Hi fandango1
If you plan on doing engine-out work on the car:
9" hollows and 4" solids laid flat, both rendered externally are your best bet.
It would be an unusual builder who'd have problems with those.
They have been standard house construction in Dublin for years.
You'll need a padstone or bearing for the RSJ supporting the pulley.
Or you could go for a deluxe moveable beasty - you'll need a well laid slab.
If you plan on storing cars for long periods, or even on working for long periods or indeed spraying paint:
Insulating the walls is a logical step.
I suggest external insulation so it won't be damaged by work going on inside the garage.
This will allow you to securely fix benches, steel shelves or other equipment to the walls.
Be aware that the siting, external materials, size and height of the garage you can build without needing permission are all covered by the Planning Regulations.
If in doubt, you should take professional advise in relation to this.
FWIW
ONQ.
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