Which roof flashing is best? When exhausting a radon mitigation system through a roof, it is important to use quality materials. For example, if a roof flashing fails, a homeowner could end up with a leak. So let’s look at a few flashing options and which one we recommend for radon mitigation. Click here to check out the video.
In the past, we’ve used plastic and galvanized flashings. Plastic is inexpensive and easy to use, but it can degrade and is prone to cracking at installation and in the cold, which is not ideal in Minnesota.
Galvanized flashings are sturdier and come in a variety of colors but are prone to rust.
We have turned to aluminum flashings because they are sturdy and rust-resistant.
The flashings are meant for a 3 or 4-inch pipe. We use a 4-inch pipe to exhaust because the wider pipe is less likely to freeze in the winter. To modify the flashing, we use a snips to cut in to the 4-inch line and carefully pull the 3-inch ring out. We do not recommend using a knife to adjust the size because it can easily slice too far into the flashing.
The weak point is the rubber seal from the flashing to the pipe, so we also use rain collars to prolong the life of the flashing. The rain collar protects the rubber ring that will degrade over time from the sun.
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