Install a Flat Roof Vent in 5 Steps

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  • 4-6 hours
  • Intermediate
  • 75-400
What You'll Need
Reciprocating saw
Replacement shingles
Roofing tar
Tar supplies

A flat roof can sometimes be a challenge to bring adequate ventilation to. Flat roofing requires a different type of vent then standard angled roofs. Just like any roof, it is required that you have flat roof ventilation in order to allow fumes, gases, and airflow to correctly exit your home or other space. Even if you have a small shed you should allow for a proper vent to keep the air fresher in the space. Installing the vent on a flat roof is no different than installing one on an angled roof. The difference is the vent itself. You need to find a vent that is compatible with a flat roof. For this article, the instructions will be on how to install a mushroom vent. A mushroom vent is different from a turbine vent. It is shaped like a post with a cap on the top. The cap is larger than the post and raised away from it allowing air to escape but no water to get in. There are very basic mushroom vents as well as more decorative mushroom vents that can be used for your project.

Step 1: Determine the Center Point

When you are running your ventilation pipe through the attic drill a hole in the roof from the attic out. Leave the screw in so that you can see it when you go on the roof to cut the hole out. Do not cut through any rafters when installing your vent, it is not worth weakening the structure to get the vent a couple of inches to one side or the other.

Step 2: Remove the Tiles

Once you determine where the vent will go, remove the tiles in the surrounding area, try to conserve what you can and minimize damage to surrounding tiles.

Step 3: Cut the Hole

You will need to cut your hole for the vent with a small amount of leeway for expansion when needed. It is easiest to cut from the center of the hole out to the edge of the circle and then around the circumference of where the vent will go.

Step 4: Install Vent with Flashing

Install the vent into the venting hole and surround it with the correct flashing. Some vents do not require flashing, use the manufacturer’s suggestions to decide if you need it or not. You will need to use nails to hold the flashing in place and the roofing tar to ensure that you do not have any spaces that will let moisture into the attic space.

Step 5: Replace

Once the vent is installed with the flashing and completely sealed with roofing tar you will need to replace the roofing tiles. Many flat roofs do not have roofing tiles and you will just need to replace the rocks or gravel that you moved aside to gain access to the roof.

Whether you are installing a roof vent to ventilate a bathroom, laundry room or gas fireplace these basic instructions will allow you to install one with minimal effort. It is always recommended that you check with local building authorities to get any guidance, as well as building codes, for roof ventilation in your area.