How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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What is a roofing boot?
Sunday, July 1, 2018
A roof boot is also called a plumbing vent boot, pipe boot, or pipe flashing. It is a preformed flashing installed to waterproof pipe penetrations of a roof, like plumbing vent pipes and electrical service mast pipes. The most common type is made from lead, a flexible metal that makes it easy to adjust the base to the roof pitch and bend the top of the boot into the pipe end for a rainproof seal. A lead roof boot is shown below, before and after installation on a shingle roof.
The only problem with lead roof boots is that squirrels love to chew them up. Lead, although poisonous, tastes sweet and that may be the attraction. When the lead gets eaten away at the top of the pipe, you’ve got a roof leak; usually not enough to stain the ceiling below, but it will stain the surrounding sheathing and may cause an area of rot around it. Here’s a couple of pictures of typical damage, with the right one munched all the the down to the shingles. Below that are two ways that the lead boots can be protected. The homemade wire-mesh enclosure is easy, but a manufactured sleeve that slips over the boot looks better.
There are also boots made with a rubber sleeve that slides over the pipe and snugs to it, as shown below at left on a metal roof. We recommend using a pipe clamp at the top because the rubber eventually loosens and fails (as in the right photo) and the clamp will extend the life of the boot.
And there are “retro-fit” versions of this type of boot specifically made for electric service masts. They are designed with a closable seam to fit around roof pipe penetrations where it is not possible to slide the boot down from the top. We occasionally see a lead boot used for a service mast, like in the photo below, but it is not rated for that use, and will always leak within a few months after the caulk at the top fails.
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To learn more about roofs and attics, see these other blog posts:
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