In this post, we will be going over the importance of properly staggering your base sheets in a multi-ply system. Follow our detailed guide to using properly staggered plies, focusing on a three-ply system.
When installing any multi-ply roofing system, it’s essential to make sure that you’re properly staggering the side laps of your roofing membranes. This prevents them from falling on top of one another, which can create a ponding water condition.
Ponding water can damage any roof by adding weight to create physical stress on the system or ice in colder environments. Ponding can also erode the material of the roofing system by encouraging the growth of algae and causing a build-up of debris and dirt.
Polyglass’s premium base sheets have convenient lay lines pre-printed on them, including the three and four-inch lines for the side laps, the 12 inch, the 18-5/8, and the other 12 inch lines. These markers assist with properly cutting membrane sheets to the appropriate width.
In this post, we will be going over the importance of properly staggering your base sheets in a multi-ply system. Follow our detailed guide to using properly staggered plies, focusing on a three-ply system.
How to install properly staggered plies
We’ll be using the example of a three-ply roofing system for this properly staggered plies installation guide, illustrated by Tim Leithead, a Polyschool trainer for Polyglass. This is one of Polyglass’s recommended ways of installing a three-ply system.
Step One: We’ve already installed our one-third base sheet and our full base sheets leading all the way up to the wall, extending one inch past the cap strip.
Step Two: Next, we will bring across our half sheet that we cut on our 18-5/8 inch line. Using this half sheet staggers the plies and gives us adequate space between each membrane layer. We’ll run all of these subsequent half sheets all the way up to the wall.
Step Three: Lay each base sheet membrane strip in place and then fold it in half along its length. Then pull off the protective film in a constant motion and lay the half of the sheet back down onto the roof. Remove the film on both sides of each strip.
Step Four: Once the layer is in place, go over all the seams with a hand roller to ensure they’ve fully adhered. Then, run over the whole roofing layer with an 80 lbs linoleum roller to ensure complete adhesion.
Step Five: Now, we’re going to install our final layer. We will use a full-width granulated cap sheet to form the third ply in this three-ply system. Again, we’ll extend this layer one inch past the cap strip. Repeat steps three and four to remove the film from the cap sheet and press it into place before ensuring adhesion using a roller.
Product Summary
Polybase V
Polybase V is an APP modified bitumen base sheet reinforced with a fiberglass mat for quality waterproofing and weathering protection. Polybase V sheets can be used as base ply or inter-ply layers in multi-ply low-sloped roofing systems. Polybase V sheets can be installed using either heat-welding or mechanical application.
Polyglass G2 Base
Polyglass G2 base sheets are made from fiberglass mat that has been coated with an oxidized asphalt blend. This helps to provide enhanced weathering protection and tear resistance to the membrane. Polyglass G2 base sheets can be used as effective base layers for multi-ply roofing systems.
Polyflex 5.0
Polyflex 5.0 cap sheets are polyester-reinforced APP membranes, featuring a premium plastomeric compound and non-woven polyester for exceptional durability. These cap sheets offer long-term weathering performance that resists factors like ponding. Polyflex 5.0 cap sheets are easy to install using heat-welding applications thanks to the burn-off film on the underside.