Installing Vapor Barrier Under Metal Roof

This is by far the most common way to install a metal roof.

Installing vapor barrier under metal roof.

Metal roofs must be laid flat on a vapor barrier because steel will condensate if there s any air space underneath it. In a low slope roof assembly the vapor retarder is normally installed under the primary roof insulation. The asphalt in the felt paper is waterproof and does a great job of protecting the. I am installing it on 2 x4 sleepers at 16 o c.

It serves as a moisture barrier as well as a slip sheet. Therefore one will often see it installed directly on a roof deck such as a concrete or wood deck or on a continuous substrate such as gypsum board or wood panels that is installed directly over a metal deck. Make sure the product is designed to be used under metal. What type of vapor barrier should i use unser the roof above the sleepers.

The cavity under the sleepers is 9 1 4 and it will be insulated and finished with wallboard. We recommend a polypropylene scrim reinforced underlayment made up of multiple layers. Several considerations must be addressed in the roofing system design including ensuring that the four barriers needed in any building enclosure i e water barrier thermal insulation barrier vapor retarder and air barrier are provided and are in the correct location for a given climate. As long as the plywood under the shingle roof is in good condition this way can provide many benefits.

Underlayment must also act as a secondary weather barrier in case the roof fails. Most metal roof companies recommend installing felt paper on roof sheathing before you install the metal roofing. 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.

I am planning to install a 29 ga metal roof on my new 2 story garage office. It doesn t matter if the air space is a half inch or six inches because the condensation factor will remain the same. This type of underlayment is critical to a quality roof installation. The best underlayment for metal roofs.

Build your structure where possible in an elevated position with good natural drainage place a vapor retarder under floor gravel or concrete ventilate enclosed building when concrete is being poured and continue to ventilate until it is cured use heaters that are vented to the.