Convert garage into living space

I would like to convert my garage (70 sqm) into living space. The building currently consists of a 24cm masonry wall (cinder block from 1970) and an uninsulated ring beam; unfortunately, exterior insulation is not possible on three walls because the neighbors' walls are practically right next to them (1-3 cm air gap).

An internal insulation, as often advertised, with fiber boards and vapor barrier is out of the question.

What options do I have to convert the garage into living space? Is it possible to build another wall inside, possibly with 5 cm of mineral wool between the walls, and in that case, do I need to ventilate behind it?

I hope the explanations are understandable and thank you for the feedback!

Although I don’t understand why insulation is not possible on 3 walls (the building can have a maximum of 2 walls on the boundary), if interior insulation is not an option, it will be difficult. Building in a second wall is also an interior insulation that, of course, must be ventilated from behind. I would consult an expert who can evaluate this both structurally and energetically. It may well be possible, but it may also be that the building fabric is not suitable for residential use.

Sounds like the garage is on the boundary. Is it even allowed to convert it into living space, just as a silly counter-question?

Hello @Stefan_,

Alex85 is right - living spaces on the boundary or the conversion of a privileged, boundary-adjacent garage entails a building code issue. It can work in closed, inner-city development, but it should also be checked.

If your property is in a residential area with detached houses, it becomes problematic. In NRW, for example, it would be possible if you could secure all three sides by easement (setback easement) and the neighbors all only have privileged garages AND their own buildings in turn stand at least 3m further away from your easement, and no other building law violations exist/arise, i.e. the residential buildings of your neighbors would have to be at least 6m away from your garage on all three sides.

In addition, there is the question of cost, where I am not familiar with the situation in RP at this point, but it will not be cheap.

Best regards Dirk Grafe

Thank you very much for the feedback. The building actually stands with 3 walls on the boundary, therefore external insulation is not possible. The garage/barn is located within the town (plot ratio 1), closed, inner-city development. I am, of course, familiar with the setback limits, but I am very optimistic that I will be allowed to expand here. The legal question should not necessarily be the topic either. The building (only ground floor) corresponds to a shell from the 70s, i.e. foundations, floor slab, ring beam all dry and structurally sound. The roof will be redone. Is there perhaps an insulating brick that can be built from the inside, with ventilation if necessary? For the ventilation, holes would then have to be drilled into the outer wall? I have seen this once before in an old barn (rubble stones), where new masonry was done inside (with an air gap). Does anyone have experience with this?