Insulate Metal Roof Over Purlins

How to insulate a metal building.

Insulate metal roof over purlins.

Roof wall new install over 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. When fiberglass batts are installed in unvented bays the batts allow moist indoor air to reach the cold steel roofing or sheathing. Factory pre cut white vinyl faced fiber glass blankets are placed in between the metal roof purlins and held in place by steel strapping called banding screwed to the bottom of the purlin.

This is by far the most common way to install a metal roof. The batts are located side to side on the rafter of the roof. As long as the plywood under the shingle roof is in good condition this way can provide many benefits. Stand off roof clips are fastened to the top of the purlins using self drilling fasteners and the metal roof panels are attached to the stand off clip creating slightly more space above the purlin.

It gets more complicated when you look at adding the foam into the equation. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Both materials make a great physical barrier between the interior building and the metal roof. We do recommend it however.

Apply double sided tape on the top of purlins helps keep the insulation from blowing in the wind. A thermal spacer block is typically recommended depending on the stand off distance and the amount of insulation draped over the purlins. Make sure that the insulation you are using is the same thickness so that the metal roof will fit better. Your roof purlin spacing can vary but 5 on center and 8 inches in depth is common which is the available insulating area.

One of the more popular methods of placing metal roofing on a home is to lay down purlins across the existing shingles. The code restrictions on the use of air permeable insulation between purlins were developed to prevent the purlins or roof sheathing from rotting. 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. The most common material used for an insulating metal roof is fiberglass batts or glass mineral wool.

Fiberglass batts or glass mineral wool metal roof insulation. I am installing ribbed metal panels over a singlt slope roof on a new workshop. You ve got the metal the foam and the interaction between them to consider. I was planning to install directly over 2x4 purlins which are mostly already installed.

Do all roofing projects require purlins. The system of installing metal roofing over the trusses or over purlins is typical.