The final step to installing a roof exhausted bathroom fan is the installation of the roof vent. Purchase a roof vent with flashing connecting to the vent. The important part of installing a roof vent for a bathroom fan is eliminating the possibilities of roof leaks. The upper portion of the roof vent will fit under the roof shingles to accomplish this.
Locate the point where the bathroom fan exhaust will exit the roof. The exhaust will install through the roof between two rafters. Once you have determined where the exhaust pipe will go through the roof, drive a large nail through the roof at the centre of the pipe circumference.
Climb a ladder to the roof, and locate the nail that you just drove through the roof. Use a tape measure to determine that roof vent will be 2 feet away from any obstructions. Set the tape measure to 2 feet, and rotate around the nail.
Mark the hole for the exhaust pipe and roof vent with chalk. There are two ways to accomplish marking the roof. Take the piece of exhaust pipe, centre the pipe over the nail and trace the pipe with the chalk. You can also measure half the circumference of the pipe in four directions from the nail, and draw a rough circle with the chalk.
Cut the hole out of the roof at the chalk outline with a reciprocating saw. Cut through the shingles and the sheathing of the roof. If the piece of roof does not fall into the attic, pull the cut piece out of the roof and throw the piece of wood away.
Set the roof vent with attached flashing into the hole. Place chalk marks on the top two levels of shingles the flashing is over the top of. Pull the roof vent out of the hole. Use a flat pry bar to remove the nails from the shingles you just marked. The nails are located at the notched slits in the shingles.
Set the roof vent back into the hole in the roof. Outline the top half of the flashing with the chalk. Remove the roof vent, and measure ½ inch inside of the trace outline. Cut the shingles with a utility knife at the new measurements. This will allow the top portion of the roof vent flashing to sit under the shingles which will prevent any leaks.
Set the roof vent into the hole, and position the shingles over the top portion of the roof vent flashing. Drive roofing nails around the outside edge of the roof flashing. Use silicone caulk and a caulking gun to apply a small amount of caulk over any exposed nail heads.
Go back inside the attic, and connect the exhaust pipe to the bathroom exhaust fan and the roof vent using clamps. Secure the clamps with a Phillips-head screwdriver.
If you are uncomfortable working on the roof, hire a professional.