Making Vents in Soffits in the Attic

Examine the soffits from inside the attic. Clear any obstructions. Measure the distance between rafters, or any other obstructions like soffit joists, for instance. Record the measurements.

Stand outside underneath the soffit. Erect a ladder, if necessary, to access the soffits. Follow the ladder safety tips enumerated in "Top Tips for Ladder and Stepladder Safety" in the Resources section of this article.

Position the first soffit vent on one end of the soffit, at least 3 inches from the edge. Choose a spot that will not overlay any of the roof's rafters, to optimize airflow. Hold the soffit vent against the soffit. Center it between the edges of the soffit. Measure the distance between the edge of the soffit vent and the edge of the soffit at several points. Consistent distances ensure that the soffit vent is straight and centered.

Trace the outline of the soffit vent onto the soffit, with a grease pencil.

Measure the distance from the outer edge of the soffit to the edge of the vent slats on all four sides of the soffit vent. Use these measurements to outline the perimeter of the soffit vent's slats on the soffit inside the outline of the soffit vent you made in Step 4.

Line a chalk line up with the back edge of the soffit vent slat outline you made in Step 5. Run the chalk line down the length of the soffit. Make sure that it is straight. Snap the chalk line. Repeat with the front edge of the soffit vent slat outline. The end result will be two parallel lines running the length of the soffit.

Drill a hole in the center of the first soffit vent outline. Thread a measuring tape through the hole to measure the thickness of the soffit. Insert a bent hanger into the hole to ferret out the location of the first rafter. Mark the approximate locations of the rafters outside the soffit, using the measurements you took in Step 1.

Mark the position of the other soffit vents. Space the soffit vents at the desired distances. Do not place any soffit vents directly over the rafters. The chalk lines you made in Step 6 represent the long edges of the soffit vent holes you will cut. Measure the length of the soffit vent cover. Make two perpendicular lines between the parallel lines to designate the location of each soffit vent. Use a carpenter's square to make sure the lines are perfectly straight and perpendicular. Mark an "x" in the middle of each soffit vent hole to differentiate vent holes and the space between neighboring vent holes.

Cut out the soffit vent holes. Use a power saw to make the lengthwise cuts. Adjust the blade of the power saw to cut roughly 1/8-inch deeper than the thickness of the soffit, measured in Step 7. Use a jigsaw to cut the short ends of the soffit vent.

Place each soffit vent over its respective vent hole. Center the vent's slats over the hole. Drill the screws provided into the screw holes in the vent.