(1) Flat or striated panel (2) thinkness of roof decking

Chapel Oaks
2/23/2008
We are building a retirement home in the North Texas area that will have a standing seam metal roof. We intend to live in the home for some time. The roof is pretty simple with no dormers or valleys. I have a couple of questions that I would like to submit for answers. QUESTION 1 The roof will be 24 gauge standing seam material. One vendor quoted a striated roof and one vendor quoted a flat panel roof. In discussing the striated panel with the vendor that quoted the flat panel, he would offer a striated roof at no additional charge. The question I have is will “oil canning”, which is common trait with metal roofs, be less obvious and less of a problem with a striated panel than with a flat panel. QUESTION 2 The second question is I was initially told that I need to make sure the roof decking was 5/8th inch plywood so they can screw into the roof decking. In pricing the 5/8th plywood decking cost, it is significantly more than 7/16” plywood or 7/16” OSB. I have since told that 7/16” plywood or 7/16” OBS be sufficient for roof decking for a metal roof. I am securing the cost difference from the lumber company but I understand the cost difference is pretty substantial. Reading between the lines, I think 5/8th decking will cover flaws, such as dips or waves in the roof ,better than 7/16th material. The question that I would like to ask, should I use 5/8th material or 7/16" for the roof decking for a metal roof? Chapel
Guest User
2/23/2008
Chappel Oaks, It used to be that most manufacturers required 1\2 inch cdx plywood, but now most everyone uses OSB. 5/8 inch cdx does make a stouter deck, it just depends on what you are willing to pay for. Personally, I have 5/8 cdx on my home. I believe it is worth the difference and I've roofed for 36 years. As for as oil canning, it is inherent in all metal panels, some you can see better than others. I would use a 12" or 16" panel to keep it to a minimum. As for as the striations, it might keep the oil canning down but I have seen the oil canning in panels with and without the striations. The striated panel should not cost any more than a flat panel. We make our panels on the jobsite and we can make them either way. It is just a matter of lowering the forming rollers that make the striations. In most commercial work we do the blueprints call for a non-striated panel. [email protected]
Todd Miller
Isaiah Industries, Inc.
3/1/2008
Thanks Wade!
Brian Selig
Architectural Building Components Metal Roof and Wall Panels
3/1/2008
The thickness of the deck is usually determined by UL-580 uplift testing. Most panels are tested on 5/8" plywood, but there are more choices available now for thinner decks. OSB is far more vulnerable in this aspect. See a UL-580 construction number for the product that you select to decide. I always recommend striations. They're free and the pattern is not as overwhelming in installed form as it appears in samples. Contractors are trained to recommend them to avoid controversy with less knowledgable homeowners (and occasionally architects!).
Guest User
5/12/2009
Why are striations recommeded? What do they do for the roof as to maintenance, looks, weatherization, reflectivity, etc a flat panel does not?
Guest User
5/19/2010
I want a flat panel standing seam installed and the roofer that has bid the work wants me to sign a waiver if I use the flat instead of the striation. He says they can't guarantee the work if I use flat because of the "oil canning" problem. I'm in central texas and the oil canning I suppose could be a problem but I cant imagine spending the extra money for the metal roof and then signing a waiver. What do you think?
Nate Libbey
5/20/2010
gene, It is normal to have you sign a waiver stating that you understand it can oil can. But... oil canning is not a structural flaw. It doesn't increase the chance of the roof leaking or performing worse than panels that don't oil can. So if he is saying that he can't guarantee the integrity of the work as in leaks, he probably doesn't understand oil canning.' Carefully read the waiver to see if it is just saying it may oil can, or if it is saying that it may underperform / leak / lose structural integrity.
Nate Libbey
5/20/2010
Gayla, Striations greatly reduce the chance of oil canning (ripples) in the panel by strengthing it between the ribs. Also when the panel expands and contracts in heat and cold, they take up some of the slack.
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