Garage as smooth wall (steel sheet) or timber frame construction

Metal naturally expands when heated, so the whole thing moves. Metal, of course, does not absorb any moisture, but it can allow it to condense wonderfully. Without appropriate interior cladding, the inside can easily turn into a dripstone cave. That’s why carport sheet metal roofs usually have a felt layer glued underneath.

Metal can of course be protected against the weather by various methods. The easiest would probably be hot-dip galvanizing (electro-galvanizing is actually not enough for permanent outdoor exposure in the rain). You can also powder coat it. Both processes have the disadvantage that chips or even just scratches down to the metal inevitably attract rust (or require reworking).
There are also stainless steels, more precisely V2A and V4A. (1.4301 / 1.4571 and similar). V2A is theoretically good for outdoor use but not permanently good enough. Most door handles are made of V2A. Surface rust tends to form on it.
If you want to do it really cool, you use V4A. It is seawater resistant and won’t rot away in 5,000 years. Unfortunately, for laypeople, it is not affordable.

Let’s cut it short:

- Hot-dip galvanizing is inexpensive and durable but doesn’t look very nice.
- Powder coating is a bit more expensive, but you get the metal in any color. As long as the coating is intact everywhere, it will hold up.

The annoying thing about metal is that after a few years, surface repairs are much harder than, for example, wood. You can sand the old layer on (or off) wood and paint over it. Removing the old layer from metal is no less difficult with powder coating in the garden, haha, or with hot-dip galvanizing. And spray cans on large surfaces are botched work.

But I think the prefabricated garage suppliers certainly have ways to rework their surfaces somehow.
A carport is more open; air constantly flows through. Less moisture forms than in a sealed garage.

Acquaintances of ours have a steel garage that is over 10 years old. So far, there have been no problems there. They decided against the additional costs for the roof coating/-fleece at the time. Allegedly, only on a few days of the year and only under very special weather conditions could a drop be detected on the cars. Since we did not have 6m width for a double garage and based on the experience of the acquaintances, we also decided on a steel garage measuring 5.40 x 9m two years ago. However, we ordered the roof coating. So far, I can't say much negative either. The only thing is that the fastening options are certainly better on a wooden or concrete garage and the temperature issue mentioned by . For fastening, you either have to rely on the systems offered by the manufacturer, which in my opinion are very expensive, or you have to be creative and build something yourself.

: Thanks for the post. Could we exchange information bilaterally regarding providers, photos, experience?

Ok, and how? I thought I could click on you directly via your username and message you; but it doesn't work. Sorry, I'm new here in the forum. Or can you message me?

I wrote you a message. It can be found at the top right under the menu item [Unterhaltung].

So far, I can't say much negative either.
The only thing is that the attachment options are certainly better on a wooden or concrete garage, as well as the temperature issue mentioned by .
For attachment, you either have to rely on the systems offered by the manufacturer, which in my opinion are very expensive, or you get creative and build something yourself.

Could you please explain a bit more about the temperature issue?

For example, if it gets very hot in summer, does the car inside the garage heat up just as much as if it were standing in the sun?

And can't some relief be provided if the garage door is left slightly open (or more) and a garage window is kept open?

But in winter, the car windows shouldn't fog up, right?