How to Flash Around a Curb With Roll Roofing

The installation of a skylight usually requires the placement of a curbed frame around the hole cut through your roof to accommodate the skylight. Though this curb is small, it’s still a point at which water can seep through the roof and into the interior of your home. To prevent this, builders place flashing around the curb and over the joints between the roof and the skylight to direct water over and around the skylight rather than allow it through the gaps between. To serve as a secondary protection from water seepage, roll roofing material is flashed around the curb, flush with the roof surface to prevent water from seeping through the flashing edges.

Phillips-head screwdriver
Roll roofing
Utility knife
Roofing nails
Hammer
Asphalt roofing cement
Trowel

Instructions

- 1
  Remove the skylight from the curbing if it’s already installed, by removing the screws holding the metal flashing in place and then unscrewing the skylight while holding it in place. Lift the skylight from the frame and set it out of the way.
- 2
  Cut a piece of roll roofing that’s as long as the width of the roll plus the height of the curb and an additional 3 inches for overlapping any strip of roofing running beneath the skylight frame. Use a utility knife to make the cut.
- 3
  Place the cut piece of roofing centered beneath the skylight frame with the top of the roofing piece running up the edge of the curb of the frame to lie flush with the curb top, and the bottom of the roofing piece overlapping the strip of roofing material running beneath frame. Place two cuts along the side of the material at the top to either side of the curb running at 45 degree angles from the base of the curb to the top of the strip of the roofing piece. Fold the two angled pieces of the cut roofing against the side of the curb while laying the other side of the cut piece flat against the roof. You should end up with a tabbed piece of roofing folding against the bottom of the curb with angled tabs placed along the sides.
- 4
  Run rolls of roofing material over the roof and to the curbside. Cut the material so that it folds up the side of the curb, repeating the tabbing process for any pieces that must run around the top and bottom of the curb frame. Repeat the same roofing piece process for the top of the curb frame that you used to place the roofing against the bottom. After finishing, you should have smoothly folded roll roofing on all sides of the curb, ending flush with the curb top.
- 5
  Replace the skylight and screw it securely to the frame. Replace the metal flashing back over the skylight beginning with the bottom flashing, and then placing the sided followed by the top piece. Nail the flashing in place with roofing nails.
- 6
  Cover the roll roofing with asphalt roofing cement to seal the seams of the pieces. Use a trowel to spread the cement in place.

How to Calculate Average Butterfly Roof Angles

How to Install a Rake Mold on a Metal Roof

Exterior Remodeling