How to Install a Duct to a Roof

Climb into the attic space and hold up the duct to determine where it will exit the attic roof. The exit must be between two wooden rafter beams. Hammer the long nail between the two rafters and into the roof.

Exit the home and climb onto the roof via the ladder. Walk to the location where the nail shaft extends for the roof and hammer it back down into the home.

Set a roof vent cap temporarily on top of the area and trace around the perimeter with a piece of chalk.

Cut around the chalk line, using the utility knife. Keep the knife 1/2 inch inside the chalk at all times. If the roofing material consists of tiles or slate, detach them with a prybar to remove the nails holding them to the underlying plywood.

Don safety glasses and insert a 1/2-inch bit into the drill. Drill a hole in the exposed plywood until you feel the bit slide, which means you have penetrated the interior.

Set the drill aside and insert a jigsaw into the hole. Squeeze the trigger on the saw to cut around the perimeter of the opening to create the roof hole.

Lift up the shingles along the sides of the hole and slide the vent under them until it aligns over the hole. Insert galvanized roofing nails into the holes around the perimeter of the vent to secure it to the roof. If you have slate or tile, install the vent fully, then reinstall the materials around it.

Insert a tube of roofing cement into a caulking gun and apply a 1/4-inch bead around the entire top lip of the vent. Press the shingles down to hold them in place over the vent so they deflect rainwater.

Go back inside the home and raise the duct up to the bottom of the installed vent. Push it over the round lip on the bottom of the vent and wrap foil duct tape around the edge to hold it in place.