No Sheathing Under Roof

If you re wondering how to prevent condensation under a metal roof you re not alone.

No sheathing under roof.

Modern metal roofs are expected to last 30 years or longer. Here s how to fight back against the enemy within. Plywood has an r value of 1 25 and fiberglass batts have an r value of 3 14. Currently there is no sheathing or tar paper under the metal.

Never attach roof sheathing with staples. More effective insulation with r values ranging from 3 6 to 8 0 rigid foam sheathing has much better insulation per inch than other materials i e. While metal roofing doesn t require plywood underlayment there are circumstances in which you may wish to install plywood to anticipate future roofing needs or to offer additional soundproofing. Sheathing is installed perpendicular to roof trusses.

Roof sheathing comes in grid marked 4 by 8 foot sheets and should be installed perpendicular to the frame. A leak free roof membrane that is fully adhered to the roof sheathing should be installed. The current state and local building codes for the minimum r value of air impermeable insulation required for the roof assemblies in the home s climate. 3 benefits of rigid foam sheathing.

Sheathing should be a minimum of 19 32 inch thick. When open cell spray foam is used a low perm class ii vapor retarder is installed where required. It is nailed directly to the rafters. How to prevent condensation under a metal roof.

July 28 2017.