Installing a Ridge Vent

Ridge vents adjust to different roof pitches and come in painted metal typically aluminum and plastic versions. Although metal vents have been around longer, homeowners and contractors now prefer plastic vents like the Builder's Edge series sold here at CornerHardware.com. Unlike their metal counterparts, plastic ridge vents don't dent, and they can be capped with shingles to blend with the rest of the roof. (Most metal vents can't be capped.)

To estimate how many feet of vent you'll need, just measure the length of the roof peak, or ridge, minus any sections interrupted by chimneys or sidewalls. The simple instructions that follow apply to any gable-style roof that's covered with asphalt or wood shingles.

Step by Step
1. Remove the old cap shingles. These are the shingles that cover the roof peak, and they're installed with roofing nails and/or roof cement. Remove them with a claw hammer and a flat bar. You won't be able to reuse the shingles, but it's less messy if you remove them intact instead of in small pieces.

2. Mark lines for the ridge opening. First, check the manufacturer's instructions that came with your ridge vent to find out how wide the roof opening should be. Using your tape measure, mark the distance from the roof peak to the bottom of the opening. You'll need to do this on both sides of the peak, and on both ends of the area the vent will cover. (You may want to check out our tips and tricks on accurate measuring and marking.)

Next, run a chalk line between your marks on one side of the roof peak, and snap it to mark your cut line. Repeat on the other side of the peak. (For the Builder's Edge vents, snap your cutout lines 1 1/4 inches below either side of the peak. This cutout should leave a 1/2-inch-wide opening on either side of the ridge board, the topmost board of the roof.) Be sure to make your cutout no wider than the manufacturer's recommendations.

3. Cut the ridge opening. Use a circular saw fitted with a remodeling blade designed to cut through wood that may contain nails. (For details about remodeling blades, see our Buyer's Guide to Circular Saw Blades.) Before you cut, don a dust mask and protective goggles you may see some sparks fly as you're cutting.

You can also expect the blade to get gummed up, especially in the case of asphalt shingles. If the shingle residue starts to impede your progress, unplug the saw and clean the blade with a rag dipped in mineral spirits. Pros and experienced DIYers using powerful saws adjust the blade depth to cut through the shingles and sheathing all at once, just skimming the rafter tops. If your roof has thick sheathing and multiple layers of shingles, make a first cut through the shingles only and a second cut through the sheathing.

Follow the lines you marked, but stop the cuts 12 inches from each gable end, chimney or intersecting hip roof. Your circular saw won't be able to cut all the way up to vertical obstructions, and you want to avoid cutting into any of the crucial framing at the ends of your roof. As you're sawing, be careful to not cut into the rafter tops. Finally, use a sharp chisel to chop through the last 12 inches of sheathing at the end of each cut. This will leave you with a pair of long, narrow openings on either side of the ridge board.

4. Nail the ridge vent in place. Vent sections are designed to interlock and can also be cut to length. Use a crosscut saw or a circular saw to cut plastic vents and tin snips to cut metal vents. Though most vents fit a wide range of roof pitches, you'll find that flexing a plastic vent back and forth a few times will make it adjust more easily to your roof.

Fasten each vent section over the peak, using the nails recommended by the manufacturer. When cutting and joining sections, keep the layered baffle material intact inside the vent; it keeps out insects and driving rain and snow. For the best appearance, run your vent all the way to the end of the ridge. Where the ridge is interrupted by a chimney or other obstruction, butt the vent up against the vertical surface and seal the intersection with roofing cement or polyurethane sealant. Cover the joint with flashing.

5. Install cap shingles. You can buy cap shingles as precut squares or make your own by cutting square sections from standard shingles. Begin at the end of the roof that faces away from prevailing winds. Start off with a double cap layer bedded in roof cement. Overlap each succeeding cap by half (with asphalt shingles, expose only rough-particle-covered part of the shingle). Now that your roof can breathe easier, so can you.

Hire a Pro
If you're short on time or uncomfortable taking on this kind of job, check out our Services channel. We'll help you find a trustworthy, prescreened professional contractor in your area.

Tim Snyder, writer, photographer and carpenter, was a senior editor at Fine Homebuilding magazine and executive editor of American Woodworker magazine. With TV personality Norm Abram, Snyder coauthored two books in the best-selling New Yankee Workshop series. He's also written books on deck design and furniture making.