Osb Under Metal Roof

Using nominal lumber 1x horizontal underneath and 2x vertical.

Osb under metal roof.

1 some metal roofs will be more likely than others to telegraph any unevenness of the surface beneath them. Cross purlin designs with 16 oc are sometimes called for. 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. Metal should be installed using a cold roof design so the typical metal assembly would be.

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

Allen a couple of things to consider. April 3 2017 filed under. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. 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.

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. Osb is widely used as roof decking material. Screws will do better than nails. The best underlayment for metal roofs.