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Bzzzzzt
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# Posted: 7 Jun 2014 18:01
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I'm building an addition on my cabin and I built a lean-to roof that has about a 12 degree pitch. My pitch angle calculator says that is about a 2.5/12 pitch. I decked it with regular OSB roofing sheets and put 15# felt on it for now.
I was at Lowes yesterday and they had some Ondura roofing panels in brown or red that sort of resemble metal roofing but they're a composite of some sort. I was thinking of going with a metal roof or the Ondura due to the low slope of the roof.
My question is for anyone who may have any experience mating a metal or Ondura roof system into asphalt shingles on the original part of the cabin that has a 16/12 pitch. How do you get the shingles to allow water to flow over onto the courigated roof without having gaping holes that you'd have to caulk or something? I'm sure there's something made for this purpose but I didn't see anything at Lowes and this particular store is not staffed by people who know the difference between.... (fill in the blank with your favorite coloqulism.)
Any point in the right direction would be appreciated.
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bldginsp
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# Posted: 7 Jun 2014 21:43
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In general you want to get as wide a metal flashing as you can under the underlayment of the asphalt shingles, which then overlaps the metal or other roofing.
This flash is called a transition trim and you'll find a good section showing how to install it on page 16 of this PDF, although that section is for a metal to metal transition, not an asphalt to metal transition:
http://www.bestbuymetals.com/pdf/r-panel-installation-guide.pdf
That section does not show placing the trim below the underlayment because it's describing an all new metal roof instal, but whenever you transition from any shingle you want to get your new flash or underlayment under the shingle underlayment, because shingles are not a completely positive water barrier (like metal roofing should be, as a continuous sheet).
The flashing overhanging the lower roofing will leave a gap above the roofing due to the ridges in the roofing, you can install closure pieces to take up the gap to keep the wasps out, or just let it be. It's not a large area so won't attract squirrels or birds.
On any low slope roof it's best to double up your underlayment and use 30 lb. felt, unless the manufacturer's instructions say otherwise.
Show us some pics!
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BaconCreek
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# Posted: 8 Jun 2014 18:13
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We were looking at Ondura for the cabin roof but if you google it there are several lawsuits pending regarding the durability of the product. We went with metal.
We did use ondura on a firewood storage area. Works fine.
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KinAlberta
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# Posted: 9 Jun 2014 22:04 - Edited by: KinAlberta
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Yeah I briefly looked at Ondura on the internet and a number of fairly legitimate sounding posters didn't speak well of it at all. The manufacturer needs to step up and state it's limitations.
That said, I've heard that newer asphalt shingles aren't performing very well either and a major mfr has a lawsuit against it for delamination or something ( and separately about 15 yrs ago someone told me that the old 15 yr shingles lasted long enough that the mfrs cut quality/costs by calling those old 15 yr rated shingles 25 yr shingles, then the old 25 became 35, and so on..)
And... Recently I heard that the newer cedar shake roofs aren't lasting as "consistently" well as they used to since younger trees / newer growth stock is being used.
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Bzzzzzt
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# Posted: 20 Jun 2014 23:12
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Well I bit the bullet and went ahead and bought enough Ondura to do my addition. I also bought some 20" flashing and I have enough of the old shingles to cover up the flashing over the top of the Ondura. We shall see how it works.
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rayyy
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# Posted: 21 Jun 2014 07:41
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I did my first house with that.It was junk from day one.You cant walk on it.The sun ruin's it.It looses it's color in a few years.I had to rip it all off and re-shingle it in 5 years time.
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Bzzzzzt
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# Posted: 21 Jun 2014 14:03
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Well Rayy, I was hoping that they had improved it some since all the bad reviews I had seen on it were from 2001-2003 but even though it went up really quickly and easily, when I went back to put the flashing on I walked on it and crushed a spot so that it tore open. I'm gonna have to get another sheet to do the rake anyhow so I'm gonna try and put a couple of ridges over that spot. Other places where I had to walk looked like if I had spent too much time there they would have acted similarly.
Initially I was impressed with this roofing but I think I'll reserve judgement until after it comes a good storm.
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Smawgunner
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# Posted: 21 Jun 2014 19:04
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I put it on a woodshed but wouldn't use it on a home.
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Bzzzzzt
Member
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# Posted: 1 Jul 2014 15:31
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I bought another sheet to do the rake and an aditional sheet to patch the spots I had crushed. I cut the sheets lenghtwise the entire length with 2 or 3 ridges and placed them under the flashing and covered the entire section where the bad spot was. You can't hardly see where it's patched because it just looks like the rest of the roof. I will have to keep an eye on it and see how it does but so far it hasn't leaked.
At the cabin I have a neighbor who is a contractor and when he saw the Ondura in my truck he told me that it was "good stuff." I guess I'll have to wait and see what the future holds.
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