When installing a steep-slope roofing system, there are several roofing details to consider. These vary from wall flashing to roof penetrations and valleys.
But before installing any of these details, you’ll need a stable foundation from which to work. This is provided by the roof field, which typically consists of a layer of underlayment. This layer is installed either on top of or underneath the other roofing details to provide a waterproof layer of protection.
Our steep-slope roof field detail installation guide uses Polystick® TU Plus underlayment and adhesive materials such as Polyglass PG 500 modified cement.
How to install steep slope roof field details
- Step One: Before beginning the installation, prepare the deck by making sure it is clean and free of any debris that could adversely affect the installation of the anchor sheet.
- Step Two: An ASTM D226 Type II anchor sheet should be laid loosely on the deck with a minimum of three-inch side laps and six-inch end laps. This sheet should be mechanically fastened per local building codes unless otherwise specified by Polyglass for the project conditions.
Fasteners should be corrosive resistant, 11 gauge ring-shank “Simplex” type nails with a minimum of one-inch diameter metal disc. These should be installed at a minimum rate of 12 inches.
- Step Three: Before installing the self-adhered Polystick TU Plus underlayment, cut it into suitable workable length sheets before placement.
- Step Four: Lay the material in place, starting at the lowest point. Overlap the seams at a three-inch minimum and end laps at a six-inch minimum.
- Step Five: Peel half of the backing off the roll and apply firm even pressure from the center to the outer edges. Then, remove the backing from the remaining half of the roll and apply pressure.
Polyglass requires a minimum of 40 pounds weighted roller. If safety is an issue on steep slopes, a stiff broom with approximately 40 pounds of load applied onto the field underlayment is acceptable.
Hand rollers are acceptable for rolling patches, laps, or small areas of the roof that are not accessible to a large roller or broom.
- Step Six: Polystick TU Plus self-adhered underlayment should be back-nailed at the selvage edge seam using the fasteners and spacing noted in Step Two. Install fastenings using the area marked “nail area” on the face of the underlayment.
- Step Seven: Apply a headlap underlayment layer of Polystick TU Plus to cover the back-nailed area.
- Step Eight: For any over-fabric and over-granule laps, apply a six-inch-wide uniform layer of PolyPlus® 50 premium modified wet/dry cement or Polyglass PG 500 modified cement applied in between the lap application.
Polystick® TU Plus
Polystick TU Plus is a rubberized waterproofing underlayment that features ADESO® Self-Adhered Dual-Compound Technology. It has high-strength polyester fabric on the upper surface and an aggressive self-adhesive compound on the bottom layer. It is ideal as a steep-sloped roof underlayment where tiles are stacked on the roof for long periods.
Polyplus® 50 Premium modified wet/dry cement
Polyplus 50 wet/dry cement is ideal for flashing details and attaching membranes to steep-sloped roofs thanks to its “trowel-grade” consistency. The modified, superior quality formulation is also useful in damp, wet, or even underwater conditions.
Polyglass PG 500 modified cement
PG 500 modified cement is suitable for attaching membranes and flashing details to steep-sloped roofs thanks to its heavy “trowel-grade” consistency. The elasticity of this high-quality formulation makes it superior to standard plastic cement.
For more information, contact your Polyglass technical services representative.