Flashing vent pipes on metal roof?


  #1  
Old 02-26-05, 04:16 AM
tesseract
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Flashing vent pipes on metal roof?

My sister in Orlando needs a new roof and we've been tossing around the idea of going with metal since it will last a lot longer and also not require removing all of the shingles first (I just re-roofed my own house so I'm not looking forward to stripping off shingles again!). I've studied the installation instructions for various panel styles from several manufacturers and everything makes sense except for how round penetrations are properly flashed and sealed when using "PBR", "SM" (aka MasterRib, Classic Rib, etc.) style panels.... I've drove around and looked at metal roofs in my neighborhood, but this hasn't exactly enlightened me. I am a bit of a stickler about doing things the right way so I'd really appreciate it if someone could shed some light on how this is properly done. I'm assuming that merely slopping on some fibered roofing cement or some such is *not* the best way to do this

Thanks!
 
  #2  
Old 02-26-05, 04:54 AM
E
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Allthough it may be allowed to install the steel panel systems over existing asphalt, stripping the asphalt off is recommended. Of course the recommendation is just my opinion.

As for the pipe jacks or pipe flashings, there are pipe jacks designed for these metal panel roofs. They have a neoprene gasket on the bottom of the flange. They are installed with screws driven through the panel. They should be available through your supplier although may be a special order. To check out available configurations, you might try looking up <metalsales colorado > in google. I'm not allowed to post the link here. They offer a list of accessories as well as installation instructions, colors, styles, etc.
 
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Old 02-27-05, 05:08 AM
tesseract
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Thanks for the response, E. Dodge.

Allthough it may be allowed to install the steel panel systems over existing asphalt, stripping the asphalt off is recommended.
I didn't mention this in my original post, but I do plan to use purlins to provide a consistent nailing base for the panels. I didn't notice any soft or springy spots when I walked her roof so it appears the decking is still in good shape otherwise, yeah, I'd tear off the old roof first.

I'm familiar with the neoprene boot pipe jacks you mention, but what I can't seem to figure out is how a *flat* piece of metal (the flange at the base of the boot) can seal a *ridged* hole in the roof panel.

On a related note, why are they so expensive compared to similar style ones sold at the big boxes? I was quoted $30 ea. for the neoprene boot pipe jacks from a local metal roofing supplier compared to $5-$7 for similar flashing at the orange store....
 
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Old 02-27-05, 06:43 AM
E
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Those "special" pipe jacks /"boots" have a plyability to them which allows them to be sucked down tight to the surface, including the ribs.
BUT....I believe flashing pentrations on a metal panel roof is one of the drawbacks to metal panel roofs. They are prone to opening up down the road. But then all roof types have their own individual drawbacks.

Although the metal panels themselves seem "reasonably priced", the accessecories including screws, flashings, ridge, pipe jacks, etc. can boost the total price of total material cost by a guestimate of 50%-100%.
 
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Old 02-27-05, 08:04 AM
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I agree w/E.Dodge, penetrations are the weak point of metal panel systems. The "bendable" pipe jacks work pretty well. I have been told to always install the attachment screws begining at the high point and working dow....sometimes there is a "wrinkle" by the last screw. Best is to design for metal and have all of the penetrations grouped and near the ridge.
Jim
 
  #6  
Old 03-05-05, 03:39 PM
tesseract
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E. Dodge - boy you weren't kidding about the pricing for the panels vs. that of the accessories! I was quoted $2.10/l.f. for 36" wide PBR panel by one local supplier - a very competitive price for here in FL - and $1.75/l.f. for the gable edging. No big deal until you consider that the gable edge is formed from 9" wide stock, so it *should* cost $0.53/l.f.?!?!

I guess this is why so many of the metal roofs I've seen while driving around don't have gable edging!

Thanks for the tips, E. Dodge and Jmorgan1. I'll pony up for the "special" pipe jacks but I think I'll also run a bead of polyurethane flashing cement along the flange before I seat them just in case. Or maybe I'll get lucky and all of the pipe penetrations will land in between the ridges of the panels... Yeah, right. I won't hold my breath on that one!
 
 

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