ᐅ Extension to a single-family house as a senior apartment, any ideas?

Frank-Ol schrieb:

My question is more about the technical construction aspect.

The technical construction aspect is the least of the problems.
- Has it already been checked whether the lot size allows for an extension?
- Is there a development plan / zoning restriction that might prohibit two residential units on one property?
- Are additional (two?) parking spaces possible on the property?
and so on.

Afterwards, consider the room layout (number of rooms, sizes, etc.).

Finally, look for an architect. An extension to an existing house requires an architect. Prefabricated house builders, etc., build houses but do not offer specific extensions from their catalog.
Who ultimately carries out the technical construction of the extension doesn’t matter—whether solid construction, timber frame, general contractor, individual tradespeople, etc.

We have been working on this project for almost three years. We want to build an extension or a small bungalow of no more than 80 sqm (860 sq ft) on our property for my mother-in-law. The initial idea was to convert an outbuilding. We have the permit (building permit / planning permission) for that, but renovating it would not be cost-effective due to legal requirements and would be more expensive than new construction given the difficult floor plan. This year, the idea of demolishing and rebuilding came up. So far, all affordable options have turned out to be surprisingly expensive. We always end up at a minimum of 2500 euros/sqm (232 USD/sq ft). The region is far enough from metropolitan fringe areas, so construction prices are not inflated. However, we had planned to build wheelchair accessible, which adds some additional square meters.

Since my mother-in-law will likely have a small pension, the construction would mean she would have to invest all her savings into the build, which could become problematic in the long term concerning the inheritance distribution among my wife’s siblings.

80-100m2 (860-1,075 sq ft) roughly requires an investment of 240,000-300,000. Can you manage that? Then proceed to the next step. This has already been outlined. We are happy to help.

Not at the moment, as we currently do not want/can rely on my employer. A generational change is upcoming. But theoretically, yes. So, we are planning a bit casually for now.