# Is this an acceptable method of flashing penetrations on a metal roof?



## iLikeDirt (Apr 27, 2014)

Before getting a metal roof done, I'm trying to learn all I can about the process. One thing that mildly concerns me is installations I've seen--including a few in my neighborhood--where roof penetrations are flashed with a surface-mounted pipe boot that screws right through the panels, like this:










This seems slightly dangerous, and, on a standing seam roof, totally defeats the purpose, since each penetration will be accompanied by a dozen screws that will prevent the panel from expanding and contracting like it wants to without enlarging those holes over time and possibly causing leaks.

Instead of using surface-fastened rubber boots, is lapping the panels with a standard metal pipe boot thing an acceptable method of flashing roof penetrations with a metal roof system? Here's a picture:










More broadly, what is the correct method of flashing non-brick-chimney roof penetrations (i.e. pipes) in a manner that will last as long as the metal roof itself?


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## AndyWRS (Feb 1, 2012)

The bottom is the method we use. I would have run the top panel lower to cover up the galv base flashing as much as possible. We get paint mixed to match the roof color and paint all the flashing and pipes so they match the roof. 

I would use the top method only if someone ran a pipe through the roof after the roof was installed. Especially in the case of a mechanically seamed roof. 

I think both are accepted methods, but I would prefer not to put those screws in...eventually they will need replacing with larger diameter ones.


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## OldNBroken (Jun 11, 2008)

AndyWRS said:


> I think both are accepted methods, but I would prefer not to put those screws in...eventually they will need replacing with larger diameter ones.


Sorry, the bottom picture is completely incorrect and the top one is proper. 
The gasket on that no-caulk (which is specifically made for shingle roofs and NOT standing seam) will rot out loooong before the roof has run it's life. It is also a helluva lot of work with more chance of leaking or failure.

Dektite is the only brand I use on a metal roof. There are many others out there but several are very cheap knockoffs of Dektite. 
There is absolutely no reason to be concerned about thermal movement in any 6" area of a metal panel. The screws will not wear out the panel in any stretch of time. 
One thing I see often, though, is people just putting them in dry. The least one should do is run a small bead of NP1 or some other good urethane caulk on the bottom before setting. We always use butyl tape to seal them to the roof. 

We have installed thousands over the years including many on flat metal roofs and the only problem you come across is when it is damaged by someone or something. 

It is by far the best pipe flashing for metal roofs as well as the standard spec on every roofing system out there.


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## AndyWRS (Feb 1, 2012)

That may explain why when I looked at multiple SS manufacturers to see how they show that detail, I found only dektite type details.

I do agree those would take many moons to fail, but we just don't like putting more holes than needed. Can you explain why the bottom detail is flawed. We do it similar to the bottom detail but always run the top panel all the way down to cover the base flashing. The cover panel would be cut out to fit around the jack, sealed and painted to match the roof color for appearance only. The caulking doesn't need to be there as any water getting in around the panel cut around the jack would just run on the flashing and out between it and cover panel on top. Keep in mind, this is S Cal and we get that wet stuff a few times a year. Also, never had a leak at a vent pipe so I'd be curious as to what is wrong with our method.

found a pic:


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## OldNBroken (Jun 11, 2008)

Andy, glad you didn't get all huffy with me before checking it out for yourself. 
The way you do it can be done, it's just not the correct way. As with much in roofing, the final product is only as good as the person installing. You obviously know what you are doing and make it work successfully but the majority of people sadly would fail miserably at it. Not really something you want to teach someone over the internet. You are using the basic detail of any other penetration (skylights and such) and applying it to the pipe. 
The only downside is if you are using no-caulks the gasket material isn't the highest quality and will degrade rapidly on a metal roof. 

Here is a good example of how we do pipes on standing seam, both in the panel and on a rib.


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## AndyWRS (Feb 1, 2012)

Actually I looked it up prior to my original post so I could post a link for the OP...instead I found the Dektite detail on four different manufacturers sites and it got me curious. I am still learning after 20 yrs, I think this is part of what I like about roofing...there is always something new or a different way to do things.

We have one dedicated crew, employees, that do our SS. Most our crews do stone coated metal. My guess is they took the vent flashing detail from stone coated installs and applied it to SS. We started doing SS about 7 yrs ago, but we have been doing stone coated metal roofing since the early 80s. That is where the bulk of my exp as an installer is.

Thanks for the input.

