Shake Installation: Underlayment And Interlayment

Simulated Shake RoofingRoofs come in all shapes and sizes. They also differ in their durability and ability to keep the occupants of your establishment safe. This difference in safety offered by different lightweight roofing systems is graded as per ASTM standards. If you’ve bought DaVinci’s cedar shake alternative tiles, here are the different pre-installation underlayments and interlayments that your roofing contractor will need to be aware of:

Method 1
Class A Installation:
 Two layers of MB technologies TU-35 must be installed over the entire roof deck including areas with ice and water shield. No interlayment is required.

Cedar Roof Shingles
Method 2
Class A Installation:
Two layers of Fontana Vucaseal G4 must be installed over the entire roof deck including areas with ice and water shield. No interlayment is required.

Method 3
Class A Installation:
 In areas where ice and water shield is not installed the roof deck must be covered with 30 lb non-perforated asphalt saturated felt meeting requirements of ASTM D 226. Once the underlayment has been installed the roof must be covered with GAF Elk Versashield interlay. The Versashield should be cut into minimum 18" rolls and installed at the same exposure as the shakes. The felt should be applied over the top portion of the shakes and extend on to the plywood sheathing so that the bottom edge of the felt is positioned at a distance above the butt equal to twice the weather exposure. So, for an exposure of 9",start the next layer of felt 18" above the butt-line of the course below. (20" above the butt-line for a 10" exposure).

Method 4
Class C Installation:
Areas of the roof deck not covered by ice and watershield must be covered with 30 lb non-perforated asphalt saturated felt meeting requirements of ASTM D 226. In addition to the underlayment, roofs with slopes less than 6:12 must be covered with 18" 30 lb felt interlay. The felt should be applied over the top portion of the shakes and extend on to the plywood sheathing so that the bottom edge of the felt is positioned at a distance above the butt equal to twice the weather exposure. So, for an exposure of 9", start the next layer of felt 18" above the butt-line of the course below. (20" above the butt-line for a 10" exposure).

For more detailed explanations, refer to the Shake Installation Guide available on our website. If you have any queries about our products or the installation process, please reach out to us!


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