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Metal Roofs


Bain
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Does anyone have expertise when it comes to metal roofs? I looked at one today that was less than a year old that has severe leakage problems, both in the valleys, and along the peripheral edges. You can see that the contractor has gooped on a bunch of rubber along the valley seams, but of course that's a temporary fix. What detail was likely screwed up when the roof was installed that necessitated the ugly repair?

Insulation prevented me from seeing much from within the airspace above the lay-in ceiling.

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How close were the fasteners to the valley centerline/ overlap? If any fasteners are near the valley overlap, water could be running between the roof panel and valley metal, and seep in there.

Otherwise, I agree with Erby.

About the only places that style of roof is installed around here is on shops/ outbuildings, because they tend to leak.

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Bain, the screws that line up just inside either side of the valley flashing aren't supposed to be there. It will definitely leak. The patch is an attempt to remedy that mistake. Decking is needed to support that flashing. It's true that many steel framed structures used metal panel roofing without roof decking successfully but that's because they didn't try to incorporate valleys like this one has. You've got to have decking for a design like that if you're going to use metal panel. I agree with you that the patch is temporary. It's an error in roof design and will always be a problem until it gets back on the drawing board. You just can't combine any building material with any building method and get good results.

Marc

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Ah, got you. I don't see many metal roofs, but knew I could find help here. The exposure of the valley flashing occurred to me, but it looked fairly normal. I think the fasteners are the fatal flaw.

Brandon, I always trash metal roofs--I see them on houses, infrequently--with exposed fasteners. This roof was on an equine veterinary-center buildng. The majority of the structure was an immense evaluation track, but there were two small offices attached, as well. I've looked at several houses for the CEO, and he asked me to to check out the roof to see what was up. What's the consensus? Rip out the yuck and begin anew?

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What's the consensus? Rip out the yuck and begin anew?

Yep. I did the same thing for this new Vet Hospital earlier this year. Notice the barrel roof in front. It leaked into the reception area before he even finished moving in.

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Marc

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Bain,

Here is an installation guide for a similar system. it is available on their website at:

http://www.metalmanroofing.com/installation-guide.pdf

it has a good valley detail that will help you understand the assembly. If I was going to take a guess what is going on I suspect they left out the closure strip and are trying to compensate with the reverse lap black gunk shown in your photos.

R

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John, what's the pitch on that thing? It looks awfully shallow. If I'm right there is likely additional detailing for low slope configurations that you should be looking for, if the manufacturer even allows that panel on a low slope application. The Z flashing where the roof pitch changes will leak too, never seen one that didn't.

I don't get horse folk. They'll spend a fortune on their animals but cheap out on building materials. If that were my building the roof would be standing seam, bent to follow the change in pitch, with soldered flat locks at the valley.

Tom

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John, what's the pitch on that thing? It looks awfully shallow. If I'm right there is likely additional detailing for low slope configurations that you should be looking for, if the manufacturer even allows that panel on a low slope application. The Z flashing where the roof pitch changes will leak too, never seen one that didn't.

I don't get horse folk. They'll spend a fortune on their animals but cheap out on building materials. If that were my building the roof would be standing seam, bent to follow the change in pitch, with soldered flat locks at the valley.

Tom

Tom,

The slope was fine above the evaluation track, but between 2/12 and 3/12 on the portion above the office space. That concerned me, which is why I took the photos below. I need to Google some installation instructions to find out what's kosher and what isn't. You're right about the standing seam roof, but for a building this size, installed by someone with a reputation, the cost would have been 80-100 grand around here.

I know, I know . . . but sadly it all comes back to the bucks.

Thanks for the link and the .pdf, Rocon. I'll definitely take a look.

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The NRCA recommends a minimum slope of ½:12 (4 percent).

Building Envelope Design Guide - Roofs. Scroll down to METAL PANEL.

Marc

Thanks, Marc. You've been very helpful on this one.

I posted a query on the forum Mike suggested, but so far no response. When one asks a question, only one photo can be posted, so I made five separate posts. Maybe I ticked those good ol' boys off. Something tells me they aren't gonna provide much more useful info than youse guys have.

http://www.metalroofing.com/v2/forums/i ... tegoryID=1

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Another possible problem there that's partly pitch-related is that water can easily blow uphill on metal panels, and enter under the ridge cap. The ridge cap profile they used rides along across the high spots on each panel, rather than notching around those high spots and dropping down to the main level of the panel. They are supposed to bend the panel ends up at 90 degrees at the top, to create a dam, but may not have done that. The lower the pitch the more likely this will be a problem when it's windy.

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that the patch is temporary. It's an error in roof design and will always be a problem until it gets back on the drawing board. You just can't combine any building material with any building method and get good results.

Marc

I agree with Marc and Erby. Any change in slope where there is a seam is a potential leak. It's a good bet water hits the valley and runs right over the top of the valley flashing.

They could have folded a lip into the upper edges of the valley metal to stop that runoff from overflowing the valley.

Then every screw below that lip is a potential leak. Screw holes get stretched by the expansion and contraction of the metal, so they have no place in a valley full of water. [:)]

It can be fixed, but with new metal and solid decking in the valley.

It's just a horse barn, but it's brand new horse barn, so no excuses.

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  • 5 weeks later...

A metal roof can be a challenging roof surface to seal from the elements. One of the major factors is the constant expanding and contracting of the surface itself. A metal roof can expand and contract as much as 2 inches every 100 feet which can be devastating to fasteners and seams, which 90% of all roof leaks occur at these points.

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Hey Bain,

That's obviously a metal building. While a sales rep and conceptual designer for a Design/Build Contractor in the 80's we sold and constructed Butler Metal Buildings. We put up a ton of them for car dealerships, body shops, horsey folks, etc. Somewhere on the exterior or interior of the building will be a tag or emblem identifying the product manufacturer (typically in the gable or at a corner). I'd recommend that your client go directly to them.

Some metal buildings come with amazing warranties. Butler's was - are you sitting down? - 25 years - not pro-rated. You can rely on the fact that the sales representative in your area, if he's smart, doesn't want anyone out there saying bad things about his product. You know how it goes - one unhappy customer will say more than ten happy ones. It's probably the client's best and most affordable way to get the problem truly solved instead of band-aided.

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