How to Install Roll Roofing for Your Low-Pitch Roof

Grab your measuring tape and measure the length and width of your roof’s surface. Multiply each length and width, and add each section to get the total surface area (in square footage). This number will tell you how many rolls you need for your project. You should buy 5% to 10% more material than your roof’s measured area to account for roll overhang, trimming, and covering up your roof’s valleys. Getting to know common roof rafter sizes can also help you confirm your measurements.

Begin by grabbing a push broom and remove all of the debris. As you clean, keep an eye out for loose nails and hammer them down. Afterward, take the time to clean out your gutters or hire a professional to deep clean them before you begin. Lastly, repair any loose or damaged wood or hire a local roofer for any areas in question.

Prepare your materials and lay the roofing rolls out flat by placing bricks on the corners to keep it in place. Secure roofing felt or primer over your bare sheathing to protect against leaks and provide insulation (while underlayment isn’t necessary, we highly recommend it). Next, add a layer of roofing cement to the edges of your roof and attach drip-edge metal flashing. Nail in the flashing to ensure water stays out of your roofing materials. Add a UV-resistant coating to exposed flashing cement.

Pro tip: If the temperature is under 50℉, lay out the roll in a garage to prevent breaking and stiffening.

Roll roofing is typically installed horizontally. So, you’ll want to grab your measuring tape or yardstick and measure 35 inches—the default roofing measurement—up from the bottom edge of the roof. This measurement will identify where your first roll layer goes, so you’ll need to mark a chalk line across the entire roof (ensure it’s straight so you lay your rolls uniformly).

Grab your gloves and a trowel and spread roofing cement along the edges of the roof—make sure it’s 1/8 to 1/4 inch thick. Apply the cement in horizontal sections, always staying below your chalk lines. Finish one area before moving on to the next one. If you don’t want to deal with cement, you can also use a self-adhesive modified bitumen—just keep in mind, it’s very sticky.

Take your utility knife, apply pressure, and cut your roll roofing to fit each section of your roof. Ensure each section is at least 35 inches wide and meets the chalk line when you lay it down.

Line up the edges of your roof roll and slowly lay the first layer down, pushing it into the wet cement to secure and stretch out any wrinkles. Gather your galvanized roofing nails and a hammer. Plant your feet on the roll and hammer your nails 6 to 10 inches apart across the roof length, ensuring that they are at least 1 inch away from the edges. As you hammer in each nail, avoid lifting your feet. Instead, push them back down as you nail the roof length—this helps stretch the roll. Seal plumbing vents by cutting a hole in the roll and slipping it over the vent. Finally, spread with cement and add boot flashing to keep the roll secure.

Make a new chalk line 32 in. up from the bottom and across your roof above the first 35-inch layer so you can overlap the layers (this way, rain can’t seep through any cracks). Next, grab your trowel and spread another layer of roofing cement across the roof and below the chalk line. Cut your roll, and apply the second layer the same way as the first, making sure the first 6 inches of the second layer overlaps the first layer.

Hammer in your nails (keep the first and second layers together) and spread the roll as you go. Overlay the valleys (where two slopes meet) with an 18-inch cut of roll and add roofing cement before laying the piece down. Seal the top layer edges with cement when all roll roofing is down. Apply roofing sealant over all the nail heads to protect them from the elements.

Walk the entire roof and seal all nails with cement (this will keep them from coming loose).

Take your razor knife and trim any excess roll roofing along your roof’s edges. Seal the edges with another layer of cement.

Once the cement has dried (check your manufacturer's can for drying instructions), you can move on to the final step of your project—cleaning your roof.

To do this, take your push broom and thoroughly clean any dirt, debris, loose nails, and mud off your roof. When you’re back on the ground, take a hose and spray down the roof—never use a hose while you’re on the roof, as it poses a slipping hazard.

When your roof is clean, you can pat yourself on the back for a job well done!