Metal Roof Installed Over Purlins

For many applications a layer of plywood underneath your metal roofing is an unnecessary expense.

Metal roof installed over purlins.

Choosing to install a metal roof this way can save you some dough and garner all of the benefits of a metal roof in the humid climate of florida. Flashing is metal trim that fits over joints where two sections of roof meet. Metal roof purlins are installed horizontally under metal roofs. The second way to install a metal roof over a shingle roof is with the use of purlins or battens.

I have been playing around with the ribbed metal roof but pricing is pretty high over shingles obviously. Doesn t provide the flattest surface for the metal roofing to be installed over each course of shingles is about a 1 8 higher than the course just below it. The purlins are screwed or nailed down to the roof deck depending on how the metal roofing manufacture has testing for their roofing panels and then the metal is installed to the purlins. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern.

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. I was driving by a new building being constructed and it has wood trusses with 2x4 horizontal purlins looks to be about 2 oc spacing on the trusses. 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. A metal roof can be installed over a shingle roof but you ll need to make sure the plywood under your shingle roof is in good enough shape to handle a new metal roof over top.

It helps direct water away from the meeting points and keeps the roofing dry. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Purlins are 2 by 4 feet and are installed much like metal roofing. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

The flashing should overlap the edge of the roof by one inch to help direct water.