Using House Wrap Under Metal Roof Over Perlins

Metal roof purlins are installed horizontally under metal roofs.

Using house wrap under metal roof over perlins.

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. 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. The roof is an important element of the building envelope. One of the more popular methods of placing metal roofing on a home is to lay down purlins across the existing shingles.

The spacing of your purlins depends on the expected snow and wind load. I ve seen instances where people have applied house wrap directly between roof purlins and roof steel in an effort to control condensation. Taking care of your building envelope. Can a metal roof be installed over my existing shingles without the use of battens.

Thanks edward for allowing me to share our correspondence on this frequently asked question. In this case simply lay the insulation between the purlins. 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. 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.

It needs to be addressed with the utmost care and consideration. House wrap is quite permeable. Make sure that the insulation you are using is the same thickness so that the metal roof will fit better. Tips on installing purlins for your metal roofing project.

You will typically see purlins used for re roof project over existing shingles or other situations. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. 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.