No Sheathing Under Metal Roof

July 28 2017.

No sheathing under metal roof. Mike the pole barn guru. If you re wondering how to prevent condensation under a metal roof you re not alone. Owners of agricultural buildings man caves and horse barns all are worried about the corrosive effects of condensation. Traditionally metal roofs have used standard 30 pound felt paper underlayment.

The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. 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. It will help you to eliminate problems that may come when the house becomes extremely cold in the winter and terribly hot in the summer. Underlayment must also act as a secondary weather barrier in case the roof fails.

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. The best underlayment for metal roofs. 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. 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.

Then the top of all your purlins once osb under metal roof panels is placed will be in the same plane and the roof steel will lay flat. For many applications a layer of plywood underneath your metal roofing is an unnecessary expense. Polyurethane spray foam metal roof insulation. 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.

How to prevent condensation under a metal roof.