Vent Pipe Collars

One of the most common roof leaks I find is also one of the simplest: a deteriorated vent pipe collar.

Plumbing vent pipes extend through your roof, and a pipe collar is installed around each penetration to keep water out. Many common pipe collars use a rubber or vinyl seal that fits tightly around the pipe.

The problem is that the roof may last much longer than that rubber seal.

Years of exposure to sunlight, heat, cold and changing temperatures can cause the seal to dry out, crack and eventually separate from the pipe. Once that happens, rainwater can run down the pipe and into the roof decking or attic.

From the ground, the roof may look perfectly fine.

Even from inside the house, the first indication might be a small ceiling stain or occasional leak during heavy rain. Meanwhile, water may have already been getting into the roof decking around the pipe.

This is another reason I prefer getting on the roof and inspecting penetrations up close whenever conditions safely allow.

Usually, no.

If the shingles and roof around the vent pipe are still in good condition, a failed pipe collar can often be repaired without replacing the entire roof.

I look at the condition of the collar, surrounding shingles, flashing and roof decking to determine how far the problem has progressed.

If water has damaged the decking underneath, the repair may require removing shingles around the vent, replacing the damaged wood and properly installing a new pipe collar.

The important thing is to fix the source of the leak, not simply cover the deteriorated rubber with another layer of caulk.

Caulk certainly has its place in roofing, but it shouldn't be used as a substitute for properly repairing a failed roof component.

I've inspected plenty of pipe collars that have been covered with layers of roofing cement or sealant in an attempt to stop a leak.

Sometimes that buys some time. It doesn't necessarily correct the underlying problem.

If the collar has failed, I would rather make a proper repair than create something the next roofer has to excavate with a shovel. 

Around plumbing vent pipes, I'm looking for cracked or deteriorated rubber, gaps around the pipe, exposed fasteners, damaged shingles, previous repairs and signs that water may be getting underneath the roofing system.

I also pay attention to the condition of the roof itself.

A failed pipe collar on an otherwise healthy roof is very different from a failed pipe collar on a roof where the shingles are already brittle, worn and heavily deteriorated.

A leaking pipe collar is a perfect example of why a roof leak doesn't automatically mean you need a new roof.

Sometimes a relatively small component has simply reached the end of its life before the rest of the roofing system.

If the roof is still worth repairing, fix the problem properly and keep the roof doing its job.

If I find larger issues while I'm inspecting it, I'll show you what I found and explain your options.

Repair when you can. Replace when you should.

— Keith Nagy
Owner/operator Nagy Roof and Repair