No Sheathing Under Metal Roof

The best underlayment for metal roofs.

No sheathing under metal roof.

In order to add moisture barrier under metal roof you can spray the undersides of the roof by using a thick layer of polyurethane spray foam. Traditionally metal roofs have used standard 30 pound felt paper underlayment. How to prevent condensation under a metal roof. Metal roofing panels rated for architectural use attached to purlins horizontal pieces of wood or metal fastened to roofing trusses are structurally sound when installed according to your roofing manufacturer s instructions and local building codes.

My understanding is that with metal roofing you absolutely have to have a drainage plain. For many applications a layer of plywood underneath your metal roofing is an unnecessary expense. If you re wondering how to prevent condensation under a metal roof you re not alone. Underlayment must also act as a secondary weather barrier in case the roof fails.

If your home s existing shingles are pretty curled you could install a textured metal roof such as a metal shingle shake or tile directly over the curled shingles along with underlayment. This would mean a plywood deck with some sort of building paper to handle the inevitable condensation that forms on the underside of the roofing. In order to avoid a hump at the transition from two layers of materials to one the notation on the building plans advises to lower the roof purlins in these areas by 7 16. Here s how to fight back against the enemy within.

You also could install a corrugated through fastened metal roofing product and probably not have issues. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. Owners of agricultural buildings man caves and horse barns all are worried about the corrosive effects of condensation. July 28 2017.

Polyurethane spray foam metal roof insulation.