Precast concrete double garage - workshop setup

[Majimoto]

Do you need to fix anything to the concrete ? You could build a free standing structure inside the concrete walls, each "wall" just wedged in position until the others are there to support it.. Here in France I would use the steel channels that are sold for dry lining with the insulation set in the channels. Something similar in wood should be possible.

I did something like that in my stone built barn, using moisture resistant chipboard rather than ply as the inner surface, it's cheaper than ply and just as practical to fix to. (The joist on top in this picture was because I had the headroom to add a mezanine).

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Delighted to see this photo. I was faced with exact similar situation but have used pallets to make the internal walls. Plastic sheeting against the walls, filled pallet spaces with insulation fibre, another sheet of plastic covering that, and finally OSB sheets as the final face. Good one