How to Waterproof Around a Roof Vent

Lead Image
  • 2-4 hours
  • Intermediate
  • 25-70
What You'll Need
Silicone sealant
Caulking gun

A leaky roof vent can cause all sorts of problems in your home. From compromising the structural integrity to harboring mold growth, a roof vent that isn't properly waterproofed can ruin your roof. The following tips demonstrate how to waterproof a roof vent so that never happens.

Step 1—Inspect Your Roof

Before waterproofing your roof vent, make sure that the shingles surrounding your roof vent are in good repair. Inspect your roof from the direction of the prevailing winds in your area. Make a note of any dips or rises in the surface of your roof. Also, note any shingles that have been warped or buckled.

Step 2—Repair or Replace the Needed Shingles

Any areas on the roof that will allow water to run uphill and under shingles needs to be fixed before waterproofing your roof vent. Using a silicone sealant and caulking gun, seal any shingles that are of concern around the three open sides. Be sure to use enough sealant to make sufficient contact with the buckled and warped shingles so that there is no gap under them.

Step 3—Waterproof Your Roof Vent with Caulk

After replacing or repairing any shingles that needed it, waterproof your roof vent. You can do this by a few different methods. The most common is to use roof caulking.

Identify the edge where your vent or, in some cases, metal flashing, meets your roof. There is no need to remove existing sealant unless it is already peeling off, or there is an excessive amount of sealant already there. Make sure that you apply a generous amount of caulk to the joint where the vent meets your roof. Then, use your finger to smooth it out, making sure to cover any cracks or crevices.

Step 3.5—Waterproof Your Roof Vent with Flashing

Another method to waterproof around roof vents is using sheet metal. Wrap a thin piece of sheet metal around the vent and secure it with rivets. Once you have the metal installed, apply a generous amount of sealant around the edges of the metal, paying special attention to any cracks or gaps where it meets the roof.

Once you have applied the sealant, spread it out using either your finger or a small tool. Don't use too much, as it won't dry properly and could create more problems then it solves.

Step 4—Finish Up

Keep in mind that applying a sealant creates a barrier between water and your roof, and water will take the path of least resistance. That means that if there are any other areas of weakness on your roof, the water will travel there instead, so regularly inspecting your roof will prevent costly damage in the end.