I strongly discourage my clients from using any system of metal roofing that is not a "hidden clipsdown" system like traditional standing seam or similar system. I just removed another metal roof last week off a barn we deconstructed for reuse. It had a beautiful hewn timber frame from the 1820's, but the current client thought it was a good idea to take of the old rusted "standing seam" roof off (that was not leaking - just unsightly from their perspective) and replace it with a "screw down" metal roof. The grommets only lasted ten years, and the roof started to leak, leading to water damage to the rafter plate and some rafters.
It never struck me as logical to cover a roof in solid sheets of metal (a good roofing material) then put hundreds of holes into each panel thinking it would not eventually leak. The grommets have a very limited service life. Yes you can find some that are better that other, with a guaranteed service life of 25 years (and you pay for them) but it is not a matter if they will where out, but when. When they do fail, you may not know it right a way and only discover it after there is damage to the roofing structure itself. Assuming that you discover the leaks quickly, you still have to go up and take the old screws/nails out and replace them with new ones. Just a waste of time, and a risk not worth taking.
As a special note, in 35 years of working in and around the architectural field, I have never seen a warranty for gourmeted fasteners that fail honored by a roofing company or manufacture, which renders such guarantees worthless.
Buy your metal where it will be long enough to overhang as much as you think right, on my regular roof it overhangs past the walls about 2', make sure your rafters extend on the edges of the house too, as the metal needs be sturdy supported in those areas. Sturdy enough to hold a man standing on it. Short seam screws come in handy at the bottom edge in addition to whatever rafter support you have. Rain will still splash against the house walls or foundation. So make sure your house below the roof is moisture proof in that area also where the rain might splash, use metal there if you want, or gutters might be a huge improvement. