Installing Vapor Barrier Under Metal Roof

I am planning to install a 29 ga metal roof on my new 2 story garage office.

Installing vapor barrier under metal roof.

It serves as a moisture barrier as well as a slip sheet. As long as the plywood under the shingle roof is in good condition this way can provide many benefits. What type of vapor barrier should i use unser the roof above the sleepers. In a low slope roof assembly the vapor retarder is normally installed under the primary roof insulation.

This type of underlayment is critical to a quality roof installation. The asphalt in the felt paper is waterproof and does a great job of protecting the. Put the steel down directly on a vapor barrier. Metal roofs must be laid flat on a vapor barrier because steel will condensate if there s any air space underneath it.

I am installing it on 2 x4 sleepers at 16 o c. It doesn t matter if the air space is a half inch or six inches because the condensation factor will remain the same. The best underlayment for metal roofs. Traditionally metal roofs have used standard 30 pound felt paper underlayment.

3 install 1x4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1x4 purlins over the shingle roof. This is by far the most common way to install a metal roof. Make sure the product is designed to be used under metal. Underlayment must also act as a secondary weather barrier in case the roof fails.

The cavity under the sleepers is 9 1 4 and it will be insulated and finished with wallboard. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. 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. 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.

Most metal roof companies recommend installing felt paper on roof sheathing before you install the metal roofing.