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!

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Decided to take the good advice I’ve been given here and replace my flat roof.

Got a first estimate from an experienced licensed roofing company who believes major problem stems from aluminum ridge-cap on peak of the roof where the flat roof that will be replaced is married to the shingled roof. He plans to add a new layer of GAF Ruberoid Torch Smooth Membrane over the old rolled roof. The aluminum ridge cap would be replaced by membrane plus two vents in the flat roof which he figured to be almost double the vent capacity I need for this ~ 16x40 flat roof.

The gutter that runs the length of the flat roof has 30 y.o. aluminum Gutter Helmet installed - directly nailed into the flat roof. The manufacturer told me they now recommend facia mount installation. I think the gutter helmets may have outlived their useful life because there is several places where they drip over onto the siding. Bottom of soffit has rotted in two sections. The roofer said he would repair these sections included in the price of his estimate. Also said he’d replace the entire soffit for an extra fee ($400) if I want. He said he didn’t think the soffit needed ventholes (which I thought odd) but that he would drill them and install the vent covers for them if I insisted.

I believe he said he would lift up the Gutter Helmets and lap the membrane into the gutter. Not sure how he would reset the Gutter Helmets or if I should keep them or get some kind of new gutter. Think he said he would or might provide some kind of double hulled gutter replacement. Don’t have that part in writing.

Does this all strike you experts as fair and reasonable?

Thank you!

No, tear it off to the deck. All the repairs say you’ve got damage you don’t want to cover up. I’ve spent a lot of time stomping and nailing down those aluminum ridge vents when we got fine blowing snow. You can ridge vent that attic from the pitched side…


Thank you. Tearing it down to the deck makes great sense.

Also, I think you’re saying it’s preferable to vent the steeply pitched side of the roof near the ridge peak but please correct me if I’m misreading.

Thanks again!

Make your ventilation cut on the steep side and keep the flat sealed. Cut down cobra or similar, cap the vent on the street side so it doesn’t look funky, and run whatever membrane to the ridge. Asking for trouble with it vented the way it is…

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I’m surprised you’re even considering leaving that roof on and any roofer that proposed a recover I would chase from my property with a tear off tool! You are seeing leaks in your house, can you imagine what else is wet on that deck that hasn’t made its way in yet?


That gutter helmet system will need to be completely removed and not returned.
You might need to remove and
re-attach/replace the gutter If there is rotting fascia wood behind it.
Especially since you say it is dipping in several areas.

Also, i would use granulated torch down
So you dont have to worry about keeping it painted.

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the opening on the side of the boot is obvious you can just cement and fabric it again or clean and prime the area and put a piece of sbs self adhering in and seal the edges also a bead of sealant around pipe to boot joint

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Did you see all the pictures?

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