How to Connect Vent Ducts to a Roof

Select the area of the roof where the vent duct will be installed. Choose a location as high on the roof as possible, but at least 8 inches below the ridge line. Select an area between two rafters.

Drive a long nail through the ceiling to mark the spot for vent installation.

Use the nail as a center point, and draw a circle with a diameter matching that of the desired vent aperture.

Find the protruding nail on the roof surface, and remove the shingles on the top and sides of the area to be covered by the vent, in a square surrounding the nail. Remove enough of the shingles to expose an area equal to that covered by the vent flange.

Drill a pilot hole at all four corners of the exposed square. Cut out the area between the holes with a reciprocating saw.

Apply an even bead of roofing cement to the underside of the vent flange, and slide it under the shingles surmounting the cutout. Ensure the vent is properly centered over the hole. The top flange should slide under the shingles, with the bottom remaining exposed.

Hammer galvanized roofing nails into the sides, bottom and top of the vent. Apply roofing cement to the nails and all exposed seams between the venting duct and the roof, with the exception of the bottom.