One of my pet peeves as a Seattle home inspector is the use of inadequate flashings for pipes that penetrate the roofing materials. My opinion is that the flashings chosen should be designed to last as long as the roof is projected to last–if possible. There are some types of roofs–like slate or steel where this may be difficult–but let’s at least do the best we can.
On a recent wood shake roof, that was about 25-30 years old–and at the end of its life–we can see a good example of a flashing that should never have been used with this roof. The rubber component of this flashing is good for about 15-20 years–maybe less in environments harsher than the cloudy NW. They certainly don’t last 25-30 years. This one has been leaking for quite some time.
Why does this happen? Cost. A good flashing, that will last all of the 25-30 years of this roof, might cost $25.00 per pipe as opposed to $3.75. You might want to consider copper starting at $75.00 per pipe. A roof with 4-5 pipes sticking through it starts to add up to a lot of lattes–so most home owners go with the flashings that cost as much as a latte.
I have seen these latte-priced flashings on metal roofs and heavy asphalt shingle roofs designed to last much longer than the rubber flashing. These flashings might need to be replaced two or three times over the life of the roof and when these costs are factored in (labor and materials, one might have been better off choosing the more expensive flashings from the get-go–ones that might even be able to be reused when the roof is relaced. Here are a couple of pictures of such flashings. The first picture is a rubber/metal pipe flashing on a faux-slate roof that is designed to last 50 years or more.
This next picture is of a rubber pipe flashing on a typical 25 to 35 year asphalt roof that has already failed after 15 years.
Lead type flashings work very well in some areas of the country, but sometimes squirrels like to chew on the lead–perhaps that is why they are known to be squirrelly.
By Charles Buell, Real Estate Inspections in Seattle
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