Minimum EPS density (compressive strength) for roof/wall external sheathing
Do you know if it would be possible to use low density EPS on top of a roof sheathing?
I suppose the critical thing here is the EPS being able to support either the plywood, OSB or 2×4’s that lie over it. In other words, we need a minimal compressive strength .
I would bet that with plywood or OSB you would not have any problem using any low density EPS, because the force exerted by the roofing weight is spread through all of the plywood/OSB board’s area, but if you use 2×4’s spaced 24 inches on center, to hold the rigid foam and nail, for example, a metal roofing over it, I’m not sure that a low density EPS will hold without being squeezed by the 2×4’s holding the weight of the roof.
I think the lowest density you guys get in the US is Type I, which is 1 pcf. But here in Chile the cheapest and most commonly used EPS is 0.62 pcf.
Do you think a 0.62 pcf EPS would be ok using 2×4”s on a light metal roof? (I think we are talking of a compressive strength near 4 psi)
Would you recommend a higher density EPS?
What about a wall? what compressive strength would I need for an external EPS insulation sheathing installed with bolts, 1×4″ furrings, and holding wood siding?