Construction cost calculation single-family house architect without own work

But that's where the problem lies... You take as the base sum the offer from your brother-in-law, which probably already represents a pretty good price. You automatically transfer this good price to all other trades. Outdoor facilities are completely missing. A few bushes and lawn are not enough. The preliminary work is more complex and expensive. (Terrace, driveway, splash protection, walls on slopes, etc.) quickly amount to 20k and more. All this in EL is intense. I would also carefully consider whether I want to live at the construction site (from the outside) for 2 to 3 years.

I don't see any positions here that are properly calculated, and as for the wishes, you can safely forget about the 420k€.

You are both right.

Certainly a bit naive to scale up all trades like that. Our brother-in-law says he knows all the craftsmen very well, but personally I would still call the market price.

I have quickly adjusted my calculation. Tweaked a bit, adjusted percentage points, and removed the family offer.

As already said, the calculation comes from me and I am only beginning to engage with everything because I want to generate further opinions and images in addition to the architect's calculation. For me, this is also a process, although I previously thought I would just tell the architect what I want and especially what I am willing to pay, and he would then advise me. Wrong thinking.

Measured against what I am still willing to invest - where should we make cuts first?

(I find the Edition 600 from Viebrockhaus quite good, as it is price-transparent at 348k according to the February 2020 price list without garage, so roughly 390-400k with - or where is my error in thinking - but the client has always rejected this.)

One more thing: LPH 1 to 3 is not enough. Min LPH4 is still necessary, someone has to submit the application who is also authorized to do so. 5 could then come from a construction company. 6 and 7 are also extremely important in case of individual awarding, otherwise, who should handle the tendering of the trades? I would view self-inquiries very critically, after all, you want to avoid later price increases due to missing items in the offers as much as possible. As a layperson, you simply cannot keep track of it all that precisely and will inevitably face additional costs after the quotes. Without a bill of quantities, I would only conditionally trust the offers from the craftsmen...

We were clearly advised that we only needed the planning up to the building application. Our brother-in-law would take a look at the trades (small town, people know each other) and I would have brought in an expert for the acceptance.

I am currently doing the tender alongside and contacting all trades based on the drawing to get quotes. But whether they contain any clauses or what, I of course have to trust.

Edit: the architect is an acquaintance of ours and we agreed that we can activate him at any time for questions and problems regarding the services, also contractually.

2nd Edit: Basically, he is working with us up to phases 6-7. We are managing the construction together with him and our brother-in-law, who runs a local construction company. I must have mixed something up. But I am collecting all the offers and forwarding them to the architect for review.