ᐅ Masonry Garage – Should You Insulate a Flat Roof or Not?

Hello everyone,

I have a question regarding a self-built garage. We plan to build it soon. Our garage will be attached directly to our house and separated from it by a T30 fire-rated door.
According to the floor plan, it should be built entirely from 17.5 cm (7 inches) hollow bricks and will have a wooden flat roof. The garage would then be uninsulated, so my question is whether it should be insulated.
I’ve found many different opinions online.
My current understanding is that at least the roof should be insulated.

I’m curious how your garages were constructed. Do you have additional insulation on the outside? If you also have a wooden flat roof, was it insulated from below or above?

Thanks in advance for your feedback.

Hello

Garage / workshop as a timber frame structure with a flat roof.
Walls are timber studs, 24 cm (9.5 inches) insulated with 60 mm (2.4 inches) wood fiber insulation boards.
Roof rafters insulated with 30 cm (12 inches) insulation.
Concrete floor with underfloor heating.

Olli

wrobel schrieb:
Hello

Garage / workshop as a timber frame construction with a flat roof.
Walls: 24 cm (9.5 inches) stud framework insulated, plus 60 mm (2.4 inches) wood fiber insulation boards.
Roof: roof beams insulated with 30 cm (12 inches) insulation.
Concrete floor with underfloor heating.



Olli

This building method is probably rather unusual for a garage. But it definitely makes sense for a workshop. Some timber frame houses are not insulated as well....

For an uninsulated garage roof, there can be issues with condensation. If the roof is the coldest part, water will condense there and then drip down. However, in general, a garage does not necessarily need to be insulated.

Tentakel schrieb:
With an uninsulated garage roof, you can have "problems" with condensation. If the roof is the coldest part, water will condense there and then drip down. But basically, a garage doesn’t necessarily have to be insulated.

On the contrary. In an insulated garage, you can have issues with condensation in summer if you don't ventilate properly. An uninsulated garage with good ventilation is actually the safest design.

Ours is insulated, however. A flat roof insulated from the inside is quite a complex and error-prone construction. This definitely needs to be taken into account during the planning phase and, in my opinion, is not a DIY project.

Heated garages are, as far as I know, legally problematic in terms of building codes.