Stove pipe flashing on corrugated metal roof.

[Kenster]

We had a new roof installed on our house recently after a hail storm. A metal roof with slight corrugation.
I'm not sure that they installed the flashing collar around the stove pipe correctly. The collar is attached to a flat panel which they screwed (or riveted) down to the roof panel, then filled the gaps with really thick silicone caulking. I'm thinking that the uphill side of the flashing should have gone UNDER the roofing panel and the downhill side of the flashing should have gone on top of the panel. But the whole thing is on top. If the roofing panels were flat it wouldn't matter too much but the corrugation creates gaps between the roofing panel and the flat flashing of the collar.
It would have been nice to have a flashing that matches the corrugation of the roof.
I'm worried that, over time, those thick globs of silicone caulking on the uphill side are going to deteriorate and water will stream in through those gaps. The caulking job on the uphill side is just a mess. And there is no caulking over the rivets that hold the flashing panel down to the roof, nor any sign of gaskets under the rivets.


The roofer has been great to work with so far. I've been traveling and just inspected the flashing installation yesterday. We have a $4000 hold back pending completion to our satisfaction. I'm pretty sure we can get him to do the job correctly. I just need to know exactly HOW that should be done.
Plus, there are many homes out here that need new roofs and ours is very visible. He's been using our roof as a model for potential new customers. I'm sure he'll want to do right by us.

Any thoughts or suggestions would be appreciated. Especially from pro roofers or stove installers.
Cheers!

Ken

 

[begreen]

That looks like a standing seam roof, not a corrugated one. There is a special flashing by Excel that would have been a better idea here.

 

[Heatsource]

silicone sandwiched between metal wont really deteriorate, probably be a water tight job for-ever
that said, a lead soldered flashing, or rubber boot style might have been more professional.

 

[Kenster]

That looks like a standing seam roof, not a corrugated one. There is a special flashing by Excel that would have been a better idea here.

It is a standing seam, but the individual panels are not flat but have low corrugations so they do not sit flat/flush on the roof decking.

 

[begreen]

Here's the ICC Excel flashing on a metal roof. This is before the storm collar was put on.

(broken link removed to http://www.icc-rsf.com/main.php?t=chem_produits&i=95&l=en)

 

[Kenster]

Begreen, does that work just as well if the flashing does not tuck under the ridge row? Our stove is well down the roof from the ridge.

 

[begreen]

Take a look at the instructions in the provided link. It slides under the roof in a slit cut on the upper side and overlaps the roof on the bottom side.

Whatever you do, replace the current rusted storm collar that is up there.

 

[Kenster]

Ah, I see it more clearly now. I was picturing that raised 'box' all the way around but it's actually a flat panel on the high side, tucked into a slot under the roofing panel.

 

[bag of hammers]

If you were up in the snowy parts, I'd also suggest a cricket of some form. I think this was one of the reasons my neighbor's chimney got wrecked last winter (close to eve, metal roof, sliding snow, etc.). Guess you don't have to worry too much in the Houston area, but I wonder how many folks with metal roofs don't consider this...

 

[jeff_t]

Some pics sent to me by webby showing proper installation of the Excel flashing. My install wasn't this elaborate, as it tucked up under the ridge cap like in begreen's pic.

 

[webby3650]

If you were up in the snowy parts, I'd also suggest a cricket of some form. I think this was one of the reasons my neighbor's chimney got wrecked last winter (close to eve, metal roof, sliding snow, etc.). Guess you don't have to worry too much in the Houston area, but I wonder how many folks with metal roofs don't consider this...

It is definitely something to consider. I have had to do a few repairs due to sliding snow. A few chimney suppliers offer one. (broken link removed to http://www.icc-rsf.com/main.php?t=chem_produits&i=22&l=en)

 

[Kenster]

I think the roofers did not want to have to remove the stove pipe in order to slide the uphill side of the flashing under the roof panel, so they just removed the cap and slid it down the chimney. It may work just fine but I wish the high side was tucked under the panel.

 

[Holiday]

I used excel flashing and it worked very well. I just didn't caulk the low side to allow water to run out if some ever did get in there. The high side should definitely be tucked under with any type of flashing on a roof.

 

[webby3650]

I used excel flashing and it worked very well. I just didn't caulk the low side to allow water to run out if some ever did get in there. The high side should definitely be tucked under with any type of flashing on a roof.

We have had driving rain blow up under the bottom side, that's why I caulk it. If water did find its way in there, its coming down the pipe either way.

 

[Holiday]

Good point.

 

[begreen]

I was wondering if you could leave a couple weep holes on the bottom edge to slowly drain any accumulated rain or condensation moisture? They wouldn't need to be that large. Maybe 1/8"?

 

[bag of hammers]

similar to weep holes - could you do something like I've done on a sill plate or door threshold flashing pan? - caulking in a pattern with a couple small "breaks" to allow any trapped water to run out? same sort of idea - not sure if that makes sense here. Once water gets up under flashing it can go all over (on a shingle roof anyway - not sure if that applies to metal roof).

 

[begreen]

Yup, same idea.

 

[mfetcho]

I used a flashing similar to the ICC that Begreen mentioned. It was on my cabin that has a delta rib roofing. I cut a slit in the top side and slid the flashing under the roofing. I cut the mating ribs in the bottom side. I used a roof sealer to fill any gaps. 5 years and not a leak.

 

[cableman]

Probably would have been better to use the self leveling sealant you find on top of rv roofs. Or check out the sealing tap that goes around the exterior of a new window install.
My job uses bishop tape, this would work well! The sun alone would seal this stuff once it was laid over the flashing and roof.