Metal roof types?
SLCtinman
| Posted in General Questions on
I am a residential designer with a client who wishes to have a metal roof. The question is what are the pros and cons of standing seam metal roofs vs other, less expensive types?
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Replies
Timothy,
Standing-seam roofs have concealed fasteners. To many eyes, this improves the appearance of the roof.
Some people believe that a standing-seam roof will last longer than a through-fastened roof, but I don't believe there is any universal rule that holds here. The answer is, "It depends." A well installed, well detailed through-fastened metal roof will last for decades -- certainly longer than a poorly installed standing-seam roof.
I have read about moisture condensing undeneath ribbed roofing and causing prob;ems, if you search fine homebuilding you might come up with something on that. Also ribbed roofing is harder to detail around dormers and skylights.
Thanks for the replies! Primarily I am finding the primary difference (besides price!) is indeed aesthetics...as for Mr Goodwin's comment about harder to detail, how much harder? moderately harder, alot harder? I think the key is as Mr Holladay said (and this applies to alot of items in the construction field) "a well-installed, well-detailed..."
• Apart from the visible fastenings, ridge and hip flashing details on a ribbed roof tend to be chunkier and more prominent.
• For ribbed roofing I'd recommend Master-rib rather than the traditional 5V (also known around here as farm tin). Crisper look, no oil-canning, probably more weather-tight.
• ribbed can be installed over 1 x 3 purlins if you wish, standing seam generally requires continuous sheathing.
• detailing is easy! Just don't try and do it yourself - hire a roofer with abundant experience and an established reputation in the material and learn to trust them.
• As a designer the most important thing you need to know is that with any metal roofing, complexity quickly drives up costs. simple gable roofs with minimal penetrations are best and most cost-effective for this medium.
A lot of what is called "standing seam" metal is more properly called "snap-lock". It is blind fastened and then snaps together at the overlapping ribs, one panel at a time. Traditional standing seam doesn't snap together, it is seamed together in place using special tools. This method would probably be used if you hired a coppersmith to make and install copper panels.
Snap-lock is extremely common around here, and a 24-gauge (preferable to me) or 26-gauge panel will last many decades. One of the keys is the paint system used--you need to read up on the differences in paints and choose accordingly. We use products from Champion Metal, Nu-Ray, ASC, and a few others in this market.
I have seen condensation issues under metal roofs, but only in situations where the slope if very low and where there is no solid deck or felt installed under the meta. A client of mine had two carports with 1:12 exposed fasteners roofing over purlins, no felt, and it dripped from the underside. Another client of mine has a large metal building with a 1:12 snap-lock roof with fiberglass metal building insulation (4-6 feet wide with a vinyl sheet underneath it). That one condenses and the water collects in the insulation until it drips out. I have never seen any issue like this with a roof that's at least 3:12 (most manufacturers spec this) and has felt under it. My guess is that a little bit does condense, but it runs down the back and out.
Thanks again to all. To the comment by Mr Morgan re simplicity I couldnt agree more. Having spent 14 yrs as a skilled tradesman (sheet metal at a GM factory) plus three years on a framing crew, I saw first-hand unrealistic or unduly complicated designs - so a major emphasis of my design credo is simplicity. While certainly beautiful (to some) these houses with 6 different slopes, turrets, gables, hips, etc ALL IN ONE HOUSE just dont make sense to me. I believe one can attain beauty, architectural interest, varied ceiling heights, etc etc without undo complexity. The house in question is a 2800 sf single story hip roof w 4/12 slope thruout, two gable-end projections and one dormer. The client has an existing metal bldg airplane hangar on their property with a raised rib metal roof by MBCI and wish to match that look (or close to it) on their new house. They were going to simply use the same product until a bidding contractor said they should go with standing seam because it was FAR superior, so I was tasked to find out how true this statement was....thanks again to all who replied, very helpful!
by the way, the house is to be located in southeastern Utah in a high desert climate (both 100 degree summer days and cold winters with average temps below freezing) ...
As good as those factory paints are, I'm seeing fading in sunny environments like here in Colorado.
I realize you have to match the other building.
For everyone else, I'd say go with the silver galvalume finish. Never seen a problem with that anywhere.