Garage extension made of wood or solid? How did you build it?

We would like to build (have built – due to the size of 50m2 and the associated statics) a garage adapted to the house. The idea is to be able to come into the house dry and to gain parking space. Two quiet sectional or roller doors are to be installed at the front. The concealed corner on the left here should remain open for easy access to the garden gate, and a door at the back right leads into the garden. Since we do not want to intervene in the ETICS, the garage should be free-standing.


We have thought for some time about simply having a carport built and then neatly clad with wood. We have already received an offer from a company for this. Meanwhile, after some conversations, we would now prefer a solid approach, i.e., to build the outer wall with bricks and keep the wooden supports along the house. As a sketch, blue is the wall, boxes are wooden supports:


Now we have quite a few questions:

Walls: Wood or stone? We would like to plaster the garage like the house right away; the company suggested plasterable OSB boards here. However, wood requires much more maintenance, offers hardly any soundproofing, and cannot rest on the ground (it gets very windy here).

Floor: Paving or concrete slab? We could have paving done for about €75/m2. Is a concrete slab comparable? What advantages does each offer? Elsewhere, we had paving that tended to get damp.

Ceiling: In the original plan, we had intended polycarbonate panels with a frosted glass look: nice and bright but opaque. Is there anything speaking against this, e.g., complicated cleaning in case of moss or similar?

Our total budget is unfortunately not very large at €18k but would suffice for the wooden construction, paving, and the mentioned polycarbonate roof. Only – will one be happy with such a solution? How did you do it?

Do you manage with 18K€ on the first offer?

Personally, I find stone on stone much better, but that is also a matter of belief.

If the garage is to be plastered, it is somewhat easier with masonry, of course; I would not plaster on OSB, I would at least use other (diffusion-open) plaster carriers.

I also believe that nothing beats a proper foundation slab, especially since 75€/m² paving is quite expensive (unless it is a special stone)!

I can’t get anything out of the poly sheets anymore either; depending on the location, they tend to turn green quickly, and from experience, I can say that after a heavy hailstorm -> you have 30 million little fragments.

I personally would have a classic foundation slab built, brick with calcium silicate blocks (possibly 4DF 115) + plastering, and on top a bitumen roof with wooden construction.

So I would just go for a carport if that one gap is going to stay open anyway. The advantage of a garage is either burglary protection or frost-free. And you only have both if it is sealed. But it isn’t with you guys, so why build big walls and stuff? Paving, a proper carport, and that’s that.

Can you manage with 18K€ on the first offer?

Yes, including everything, so complete floor base and construction, roof and walls. Only the plastering is still missing. I’m maybe calculating with about 20k€ in total.

If the garage is to be plastered, that’s a bit easier with masonry, I wouldn’t plaster OSB, at least I would use other (breathable) plaster carriers.

I asked again because I couldn’t quite imagine it either. They are 22mm thick, impregnated OSB boards, on which 20mm of Styrofoam, reinforcing mesh and plaster will be applied. That’s how it would be done on other annexes and e.g. with timber frame construction as well.

Also, I believe nothing beats a proper floor slab, especially since 75€/m² paving is quite steep (unless that’s a special stone)!

Even just normal rectangular paving, but we can still get other offers. But including complete subsoil and thus basically replacement of the ground.
I also prefer a floor slab, mainly because of cleaning, but since our ground conduit for the heat pump and the rainwater pipes run underneath, it might be better in case of emergency to just remove a few stones instead of breaking up the floor slab. Right?

I can’t get excited about the poly boards anymore either, depending on location they tend to turn green quickly and from experience I can say that after a strong hailstorm -> 30 million little fun parts.

The turning green is also our biggest concern. With waterproofing membrane we would be about 1000€ cheaper, so it would really be an alternative the longer I think about it.
I wouldn’t have thought about hail for that (the boards are 16mm thick).

Personally, I would have a classic floor slab constructed, build and plaster with calcium silicate blocks (possibly 4DF 115) and on top a bitumen roof with a wooden frame.

What kind of company do I ask for that? Carpenters and masons each do only part of the work...

Well, if that gap is going to stay open anyway, I’d just take a carport.
The advantage of a garage is either burglary protection or frost-free conditions. And you only have both if it’s sealed airtight.
But since it isn’t with you, why bother building a lot of walls?

Pave it, get a proper carport, and that’s it.

Maybe, if it annoys us, we’ll put a door there, but for now we’ll leave it open. Burglary “protection” is provided by complete fencing of the property. It’s not only for the cars, but also for other stuff you want to store dry.