Fix leak in torch down roof | old air vent rubber boot patch job failed after 10+/- yrs

Trying to fix a repair I made on a torch down roof about 10 years ago. The roof itself is about 35 years old I guess.

The leak seems to come from the 2 inch air vent stack that I previously repaired with a rubber boot, roof cement and mesh.

First thing I noticed when I went to check on it today was the crack on the right side of the stack and the bubble on the left side. I aimed a garden hose at these for a while but could not replicate the leak I had in a recent rain storm with flat line winds from west to east and heavy rain over a long period of time.

After about 10 minutes of testing various features on the roof I tied off the garden hose aiming it from west to east ( I will post an additional picture) and the leak was evident in the house as soon as I came down from the roof. It stopped about three minutes after I shut the hose off. So, this narrows it down.

My question is what is the best way to repair this old patchwork.

Many thanks!!!

This test replicated the leak I had in recent storm …

Note that in this picture I crushed down the large bubble (~1.5” diameter) to the right of the pipe’s shadow that is more visible in the first picture. The air out pretty easily. Maybe that’s the trouble spot but I’m just guessing.

What type of roof cement did you use to flash the pipe boot?

Plastic cement is not compatible with modified you are supposed to use neoprene on modified.

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If something is growing out of your roof, it is a leak for sure.
Past time to replace that roof…

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Thank you for your advice.

It was oil-based for sure. No good, huh? So cut out all I can and try a neoprene roof adhesive to hold down the boot?

Someone mentioned silver coat. Is that something I should spread around too when conditions allow?

Many thanks again!

Thank you kindly for your response

Do you mean the air bubble under the boot? Axiom said I likely used the wrong cement (Should’ve use neoprene) so maybe that grew from a chemical reaction between the oil basement and the rubber boot?!?

Or, if you’re referring to the moss, it’s because the house has been under two giant poplar trees (just cut them down a few months ago) for a good portion of the last hundred years catch up. Beautiful trees but always dropping something nasty in every season of the year. Anyway, had a fair amount of moss growing underneath the drip line of the trees. It’s pretty superficial though. Scrapes off with some elbow grease.

Yes, the plant material growing out of the seam.
It is a leak.
All those old exposed nails are a leak also.
I also think that straight line that you have already mentioned where the cement has opened up next to the flashing is a leak too.

Roof needs replacing…

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These leaks get crazy. I would get a gallon of GACO liquid tape. Roof has to be dry. I would start at the vent and work outward. Hit the seam In that area. A gallon isnt going to go very far. About 5x5.
The roof is toast so whatever you do is better than a leak. You could prime the area, put a 4" star vent on the plumbing pipe. Set it in Gardner leak stopper from Lowes. It’s compatible with GTA.
Other choice is a cold process APP, with a new vent. Prime. I wouldn’t use a base sheet. Cold process modified adhesive. It aint gonna like the GTA, so seal the lead edge with a heavy mod-bit caulk.

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I believe silver coat is only to help protect against UV breakdown and also helps a bit with cooling to reflect sun heat. I don’t believe silver coat has any sealing properties, other than it helps to prevent cracking that comes from UV.


Really appreciate all the good advice here. I literally Jersey-rigged a diverter (out of N.J. license plates I’ve collected over the years) and inverted a large funnel over the 2” pvc pipe to hold me til I can get to Lowe’s and make a better temporary solution that can hold me through the winter and ultimately a new roof and soffit . Many, many thanks to all!!!

Don’t put aluminum coating on it. It’ll divorce any repairs. Use wintergrade MB flashing cement and work in it. AND… you need a new roof!