Hello!

I live in Toronto Canada and am planning a 12×16 shed build for a woodworking shop. I would like to use the shop year round. I have been researching how to insulate the floor and would like some feedback on my plan…

2×6 joists with a 1.5-2″ layer of EPS rigid insulation on the underside, so I can fill the joist bays with a fluffy insulation. The EPS insulation would be sitting on top of a concrete paver / gravel base. I would use spray foam or polyurethane to seal up the subfloor/joists/EPS layers. Hopefully this would create a good air barrier.

1. Is it OK to rest the joists directly onto the EPS, or would it compress the insulation over time? I might consider a layer of 3/8″ OSB between the joist and EPS to address this – would that impact the effect of the rigid insulation?

2. Is it recommended to cover the exposed sides of the EPS? I would extend the wall sheathing to cover the sides unless there is a better solution

3. Would there be any issues with moisture/ventilation because the EPS is sitting directly on the pavers? Essentially no airflow on the underside of the shed.

4. Is it enough to use polyurethane adhesive to secure the EPS to the joists, or are additional mechanical fasteners recommended?

Thanks for reading and providing input