How to Vent a Shed-style Roof
Avoid putting holes in the roof when you don't need to. When the peak of a shed-style roof is at least 18 inches higher than the top of the building's walls you can install vents in the end walls just below the peak. This area is like half of a gable end. If the roof has been installed correctly, this is a non-load bearing location where there is minimal framing to get in the way of a right-triangle vent of your choice. For best results, plan to install one vent on each half-gable end. Install these vents once the sheathing is in place and before the siding is installed.
Determine the pitch of the roof by: using the level to mark a plumb line on the face of a gable-end fascia; placing the pivot point (spot at the base of the right triangle) of a speed square at the bottom of the plumb line with the backside of the right triangle on the plumb line; and reading the pitch where the bottom of the fascia passes through the slot at the bottom of the speed square (common rafter scale).
Buy two, right-triangle vents with the same pitch as your roof. Get the correct orientation since one needs to face right while the other faces left.
Measure the three sides of one vent, minus the flange or frame, and draw an outline of it on each gable end. Lay this out so the angled side of the vent follows the angled underside of the roof line. Keep the angled line just below the top framing member of the half-gable.
Cut out the sheathing inside the lines you drew in step three, using the saw. Set the saw cut depth to match the thickness of the sheathing so you don't cut through any framing. If there are no framing components in the way, or the thickness of the vent will allow you to set the vent in the opening and nail it in place through the flange, then go on to step six.
Remove existing framing that will not allow the vent to fit all the way into the opening. Add new framing around the inside of the opening creating a box for the vent to fit into by cutting the two-by-four lumber into lengths that fit between the remaining framing components and fastening them in place with the two-inch deck screws.
Apply a bead of silicone caulk all around the back of the flange of each right-triangle vent. Place the vents into the holes and fasten in place by driving nails or screws through the flanges and into the sheathing.
Fit the siding to the edges of each vent frame or over the top, depending on your vent type.
Things You Will Need
- Speed square
- Tape measure
- Circular saw
- 2-by-4 lumber (optional)
- Screw gun (optional)
- 2-inch deck screws (optional)
- Roofing nails
- Right-triangle vents vary in their frame sizes, depths and finish details. Follow the manufacturer's instructions on cutting the holes for the vents you buy.
- When the building is already sided, consider using a vent that is made for that purpose. These vents may also have separate molding pieces to finish them attractively. You will also need to add framing to the inside of the gable end.
- Wear eye protection when hammering and cutting.
- Follow ladder safety guidelines.