How to Add Roof Vents

Crawl inside the attic. Hold the end of a tape measure at the highest point of the roof – where the roof trusses meet--and place a soapstone mark 18-inches down from the roof peak. Pull the tape measure across the space between two roof trusses, aligned with the 18-inch mark. Place a second soapstone mark in the center of the two joists.

Align the nail with the mark located between the trusses. Drive the nail through the roof with a sharp blow from a hammer. Leave the attic.

Set up an extension ladder against a side of the house that does not have a gutter running along its eave. Walk the roof carefully until you locate the nail.

Measure the width of the roof vent opening. Add 1/2 inch to the measurement. Divide the number by two to determine the width from center. Hold the tape measure against the nail. Slide the tape measure until the width on center measurement displays on the tape. Place a soapstone mark on the roof. Repeat the procedure until all four sides of the opening are marked.

Cut along the soapstone lines until the roofing material is cut on all four sides of the nail. Slide a pry bar under the cut section of roofing. Pry up to loosen and remove the roofing from the area. Drill 1/2-inch holes with a drill motor equipped with a 1/8-inch drill bit. Slide the blade of a jigsaw into the drilled slot. Cut along the removed section of roofing until the wood sheathing separates from the roof.

Slide the pry bar under the material surrounding the cut hole. Lift the roofing gently. Pull out any nails found within two inches of the hole edges.

Slide the top flange of the roof vent under the second row of shingles below the top of the hole. Secure the vent by running one 8d nail through each corner and one between each corner nail. Leave the heads of all nails 1/2 inch above the surface of the roof sheathing.

Open a tube of roof cement. Place the roof cement inside a caulk gun. Apply a dab of cement under each nail head. Drive the heads of the nails tight to the sheathing. Apply a bead of cement underneath all loosened roof material. Press the material firmly toward the sheathing to seal the area.