Ironically I thought I had a good grasp of roofing with my 20+ yrs in the business as an installer and manager. It wasn't until I got on these roofing forums that I realized there is far more to roofing than just stone coated metal. I worked for a large company that solely did Decra and expanded to all of CA. Never had to do other products, was buried in work for 15 yrs. Now I am just trying to learn more about all of them now were expanded to the other product lines the last 9 yrs.


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## iLikeDirt (Apr 27, 2014)

Can someone explain to me what makes these Dektite flashings so awesome? I'm just really leery of the exposed fasteners. Is it the material they're made of? The use of butyl tape? Something else?


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## OldNBroken (Jun 11, 2008)

Well then now you can tell your guys to switch to dektites. They are just fine and it will save you a lot on time and labor. Just remember butyl on the bottom and hose clamps on the top. Technically dektite does not warranty it with the clamp but many mfrs require it. Have never had any issues with that either since the mfr is supplying the system warranty, not Dektite.


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## OldNBroken (Jun 11, 2008)

iLikeDirt said:


> Can someone explain to me what makes these Dektite flashings so awesome? I'm just really leery of the exposed fasteners. Is it the material they're made of? The use of butyl tape? Something else?


Well, they are versatile, durable and flexible, easy, quick and neat to install. I've seen the cheaper brands yellow and show signs of drying out after a few years of exposure. Dektite is a very high quality epdm or silicone depending on the application. 
The flange that you screw into creates a watertight gasket around the screws but we add butyl for added assurance. I have literally thousands installed on flat roofs with no issues so I can assure you that, installed correctly, you can be assured they will perform extremely well.


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## AndyWRS (Feb 1, 2012)

OldNBroken said:


> Well then now you can tell your guys to switch to dektites. They are just fine and it will save you a lot on time and labor. Just remember butyl on the bottom and hose clamps on the top. Technically dektite does not warranty it with the clamp but many mfrs require it. Have never had any issues with that either since the mfr is supplying the system warranty, not Dektite.


 If it were up to me I would. Problem is I don't write the checks and he wont change it because we haven't ever had a leak from a pipe penetration.

Hard to argue with the manufacturers install guide though...I may just have to ask why don't we do boots like in the guides.


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## Windows on Wash (Aug 30, 2011)

Dektite boots are what we use when we do standing seam.


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## iLikeDirt (Apr 27, 2014)

If these surface-mounted screw-through flashings are okay for penetrations, can someone explain to me why the same isn't also true of less-expensive exposed-fastener roofs themselves?


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## Windows on Wash (Aug 30, 2011)

The roof boot is considered a maintenance item to be honest. 

That, combined with the fact that most roof boots have a bit more care taken with them than large spans of roofing, means that they tend to be installed a bit more carefully.

The Dektite also has a full width and less compressible gasket and better material on it than exposed fasteners. 

These applications are also combined with a sealant application whereas R-panel and other roofs are just neoprene gaskets that tend to fail when over torqued.


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## AndyWRS (Feb 1, 2012)

Your comparing a couple of hundred screws in flashings to thousands of screws in an exposed fastener install. 

They don't look as nice and will eventually need maintenance. Replacing the boots and screws only on a concealed fastener install vs. replacing the all the fasteners in a exposed fastener install. Your paying more for concealed fasteners, but in long run your doing far less maintenance. You get a better roof with peace of mind with the hidden fasteners. Better warranty, better curb appeal, less maintenance.


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## mako1 (Jan 7, 2014)

All I ever use on any metal roof are Dektites with butyl tape and plenty of screws.Never had a leak just wish they were not so expensive.Bought a 14" (#8 I think) one the other day and it was around $85.This was for a stove pipe so a higher heat rated material.


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## tinner666 (Mar 14, 2005)

Haven't used that rubber/metal boot before. When Oatey was still making No-Caulk collars, we always did them the way of the bottom pic. The No-caulk which have been discontinued were good for 60-100 years.
Now, i still do them that way with the ABS collars and a cap boot on top. Not sure how long the ABS will last, but it's a simple fix if the cap fails. Just slide a new one on.
I've never had a pipe in a seam before.


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## hotrod351 (Jun 15, 2012)

either is good. i just did a metal roof and did the bottom one and the upper pic i used a galvanized flashing instead of a rubber boot one, it get hot here and the rubber isnt going to last that long. but yes thats how metal roofs are flashed.


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