Metal Roof Over Purlins No Vapor Barrier

Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point.

Metal roof over purlins no vapor barrier.

In this installation the vapor barrier is installed on the side of the insulation nearest the interior of the building. In the old days we used to do 5 v metal roofs on 2x4 purlins with lead headed roofing nails and no sheathing. There is no need to roll a vapor barrier over purlins and then seal with tape which can reduce labor hours and cost. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof.

A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system. The problem with using. Metal roof purlins are installed horizontally under metal roofs. Available systems include a patented frame less metal over metal recover option that provides a low cost retrofit solution over existing exposed fastened panels with ribs up to 1 5 tall.

Mcelroy metal has develop several methods to recover an existing metal roof using the symmetrical 238t standing seam roof system. When using plywood nail it directly to the purlins and screw the metal roofing panels through the plywood into the purlins as instructed by the manufacturer. Hmm i am thinking that this will not be an issue due to having a sound vapor barrier on the warm side of the roof. That reduction of air and moisture infiltration can then help improve roof longevity.

The rubber backer on the material helps protect the back side of the panel from corrosion although there is no protection at the panel s cut edges. But a preinstalled membrane may be even more effective at removing condensation. This is by far the most common way to install a metal roof. Hi just trying to put the finishing touches on the plans for a very small 12x16 cabin and am unsure about the best way to install the metal roof.

238t recover systems provide a long term solution to existing exposed. Purlins are 2 by 4 feet and are installed much like metal roofing. I ll never forget seeing wind blown snow a quarter to a half inch thick on the attic insulation after one storm. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. As long as the plywood under the shingle roof is in good condition this way can provide many benefits.