Using House Wrap Under Metal Roof Over Perlins

Tips on installing purlins for your metal roofing project.

Using house wrap under metal roof over perlins.

For new construction florida building code does not require the use of a purlin system and some profiles like our tcm loc panel does not require use of purlins. Taking care of your building envelope. Make sure that the insulation you are using is the same thickness so that the metal roof will fit better. The spacing of your purlins depends on the expected snow and wind load.

They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Metal roof purlins are installed horizontally under metal roofs. Purlins are 2 by 4 feet and are installed much like metal roofing. This great question comes from edward c a homeowner who plans to have a new metal roof installed over the aging existing shingles on his single story home.

The roof is an important element of the building envelope. A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air water heat light and noise transfer. Any warm moist air which would rise to it will pass through to the underside of the roof steel and condense. One of the more popular methods of placing metal roofing on a home is to lay down purlins across the existing shingles.

You will typically see purlins used for re roof project over existing shingles or other situations. Can a metal roof be installed over my existing shingles without the use of battens. There are two ways to do this put in firring nailing though nails are not used any more for this strips or purlins in steel frame construction on the roof to support it or place the metal roofing directly on a flat surface like foam insulation board or the roof sheathing with roof water barrier in the correct position in the layer. Metal roofing panels rated for architectural use attached to purlins horizontal pieces of wood or metal fastened to roofing trusses are structurally sound when installed according to your roofing manufacturer s instructions and local building codes.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. In this case simply lay the insulation between the purlins. House wrap is quite permeable.