Pipe flashings for metal roofs

[Dr_Snooz]

Hi everyone. I'm taking a risk asking a somewhat off-topic question, and I hope you won't hate me too much for it. I need to re-roof my house and plan to use metal R-panels instead of the 3-tab shingles I have now. I'm looking at the rubber boots that I'm supposed to use for pipe flashings, and frankly, they give me the creeps. I just don't see how a rubber boot, a thousand screw holes, sealant, and hope will keep water out for long. I like the Excel chimney flashing that a lot of you recommend, and will use it for my woodstove flue. The problem comes in flashing my other pipe penetrations. Does Excel make flashings for 1-3/4" ABS vent stacks, 1/2" electrical conduits and other non-wood stove pipes? Does anyone?

My temptation is to buy regular galvanized flashings and bend them to work like an Excel flashing. I'd trust my homemade jobs more than those boots, but it's a gamble. It looks like there might be some roofers on the board, so that's why I'm asking. Anyone have advice for me? Thx

 

[Wooden Head]

Hi everyone. I'm taking a risk asking a somewhat off-topic question, and I hope you won't hate me too much for it. I need to re-roof my house and plan to use metal R-panels instead of the 3-tab shingles I have now. I'm looking at the rubber boots that I'm supposed to use for pipe flashings, and frankly, they give me the creeps. I just don't see how a rubber boot, a thousand screw holes, sealant, and hope will keep water out for long. I like the Excel chimney flashing that a lot of you recommend, and will use it for my woodstove flue. The problem comes in flashing my other pipe penetrations. Does Excel make flashings for 1-3/4" ABS vent stacks, 1/2" electrical conduits and other non-wood stove pipes? Does anyone?

My temptation is to buy regular galvanized flashings and bend them to work like an Excel flashing. I'd trust my homemade jobs more than those boots, but it's a gamble. It looks like there might be some roofers on the board, so that's why I'm asking. Anyone have advice for me? Thx

What is the pitch of the roof? Will you have snow and/or ice?

 

[zrock]

the rubber boots have been used for a long time with no issues.. I have them on my place and never had a leak.. This is where it pays to hire a professional if you are uncomfortable with it. I have installed them and its a game of patience to get them right

 

[Dr_Snooz]

Sorry, it's a 3/12. And no snow.

 

[Boil&Toil]

I need to re-roof my house and plan to use metal R-panels instead of the 3-tab shingles I have now. I'm looking at the rubber boots that I'm supposed to use for pipe flashings, and frankly, they give me the creeps. I just don't see how a rubber boot, a thousand screw holes, sealant, and hope will keep water out for long.

1000 screw holes is 980-994 too many, so that might be your problem.

Using the correct boot material (EDPM rubber) and correct sealants (butyl or polyurethane) they work. I'm well past a decade on my plumbing vent sealed (to my metal roof) with one and about eight or twelve #6 sheet metal screws, IIRC - never an issue. Just careful installation work and the right parts. I didn't apply any hope, just a careful look underneath during rainstorms. I did clean the roof carefully before applying sealant and boot.

Due to sloppy contractor work before that I did have to go over the entire roof, loosen every screw, (hundreds of them) seal it, retighten it. That has also held the same period of time, as I did the plumbing vent when I was up there for that job. Too hard to isolate exactly which screws were done wrong and leaking, (since the leaks can run along the framing) but now they don't leak.

 

[bholler]

I agree don't use the rubber boots just get standard flashing and cut it in not a big deal at all. The smaller ones fir vents etc are certainly less problematic that the chimney ones but still wouldn't be my choice

 

[Wooden Head]

Sorry, it's a 3/12. And no snow.

Should not be a problem. Follow instructions. Mine instructed to put screws 1 inch apart. the installer opted for every 4 inches. The second year on a 12/12 pitch in the far north the snow/ice slide ripped it off. When replaced I followed the instructions and have not had aproblem in 10 years.

 

[Dr_Snooz]

Sounds good. I'll use the boots. I can always do my own thing if they fail. Thanks everyone!

 

[Dr_Snooz]

Okay, I'm back with more questions. I appreciate your patience. If I'm going by the responses here, the rubber boots do have problems, as I expected. I've worked in construction long enough to know that rubber is fragile and sealants fail. To the extent possible, you keep those things out of direct sunlight. From the metal roofs I've observed, the first thing to fail is the neoprene seals around the screws, and they fail long before the roof panel shows signs of wear. (These were shed roofs, so they didn't have boots for me to inspect.) The screw seals are relatively shielded from weather and UV, whereas a rubber boot is getting the full blast of both. Our summers here get up to 115°F, and UV levels sit solidly in the "Hazardous" zone for months on end. I know that any sealant exposed to our UV levels will fail in 1-5 years. When I seal windows and doors, for example, I always put a bead behind the trim as a backup for when the outside bead fails. A bunch of flimsy rubber boots on a roof deck in those conditions seems like a guaranteed replacement project every few years, followed by another project of repairing water damage inside. I'm probably over-thinking it, but not by much.

