Bank does not accept own contribution

Your problem is that the equivalent value still needs to be created with you and is not already there. We renovated existing properties and needed €200,000 from the bank. Since there was no mortgage on the house and it was already valued by the bank at €300,000 without renovation and expansion, we did not have to provide an itemized list or invoices. The bank paid us the money in a lump sum at the desired time. So it is possible for the bank to pay the money in a lump sum, but of course only if there are corresponding (unencumbered) values to back it up.

I have watched enough episodes of "die Schnäppchenhäuser" to write off the project as unfeasible :-P

Who wrote that, show me? Of course you need an invoice! There are even release limits for transfers which the bank has to manually lift for high transfers. So I built with individual trades and that is already close to how you want to build, compared to someone who builds according to a payment plan with 5-10 payments. Here it can of course be different with a general contractor.

So if this is problematic for you, then the idea is almost over here.

I only know the possibility of payment without proof with very solvent customers.

Here:

Not that we are talking past each other. I understand that the bank wants to see an invoice to release money. The question is whether they want to see invoices from specialized companies to make sure the construction was carried out professionally. In the latter case, of course, I can't provide anything. For the payment of the amounts, I naturally have invoices for materials.

I have seen enough episodes of "die Schnäppchenhäuser" to dismiss the project as unfeasible

We hope that the OP will not be on the show "Baupfusch - Familie in Not" in a few years. I keep my fingers crossed, but remain skeptical.

We had informed ourselves there. When it comes to the floor plans, you are limited and have read many negative reports about companies. There are shell houses where the interior finishing (that is heating etc.) has to be ordered as well, and again you are restricted.

Plan B: Then you have not informed yourself sufficiently! We have researched many company profiles in the area of timber frame construction and not all, but some, offer, besides turnkey and technically finished (or whatever they call it), also a shell house. Then exterior and statically relevant interior walls come without insulation, so open to the inside but including windows/roller shutters and a covered roof. That means 2 days on the construction site for the builder and then they leave again. However, many also deliver, for example, insulation material, drywall panels, instructions, and more.

What might make it more attractive for the bank is that it is an established concept of a construction company and all calculations, plans, etc., are from this company.

The company will then ideally accept the foundation slab or insist on an expert report before placing the house on it, and then you already have a basis. Then the bank knows what it receives at a minimum "as collateral value."

Then comes your listing with the help of the architect for all trades: sanitary, electrical, heating/ventilation, screed, drywall, stairs, floor coverings, walls, exterior plaster, outdoor facilities ... you give the complete list to the bank in two columns: offer from the company preferably specifying material & labor costs separately and next to it the cost savings through DIY = only the labor!

And the material costs that are still open can ideally also be covered largely from equity.

Your problem is that the equivalent value still has to be created with you and is not already there. We renovated existing property and needed €200,000 from the bank. Since there was no mortgage on the house and it was valued by the bank at €300,000 without renovation and expansion, we did not have to provide a statement or any invoices. The bank paid us the money in a lump sum at the requested time. So it is possible that the bank pays the money in one lump sum but of course only if corresponding (unencumbered) values stand behind it.

Thank you for the experience report! I don’t need a lump sum payout. It’s enough for me if the bank does not require invoices from specialist companies. All invoices for materials are, of course, available.