Roof Flashing Repairs - Need Sealant?

[The Critic]

During my biennial roof inspection, the following issue was brought to my attention:

There are four of these on the roof. On all four, it appears that someone, at some point, used a copious amount of sealant to seal the rubber donut to the pipe. Of the 4 people who looked at it, the opinions were split: 2 said it was fine, the other 2 thought the rubber boot had failed and the sealant is also starting to fail - so they suggested a "proper repair."

After much deliberation, I hired a roofing contractor to replace all 4 flashings and install new donuts. This is the outcome:

However, the roofer did not use any sealant during the repair - they just removed the tiles, installed new flashing and slipped a rubber donut down the pipe. I assume the rubber donut is suppose to seal the gap and divert water away from the flashing. Would adding some sealant/mastic to this area improve sealing?

 

[Gokhan]

You absolutely, 100% need sealant. Bring the roofer back.



I brought the roofer back like five times until they sealed the base of the A/C intake duct to my satisfaction, to the point that I could no longer see light coming when looking inside the intake.

 

[PontiacHO]

Looks like you have a slate roof. Mine is a shingle roof. I used a “boot” that slides over the existing vent/seal assembly. No need to remove the old vent/seal. The kit came with a sealant to ensure the boot adhered. Saying that and not sure such a kit-boot will work on slate but worth looking into.

Reread your post. Since he couldn’t slip the boot base under the upper slate shingle he just dropped it over the vent. Not sure that’s going to seal it properly especially at the base of the existing vent seal.

 

[doitmyself]

It's hard to say without seeing the assembly close up. Technically, flashing is supposed to work without any sealants. Sealant will crack with movement. Flashing's purpose is to seal areas where there is movement between different surfaces (roof/vent pipe). In this case the roof vents, roof surface, and flashing can all move (up/down/sideways) differently.

This piece should be water tight with no caulk. The vent pipe can move up/down separate from this flashing. The cone that sits above this should seal around the pipe, acting like an umbrella to keep rain out of this flashing top, while allowing everything to float/move.

 

[JC1]

I would want the roofer to take pictures of each boot to see what he did. I hope he slipped the upper part of the boot under each tile.. should be sealed as an upside down U to make sure any water on the bottom can run out.

 

[Malo83]

You need Flexseal.

Flex Seal Family of Products | The Official Store

The easy way to patch, bond, seal and stop leaks fast. Featuring our full line of Flex Seal Products.

flexsealproducts.com

 

[NismoNVT]

loctite PL s30?

 

[PimTac]

Sorry to say but that is a real hack job. You can get some sealant up there to tide you over temporarily but that cut out around the vent stack is just bad. If they had to cut the tile it should have been just enough to clear the stack on three sides.

They used to use a lead sheet pounded in place to form a flashing but my guess is that would be verboten in California. Copper might be a good alternative.

The sun and UV radiation have cooked the sealant and rubber cover.

 

[doitmyself]

Sorry to say but that is a real hack job. You can get some sealant up there to tide you over temporarily but that cut out around the vent stack is just bad. If they had to cut the tile it should have been just enough to clear the stack on three sides.

They used to use a lead sheet pounded in place to form a flashing but my guess is that would be verboten in California. Copper might be a good alternative.

The sun and UV radiation have cooked the sealant and rubber cover.

It seems that you commenting on the old stuff in the first picture? He had new flashing installed to replace that.

 

[PimTac]

It seems that you commenting on the old stuff in the first picture? He had new flashing installed to replace that.

I did miss that. Too bad the after pictures were not the same angle. Then again, getting on a roof is something I don’t do anymore.

 

[Gokhan]

You need Flexseal.

Flex Seal Family of Products | The Official Store

The easy way to patch, bond, seal and stop leaks fast. Featuring our full line of Flex Seal Products.

flexsealproducts.com

LOL No, it's super-expensive and it probably performs worse than average sealant.

 

[Gokhan]

During my biennial roof inspection, the following issue was brought to my attention:

View attachment 115744
There are four of these on the roof. On all four, it appears that someone, at some point, used a copious amount of sealant to seal the rubber donut to the pipe. Of the 4 people who looked at it, the opinions were split: 2 said it was fine, the other 2 thought the rubber boot had failed and the sealant is also starting to fail - so they suggested a "proper repair."

After much deliberation, I hired a roofing contractor to replace all 4 flashings and install new donuts. This is the outcome:

View attachment 115752
View attachment 115753
However, the roofer did not use any sealant during the repair - they just removed the tiles, installed new flashing and slipped a rubber donut down the pipe. I assume the rubber donut is suppose to seal the gap and divert water away from the flashing. Would adding some sealant/mastic to this area improve sealing?

Actually, this is probably OK. The rubber grommet doesn't seem to have any gaps on top, and I doubt water can get in from a gap at the bottom of the grommet even if there is a little gap between the grommet and the sprout of the flashing.

 

[Malo83]

LOL No, it's super-expensive and it probably performs worse than average sealant.

Oh, I don't know it fixed the leak on my kitchen exhaust vent.

 

[andyd]

The doughnut is quick and easy and works without sealants on shingled roofs. The tin boot is the proper one to use on tile? roof. If you need sealants to prevent a leak in the flashing, you're not doing it correctly

 

[Fla]

The doughnut is quick and easy and works without sealants on shingled roofs. The tin boot is the proper one to use on tile? roof. If you need sealants to prevent a leak in the flashing, you're not doing it correctly

X2. I'm in the same house after 40 years and I've never had a problem with the flashing and the rubber boot around my pipes that go through my roof. My solar panels OTOH are a completely different story! They were simply bolted to the roof and there is no seal. They occasionally leak and I have to go up there and put sealant on them. But the sealant dries out and cracks and I have to add more every year or two. The only saving grace for me is that I have to replace the roof about every 15 years so all of the old sealant gets torn off with it and I have to start all over.

If you have properly installed flashing that goes under the singles and a rubber boot then you should be good to go. If you can see daylight around it then it wasn't installed correctly.

Sealant is not a substitute for a correctly installed vent pipe. At most, it's a temporary patch job.

 

[2strokeNorthstar]

It's hard to say without seeing the assembly close up. Technically, flashing is supposed to work without any sealants. Sealant will crack with movement. Flashing's purpose is to seal areas where there is movement between different surfaces (roof/vent pipe). In this case the roof vents, roof surface, and flashing can all move (up/down/sideways) differently.

This piece should be water tight with no caulk. The vent pipe can move up/down separate from this flashing. The cone that sits above this should seal around the pipe, acting like an umbrella to keep rain out of this flashing top, while allowing everything to float/move.

View attachment 115754

Typical roofers. Most will seal everything with tar or mastic and make it worse long term