Prefabricated house vs. solid house - price difference?

What other details are needed to determine the slats? As a carpenter, I have built dozens of houses and never used others.

- regarding the slats - is there anything here that I should address? Or is it okay as it is now? To be honest, I wasn't really able to make sense of the previous answers.

Regarding the wall construction - for me, based on the references and the - what appears to be a favorable price - it is basically decided that I want to build with the contractor from whom I received the offer. (The architect is already planning accordingly). 42.5 cm stones with Lambda 0.09 would cost about €3,000 more. But I don’t know if I really want such thick walls - I will now think it over - especially whether the KFW loan is worth the additional effort / extra cost for me. You can also build energy-efficiently without a KFW loan.

I am also building in an area where the land prices (for our region) are relatively cheap. It is a bit outside in the countryside - I really like it, but a house can certainly be sold better later in the city, I’m not kidding myself about that! That’s why I don’t want to spend more than €350,000 for the entire construction project – with the current offer (the house will still be a bit bigger) that should work.

DIN 68800 and DIN 4074.

At least the planner must clear their throat very carefully.

But to return to the original question, as has already been said: Here apples have been compared with pears...

So thanks for all the information! Regarding the wall, I will definitely inquire about the additional costs for 42.5cm PP2/0.35! To be honest, I still haven’t quite figured out the roof battens – but I also haven’t read the standards. As far as I understand, it’s more or less a structural question – and whether you choose a slightly stronger roof and counter batten or not probably doesn't affect the price that much. (The decisive factor at this point is probably the labor time – but correct me if I’m wrong).

One shouldn’t possibly forget that so far this is only a "budget offer" – therefore nothing concrete. He has probably saved work here and there by not calculating everything more precisely and may have only copied some descriptions. (The same applies to the prefab house providers as well). I still can’t explain the price difference of up to €100,000. Besides, the question remains whether you really have to put a "Porsche" of a house on a "cheap plot" or whether the "Golf" model might also do. (You never know if you might want to sell again someday).

Regarding the construction project, I’m calculating €300,000 for the house anyway (including own work, affordable doors and windows, etc.) and €350,000 for the entire construction project. (A buffer of €20,000 is available – but should not be touched if possible, as there are still development costs to be paid later).

Oh man RoLi no Google? DIN 68800: untreated wood must be installed! Simply put: structural wood protection before chemical wood protection! Point 1. Exceptionally (!) impregnated wood may be used, but as mentioned, only exceptionally. As a builder, you must be given a reason why you are getting this stuff. DIN 4074: for 30/50 battens, sorting class S 10 is specified according to 4074. I have not yet seen impregnated battens in S 10, and I travel a lot in this country. Depending on the rafter spacing, even 40/60 are required (also in S 10). Of course, all these things are somewhat more expensive, since it is technically dried wood.

It is also stated like this in the roofer’s professional regulations, which the carpenter probably hasn’t read in a long time...