Feasibility financing for new construction

Demand:

[*]What is the market value of the land and house after completion? 1.1 - 1.3 million
[*]Total costs: €828,000

Where does the difference of €300,000 to €500,000 between value and costs come from?

Do I understand correctly that you want to demolish a terraced mid-terrace house and build a new one in the gap? Are the additional costs for securing and documenting the neighboring houses included? The demolition is also likely to be more expensive than a standard demolition.

For your information: I have already asked two questions regarding floor plans here in another subforum under a different account, but for some reason I can no longer log in and cannot change the password either.

The thing with the backyard seemed somewhat familiar to me. A link is helpful!
https://www.hausbau-forum.de/threads/grundriss-mit-einschraenkungen-fuer-stadthaus-rmh-fuer-familie.42312/

With 2% repayment, the loan will run several years into retirement. What is the plan here?

Well, good question... either sell and downsize or also invest the upcoming inheritance (approx. 200-300K€)...

Question:

Where does the difference of 300 to 500,000€ in value and costs come from?

I understood the question as what proceeds can be achieved from a sale. Currently, the offers are, as said, between 1.1 and 1.3 million for small terraced houses or semi-detached houses. Therefore, the difference would probably be classified as profit if one sold after construction.

Do I understand correctly that you want to demolish a mid-terrace house and build a new one in the gap? Are the additional costs for securing and documenting the neighboring houses accounted for? The demolition is likely to be more expensive than a standard demolition as well.

Yes, exactly. So the neighboring buildings are significantly younger and currently it is rather the other way around, and the neighboring buildings support my old house. There is no direct connection to the left neighbor (approx. 1.5m distance and about 3m offset forward at the front). My house is attached to the right neighbor. Supporting will not be necessary there. If we were to build with a basement, underpinning or similar would have been necessary, but we have already cancelled the basement partly for this reason. However, I have not yet precisely inquired about the demolition costs and simply estimated 25K€.

The backyard thing seemed somewhat familiar to me. A link is helpful!
https://www.hausbau-forum.de/threads/grundriss-mit-einschraenkungen-fuer-stadthaus-rmh-fuer-familie.42312/

Thanks for the link...

Demand: Where does the difference of 300 to 500,000€ in value and costs come from?

I can well imagine that the house has such a value. I doubt whether you can build 200 sqm with this budget.

Demolition of a single-family house I know at 200€/sqm.
That should be significantly higher for a [REH], because you have to work much more precisely and carefully...