Osb Under Metal Roof

Metal should be installed using a cold roof design so the typical metal assembly would be.

Osb under metal roof.

Traditionally metal roofs have used standard 30 pound felt paper underlayment. April 3 2017 filed under. Underlayment must also act as a secondary weather barrier in case the roof fails. This case is most certainly the exception to the general rule and happens in far less than 5 of all post frame buildings.

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. The only reason to put osb on a roof would be in the case of a very narrow very long very tall building with high wind loads ones which would exceed the wind shear carrying capacity of the steel. Osb is widely used as roof decking material. Using nominal lumber 1x horizontal underneath and 2x vertical.

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. Screws will do better than nails. 1 metal 2 air space of 3 4 or greater using 1x4 or 2x4 purlins 3 wrb and 4 5 8 to 3 4 of ply or osb. The best underlayment for metal roofs.

2 fastener pull out all depends on the condition of the osb. Allen a couple of things to consider. 1 some metal roofs will be more likely than others to telegraph any unevenness of the surface beneath them. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material.