Do You Need Plywood Under Metal Siding

It adds insulation waterproofing and structural support for the framing.

Do you need plywood under metal siding.

Metal roofing requires a solid substrate. No the purposes of the plywood roof decking are to give lateral stability to the rafters trusses and create a walking surface. Rotted sagging areas in your roof s plywood decking should be replaced prior to installing metal panels in order to prevent costly repairs in the future. For many applications a layer of plywood underneath your metal roofing is an unnecessary expense.

1 you said some metal roofing should never have firring strips i have certainly seen that with some of the very thin steel or weak aluminum decking which could never stand even a foot of free span over firring strips without crumpling buckling under someone walking on it so they would have to lie flat on the water barrier over the sheathing. It depends if you need the shed heated for any thing if not no you do not need a plywood layer. Metal roofing should serve both these purposes i m. Plywood cabinets the wood that goes under residential siding exterior sheathing performs several functions.

Ensure that the plywood deck is strong enough to withstand the added weight of the metal panels.