Leaving that all aside, it still seems like there's a continuum of thought on the board here. When we're talking about woodstove flues, the agreement is that rubber boots are a bad idea (https://www.hearth.com/talk/threads/chimney-pipe-flashing-boot-for-metal-roofs.178356/). Yet when we're talking about vent stacks, they're okay. Thus, as we move down in size and heat, there's a point where rubber boots become the better choice. So if the Excel flashing is right for my woodstove, is it also right for my furnace flue (7" OD)? What about my water heater flue (3-1/2" OD)? How about my furnace fresh air supply (4" OD)? For you guys with metal roofs, how are these items flashed on your roofs? Have you experienced any problems with them?

Thanks again.

 

[EatenByLimestone]

On the roof I recently finished, the building is on piers. My plumbing vent actually went up the outside of the building, through the soffit, and out the roof. I rerouted it so I could eliminate the penetration. That’s not possible for most applications.

If it was my roof, I’d put ice and water over the entire roof deck. I’d lay it up right around the vent and make sure it seals well. The vent isn’t going to get hot. I’d then flash as normal. If the normal flashing failed, the ice and water shield will be there to run backup.

There are rubber replacements that you can slap down over the vent pipes when the rubber fails. I’ve secured this with silicone with good luck. Paint will give a bit of UV protection to the rubber also.

 

[SweptNZ]

Hi everyone. I'm taking a risk asking a somewhat off-topic question, and I hope you won't hate me too much for it. I need to re-roof my house and plan to use metal R-panels instead of the 3-tab shingles I have now. I'm looking at the rubber boots that I'm supposed to use for pipe flashings, and frankly, they give me the creeps. I just don't see how a rubber boot, a thousand screw holes, sealant, and hope will keep water out for long. I like the Excel chimney flashing that a lot of you recommend, and will use it for my woodstove flue. The problem comes in flashing my other pipe penetrations. Does Excel make flashings for 1-3/4" ABS vent stacks, 1/2" electrical conduits and other non-wood stove pipes? Does anyone?

My temptation is to buy regular galvanized flashings and bend them to work like an Excel flashing. I'd trust my homemade jobs more than those boots, but it's a gamble. It looks like there might be some roofers on the board, so that's why I'm asking. Anyone have advice for me? Thx

Hi, chimney sweep and logfire installer from New Zealand. We've been using metal corrugated roofs on our houses for 150+ years.
Very common here for roof penetrations (chimneys, exhaust vents, overflow pipes etc.) to use Dektite rubber flashings.
The one we commonly use is a Dektite 605 which suits 10" (250mm) - 14" (350mm) and they're rated for -50C up to 115C and 150C intermittently.
If you youtube that particular product there are a few videos to watch. You start from the top/high side in the center with roofing screws, silicon, and work your way around. You put a bead of silicon on the inside of the boot that connects to the chimney liner, then a final bead on top. If your outer liner has a seam, you seal the entire first seam up to the next liner join.
These flashings are guranteed for 15 years, but will last 20-25.

 

[bholler]

Hi, chimney sweep and logfire installer from New Zealand. We've been using metal corrugated roofs on our houses for 150+ years.
Very common here for roof penetrations (chimneys, exhaust vents, overflow pipes etc.) to use Dektite rubber flashings.
The one we commonly use is a Dektite 605 which suits 10" (250mm) - 14" (350mm) and they're rated for -50C up to 115C and 150C intermittently.
If you youtube that particular product there are a few videos to watch. You start from the top/high side in the center with roofing screws, silicon, and work your way around. You put a bead of silicon on the inside of the boot that connects to the chimney liner, then a final bead on top. If your outer liner has a seam, you seal the entire first seam up to the next liner join.
These flashings are guranteed for 15 years, but will last 20-25.

The ones you have available must be better than what we have. I replace quite a few between 5 to 10 years. Where the metal flashing easily outlasts the chimney.

 

[MedicineMan4040]

New metal roof coming in two weeks.
Two layers of shingle roof to be removed.
Current flashing attached. Selkirk vented, and their instructions are to use a vented flash around the chimney flue.
I spoke with the roofing people. They use a rubber boot and always have.
I just spoke with the chimney flue installer. He said just tell the roofers to go over the flashing job he did with the metal roof
and be done with it. I kinda like that answer. The current roof penetration doesn't leak (it's easily checked from the inside).
Not seen with the image attached is a storm collar that goes over the vents you see.