Author Topic: Help with metal roofing details  (Read 3171 times)

ctmustache

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Help with metal roofing details
« on: August 04, 2015, 07:04:12 AM »
Hi Everyone

Planning an install of Metal Sales Inc's Image II roof panels on my raised ranch. I'm not sure on the appropriate method for interfacing the roofing with the chimney which intrudes about one half of it's width into the plane of the roof. In particular, I'm not clear what I need to do at the top side of the chimney where the roof face meets the chimney. Any one with expertise who can help me?

Thanks!

john6221

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Re: Help with metal roofing details
« Reply #1 on: August 04, 2015, 07:44:55 AM »
What is the width of the chimney? Do you currently have a cricket built behind it?

waffle

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Re: Help with metal roofing details
« Reply #2 on: August 04, 2015, 07:54:58 AM »
Not specific to your question, but I just replaced the siding on one side of the chimney because it was built like this. Water draining off the roof hit that part of the chimney and diverted straight down the wall eventually rotting out the siding.

I still need to do something on the roof so the same thing doesn't happen again in the future. My chimney protrudes about 8 inches into the roof so it funnels a fair amount of water when it rains. I'm just not sure if I should install some sort of flashing to divert the water back towards the main part of the roof or install a very small section of gutter on the side of the chimney.

James

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Re: Help with metal roofing details
« Reply #3 on: August 04, 2015, 08:16:09 AM »

What flashing is on the area already? If it is correctly flashed at this point, your metal roof should work just the same as the current roofing, the flashing does the diverting of water, your metal roof just covers the roof itself. But if it isn't correctly flashed or it needs to be changed that is much more complicated, especially for brick chimneys.

Jack

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Re: Help with metal roofing details
« Reply #4 on: August 04, 2015, 08:19:26 AM »
I think you need to build a chimney "cricket" or "saddle" if there isn't already one there.



Then flash against the vertical faces of the chimney as per the manufacturer directions for your roofing material.

Greg

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Re: Help with metal roofing details
« Reply #5 on: August 04, 2015, 10:07:45 AM »
Usually you use a flashing profile meant for this, attached is a page showing in the lower right corner a 5"x13" version.  Usually you have to buy 10' of it.

ctmustache

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Re: Help with metal roofing details
« Reply #6 on: August 04, 2015, 11:34:31 AM »
Thanks for speedy replies everyone. I am attaching some pictures to better illustrate what I'm trying to do.

There is currently lead flashing at the top of the chimney. Is the suggestion that this remains, or would the flashing that Greg identified replace it?

Jack

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Re: Help with metal roofing details
« Reply #7 on: August 04, 2015, 11:51:11 AM »
The lead flashing would be wrong for a metal roof. Look at page 14 of this pdf. You should probably use the "Cut into sidewall and use Reglet Flashing instead of Counter Flashing" option (in your case, cutting into the mortar joints). But as I said before, you should go find the equivalent PDF for your brand of roofing, and do what it says.

I'd still consider building a little tiny cricket at the leading edge of the chimney, but it's small enough (looks about 6"?) that maybe it isn't worth it. I take that back: if the instructions don't have a flashing detail that covers a pitch sloping down into a vertical wall (and at least the one I linked doesn't), then I think a cricket is the only acceptable option.
« Last Edit: August 04, 2015, 11:58:15 AM by Jack »

ctmustache

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Re: Help with metal roofing details
« Reply #8 on: August 04, 2015, 01:39:12 PM »
Thanks, again!

I'm reviewing the MSI video linked below at 51 minutes, and wonder whether the solution they propose would work here? Although I'd be doing half of what they do given I have fresh air on the other side of the chimney.

https://www.youtube.com/watch?v=WYb16-iuB3Q#action=share

kendallf

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Re: Help with metal roofing details
« Reply #9 on: August 04, 2015, 01:59:57 PM »
If a chimney or other protrusion is under 1' wide, we would typically not build a cricket for it.  In your case, with what looks like about 6" of exposure and open gable edge beside it, I sure wouldn't bother.  I would buy L-shaped flashing designed for your metal roof type.  You can step flash the side of the chimney (like it is currently but using only vertical pieces),cutting the mortar joints and re-pointing afterward, and then put one piece of L-flashing under those pieces.  That would be the cleanest looking solution, I think.  You can even buy pre-formed corner pieces now for the upper and lower corners.

Greg

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Re: Help with metal roofing details
« Reply #10 on: August 04, 2015, 10:07:20 PM »
It's hard to tell from here, but what you are seeing is likely counterflashing that is overlapping the flashing underneath that actually extends under the shingles.  The flashing I referred to would take the place of the flashing that extends under the shingles.  The manufacturer should be able to provide a diagram via the place you bought it to detail this correctly.  Maybe the salesperson there can help.  I know the salespeople where I get my metal roofing (I do metal roofs as part of my design/build practice) are super helpful and enjoy helping me with interesting projects.

In your case you'd flash up the roof under your metal panels and the flashing would extend 5" or so up the side of the chimney, and then you'd install new counter flashing to overlap that.  The counterflashing is usually set into the mortar a little bit.  In your case, if it is lead, you may be able to bend it up out of the way and install new flashing, then bend the existing counterflashing back down to cover the top edges of the new flashing.  Hope that helps!