How to Install Bath Vents Through a Roof

An important element in a bathroom is the exhaust fan.

Roof vents must be properly sealed.Roof vents must be properly sealed.
This fan removes air that is heavy in moisture and odors from the bathroom. The air from the bathroom must be vented outside your home, or else it can cause mold and mildew in other areas of the home. You can vent the air to an exterior wall away from a soffit vent that can draw it back into the attic, or you can vent it through the roof.

Dry-fit the duct work assembly that will run from the top of the bathroom fan to the roof and hold it in position on top of the fan. Draw a circle around the perimeter of the duct work onto the roof sheathing then lower the duct work.

Place a nail against the sheathing in the center of the circle and drive it through the roof to mark the location of the vent on the roof.

Use a ladder to climb up onto the roof and locate the nail. Look for an area where the shingles are lifted up off the roof.

Measure the width of the tube on the bottom of the vent hood and draw a circle slightly wider than that onto the roof with the nail in the center.

Drill a hole with a 1/2-inch drill bit along the line to provide a starting point for the reciprocating saw.

Saw through the roof with the reciprocating saw, starting at the 1/2-inch pilot hole and following the circle.

Place the vent hood into position on the roof and trace the outline of the flashing so you know the areas where you need to lift the shingles to get the flashing underneath. The flashing is the flat area around the vent hood.

Lift the shingles on the sides and top of the hole where the flashing will go with a pry bar. Remove the nails that hold those shingles in place by carefully sliding the pry bar between the shingles and the roof sheathing then lifting the shingles up.

Place the vent hood into position on the roof. Slide the top edge of the flashing underneath the shingles on the top and sides of the roof so the shingles overlap the edge of the flashing. This helps prevent water from seeping through underneath the flashing.

Drive galvanized nails, through the edge of the flashing every 4 inches, to secure it to the roof.

Apply a thick bead of silicone caulk around the edges of the flashing, as well as a drop on top of each nail. Lay the shingles on the top and sides of the vent hood, flush against the roof.

Things You Will Need

  • Duct work
  • Ladder
  • Hammer
  • Nail
  • Tape measure
  • Vent hood
  • Drill
  • 1/2-inch drill bit
  • Reciprocating saw
  • Safety goggles
  • Pry bar
  • Galvanized nails
  • Silicone caulk


  • When venting through the roof, you need to place the vent between two rafters, so you may need to install a 90-degree elbow in the duct work if there's a rafter directly over the fan.


  • Wear safety goggles when using the reciprocating saw.

About the Author

Carson Barrett began writing professionally in 2009. He has been published on various websites. Barrett is currently attending Bucks County Community College, pursuing a Bachelor of Arts in sports management.