I have a L-shaped building with a 5/12 roof. On the inside of the L there is a 1/12 almost flat roof. We are wanting to cover it all covered with metal. I don’t know what the metals called but it’s the same type you see on traditional metal buildings.
My problem is that when it rains the water will come down almost perpendicular to the one side of the flat roof. I don’t know how we will keep the water from traveling across the valley and underneath the metal. We can’t just use silicone because of the ridges in the metal.
Is there a special valley detail that would solve this problem?
Replies
Hi Kyle,
Is there a special valley detail that would solve this problem?
Yes there are a multitude of ways to do this but it's necessary to know what you may typically be dealing with.....such as huriccanes, snow, local area inspections minimum pitch requirement, metal roofing manufacturers minimum standards, upfit pieces etc.
If you'll fill out your profile we can begin looking into this.
Thanks,
Pedro the Mule - Attack life at the right angle
I'd be curious to know what all those methods might be.I can only think of two and would not be real confident with either of those on succh a low pitch
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Hi Piffin,
I've not had to deal with extreme snow loads but have had to deal with high potential winds driving rain.
I've always backed my metal roofing installations with 30 lb black felt and triple layered any valleys over the primary layer of felt and made the 2nd layer a hand applied aluminum flashing.....I expect a product like the Grace bituthene membrane would be as good or better but my process has yet to ever fail and is affordable.
I run the valley piece a minimum of 12" up and around where the main panels will intersect. I then use flat crimps to ever so slightly curve the top edges of the valley down and before screwing down the valley I lay down strips of roofing caulk downhill and under the top of the lip. Press the valley in place and screw it down. You should have generous squeeze out and this should be smoothed out such that if water ever hits it, it'll divert the water down the edge.
From there install the roofing as usual and take all the time necessary to cut the roofing in neatly towards the valley. As I'm installing the main panels where they run over the valley piece I use a neoprene foam strip embedded in roofing caulk under each panel about 3" back from the end of the panel.
The idea with this is that all metal roofs leak at some point, but that when it does leak, the water is efficiently diverted out of the bottom of the roofing without backup up into the home. Thus this situation doesn't eliminate leaks, it controls what happens when it does. So far I've not experienced leaks just as I've never experienced leaks in my basement. It's the attention to carefully handled details along with a backup plan of what to do with unwanted water.
Other options are building an underbedded drain pan with exit through the side of the house, or building the valley up which may or may not be an option depending on existing layout, or a custom crimped and soldered valley panel onsite with factory paint to match. There are so many ideas to deal with but I didn't know where to start without more detail on his situation.
Pedro the Mule - Not wet hooves or fur here
I would need to see to understand all those details, but it sounds like you are primarily relying o using 30# backup to direct leaks and caulk to prevent most of them.Which is not what I'd consider leakproof on a 1/12Might ork most of the time, but I wouldn't ant to put my name on it
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Hi Piffin,
relying o using 30# backup to direct leaks and caulk to prevent most of them
Well the neoprene foam under the lips of the upper panels edges and multilayers in the valley are indeed what is being relied upon as well as multiple continuous strips of caulk all the way up the valley pan. The multiple strips simply mean that if water just happens to get past the first layer, which it shouldn't if done correctly....that the second, third fourth etc. will catch it's upward movement and redirect it to daylight.
It's simply a work around that I've experienced reliability from in a situation that the roofing manufacturer wouldn't warranty. I definitely wouldn't rely upon it directly on the coast nor in snow load country but I've bet several shops on this and it's never failed....3 of these shops were open ceiling so I even checked up on them during a few storms just for fun.
But alas I do agree that putting your name on such an unwarrantied installation is risky in the least. I've also done similar helping a friend install a solar system on a shed roof addition to his house. He's been there 7 years without a leak...again agreed that it's not the best sleep you'll ever get but so far so good!
Pedro the Mule - Now let's see if he can get us some photo's and a location
A picture would help, but you are dealing with odds against you on suh alow pitch and that style roofing
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Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Here is a picture. I guess it's worth a thousand words. I hate to type so I guess I should have sent it first.
I don't like the idea of having to rely on felt. I've always "felt" that if you have to rely on the backup then the primary way can't be right. However, it is better then most of the ideas I've heard over the last few days. I've talked to several people that do metal roofing for a living and I believe most of them to be hacks that can't really hold a job doing anything else. I'm sure there are a lot of geed ones, just not any that I know.
FYI, I'm in Oklahoma City and we regularly get rains 60 - 70+. That's why this is such a big deal.
Thanks for the help.
Kyle
That's not a picture - that's a drawing. It's only worth about 500 words.
The 1st question is what kind of metal roof and what are the specs on it? Some products can go down to 1/12. Many can't.
http://www.quittintime.com/ View Image
Also, when we do metal roofs, we use this detail for the valleys:
http://www.grantlogancopper.com/shop?page=shop.product_details&flypage=flypage.tpl&product_id=90&category_id=22
The bottom of each pan then locks into the receiver on each side of the valley.
http://www.quittintime.com/ View Image
The 1:12 section pretty much has to be flat soldered seam copper to not leak. Stay away from lead-coated copper because it has a nasty tendency to develop pinholes. Those flat seams ought to terminate above a common valley with the 5:12 section and the valley metal should have an upwards 'vee' bent into the center of it (actually called 'W' flashing) -
View Image
to prevent water flowing up into/onto the 5:12 section - you may need to bend this 'vee' to a height of 1" or more to be effective.
Jeff
Edited 8/4/2009 10:07 pm ET by Jeff_Clarke
Jeff ,
Could you explain what you mean about lead coated copper developing pinholes ??
Thanks , Walter
Roofers in our area tell me that they have generally moved away from LCC (to TCS if gray is desired or copper) because of this.
In terms of finding support for this (which usually involves pinhole failures in older flashing) on line - not much available - I'm reporting what the roofers tell me.
http://books.google.com/books?id=ClnQtqipTtsC&pg=PA575&lpg=PA575&dq=lead+coated+copper+pinholes&source=bl&ots=EGvnGt3i08&sig=Ke3NWECBk1IM691qqfStVaCtJjQ&hl=en&ei=y3h5SuPBFoKGtgfMptmWCQ&sa=X&oi=book_result&ct=result&resnum=7#v=onepage&q=lead%20coated%20copper%20pinholes&f=false
http://www.library.cornell.edu/staffweb/kaleidoscope/volume8/sept99.pdf
Jeff
jeff,
I'd be more inclined to think the shift to Freedom Grey or TCS has more to do with there being no lead in the product , not because there are problems with the material.
Any copper can wear due to " erosion corrosion " .
description can be found in the CDA books and website too I bet .
I think the pinhole reasoning is suspect .
Walter
Several of these cases have been on my projects. I've stopped specifying LCC for this reason.
Jeff
Jeff,
The article about 65 year old leader pipes developing pinholes doesn't surprise me . Thats a display of erosion corrosion at work over many years .
http://en.wikipedia.org/wiki/Erosion_corrosion
Walter
I'm really curious about the pinholes in leaded CU. Never heard of it and can only image it in some strange chemical situation or a bad batch of material to begin with.
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How do you handle the upper end of the valley flashing when there is a large V in it? Especially when two valley flashings intersect such as on a dormer?