Questions about renovation, building authority

Good morning everyone,
I hope someone can help me out a bit here, I’m a bit stuck... The following issue:
My mother and her sister inherited a house after my grandma passed away, my aunt lives on the ground floor of this house, the upper floor is still empty. Now the idea came up that I could convert the upper floor into an apartment, it is finished, but the electrical installation is completely connected to the ground floor, water and sewage are completely missing... So the upper floor needs to be completely renovated. My main question now is, if I build a fully-fledged second apartment in the upper floor, do I have to report anything to the building authority, the exterior remains untouched so no additional windows/ dormers, etc. Just the interior conversion to the apartment.
I look forward to your answers
Best regards
Andi

You only have to report it if the development plan contains regulations regarding the number of separate apartments (search for the keyword Wohneinheit in the development plan = Wohneinheit). If only one apartment per building structure is allowed, the two apartments may not be completely separated. Furthermore, there may be requirements regarding the maximum number of square meters a building can have. If I were you, I would simply call the responsible building authority (the municipality) and explain your concern. The ladies and gentlemen there usually help well and gladly.

All right, thank you very much for the quick response, then I will better inform myself about it again :)

Hello Andi,

So the top floor needs to be completely renovated. My main question now is, if I build a full second apartment on the upper floor, do I have to report anything to the building authority? The exterior shell remains unchanged, so no additional windows/dormers etc. Just the interior fit-out to make it an apartment.

I would recommend that you take the step to go to your responsible building authority. You are changing the status quo of the single-family house into a two-family house. This completely changes the existing building structure, possibly also affects the statics/fire protection of the house; aside from the fact that a two-family house is subject to different requirements than a simple single-family house.

Therefore, I would not be surprised if you have to apply for a permit ;)

Rhineland regards

Hello Andi,

is right. If you interpret your wording "full-fledged 2nd apartment" to mean that the upper floor is separated from the ground floor by an apartment entrance door, so that both parts could later be rented out separately or possibly even sold, this amounts to the so-called certificate of separation. Apart from the fact that this is probably desired/sensible from a practical point of view, this separation also brings other advantages; if desired, one can form individual ownership for the separate apartments in the land register, then encumber the apartments individually and/or allocate costs (for tax purposes) to the individual apartments.

If you want to pursue this consequence and take advantage of the benefits, you should, as Bauexperte suggested, sit down with the building authority and the AR right away so that all concerns such as soundproofing, separation, fire protection, escape routes, parking spaces, etc. are taken into account.

Regardless of what the development plan says regarding the number of residential units - it is fundamentally legitimate and by no means hopeless to submit a building application that deviates from the basic provisions of the development plan.

Best regards

thank you very much for the info!! Now I'm a bit wiser after all ;) then I'll head over to the [Bauamt] ^^