How to Install a Roof Flange for a Mast

The roof flange surrounds a mast to keep water from seeping in under the roof. A flange made to fit around a mast on a roof is needed to create a proper seal. These are available at home improvement stores. The flange should be installed before the mast for the most secure fit. Using this method leaves the doughnut-shaped flange intact, and the mast is inserted up into the roof through the flange.

Reciprocating saw
Roofing cement
Weather collar
Mast flange
Phillips screwdriver
Shingles
Roofing nails

Instructions

- 1
  Pull shingles off the roof in the area for installing the roof flange.
- 2
  Cut out a hole in the roof large enough for the mast to fit through with a reciprocating saw.
- 3
  Spread roofing cement on the bottom of the weather collar for the flange.
- 4
  Press the weather collar onto the roof so the hole in the collar lines up with the hole in the roof.
- 5
  Cover the bottom of the mast flange with roofing cement.
- 6
  Affix the mast flange to the roof on top of the weather collar, carefully lining up the holes in the flange, collar and roof.
- 7
  Screw the mast flange onto the roof with the screw included with the part.
- 8
  Push the mast up from the attic space through the hole in the roof, and use a Phillips screwdriver to tighten the screws on the flange's band clamps that hold the mast in place.
- 9
  Spread roofing cement on the back of shingles to replace the removed shingles.
- 10
  Lay the shingles on the roof from the bottom portion of the area, toward the ridge. Overlap the new shingles so they match the overlap on the existing shingles. Cover half of the flange material with shingles as you install them.
- 11
  Nail roofing nails into the shingles to match the number and arrangement of nails in the existing roof shingles.

How to Install Radiant Guard in a Heavy Truss Attic

How to Troubleshoot Shed Dormer Roof Problems

Roof Repairs