are usually not included in the price per square meter, I can better understand our architect's statement. We are currently working on the calculation, but we still need to be patient. The first offers with actual prices will probably come in about 3 weeks.

Did you finally decide on a prefab house provider? Or are you building with an architect? What was decisive for you?

The disadvantage is that the provider charges well for it and is therefore rather in the upper range. Unfortunately, he only offers catalog houses. As long as you only want to make changes inside, that's fine, but if you want to make changes to the width/length yourself because no layout really fits the plot, it quickly gets really expensive. However, they have a pretty good reputation in construction.

And if you’re going up to service phase 6 anyway, it would be pretty silly not to also commission service phases 7 + 8, right?
But if we actually go the whole way with the architect, then we have the risk of exploding prices again. Or how do you see it?
Would you counteract that by awarding a contract to a general contractor in service phase 7 and then negotiating the price guarantee with them from that point on?

Yes, I preferably recommend concept design, detailed design, tendering, and site supervision all from the same source. In the tendering phase, it’s obviously not just about materials, quantities, and volumes, but also about execution time windows and price binding deadlines. I don’t know who keeps stuffing the build client’s head with this nonsense that price guarantees only exist with the general contractor.

What surprises me is that at our initial meeting with the mentioned architect, the gist was that with 600,000 euros we could build a house of about 140 m² (without a basement). In the preliminary talks with prefab house suppliers, it was said every time that without a basement, 170 - 180 m² is also possible.

There is no reason to be surprised that apples and oranges are unequal in size: the architect means the whole money, and the turnkey supplier (regardless of construction type) only means the money you are willing to give them (i.e., as if you were secretly handed some cash by grandma for the construction-related positions). Also, these are premarital promises from used car dealers, whom you shouldn’t believe too much. They don’t care if you have to sell the house afterward to pay for it. They have often experienced that the one with the sweetest promises gets the contract. They don’t use your bathroom—so they don’t care if, to save your budget, you downgrade the tiles again.

That it’s unlikely to meet a good, trained architect at a prefab house supplier? ;)
Does that mean in reverse that the only thing I can do with prefab house suppliers is to specify the desired floor plan upfront, to at least be able to somewhat compare the house layouts?

already explained this in post #46 that you can indeed be sent to a fully qualified architect by the house manufacturer. You can get a floor plan from every house manufacturer like you would from any of their competitors (or even from a competitor’s catalog), but then every wall and door will be shifted about plus or minus ten centimeters left or right because in their system otherwise a "post" would be in the way. In the overall exterior dimensions, translating a Huber house to a Schmitz house or vice versa can differ by up to half a meter.

Our idea was to commission service phases 1-4 and then go to the prefab house suppliers with the result. Or did you mean that with "bumbling around with self-made requests for proposals"?

By bumbling around with self-made requests for proposals, I mean going on the hunt for the unfortunately only seemingly cheapest offer with requests that are explosively imprecise from a professional perspective. If you mean turnkey general contractors with prefab house suppliers including the masonry types, then I have already said several times that you cannot build a house from the permit plans, but only are allowed to. If you mean timber frame panel house manufacturers with prefab house suppliers, then service phases 1 to 4 are already way too far; instead, you better go to them after service phase 2 and fiddle with your architect at the same time as the house manufacturer continues to work on the scope of work specification.

I wish that builders, like when buying a car, could put everything together on the internet, see the price, and then order the house. No idea why that is not done or should be done. Just click, click, click,

This transfer of the new car configurator would be the perfect way to "Maggi fix sauce for Tuscan-style houses and other McMansion hells". The software development costs alone for not being able to combine moss-green velour carpet with the chocolate-brown leather steering wheel can only be recouped with a high-volume product—there the Golf basically has to cross-subsidize the A8 :)

As long as you only want to make changes inside it’s okay, but if you want to make changes to width/length yourself, it gets really expensive quickly.

For that, check out "Changing a floor plan’s size"; I have explained this in detail there.

I politely ask the group, why should the architect carry out a single contract award?

Surely that can be done by oneself. The architect creates the project and, as the person authorized to submit building applications, submits the documents to the building authority. After that, the client receives their building permit and can do whatever they want.

Then you go to the civil engineer, the structural engineer, the carpenter, and the roofer.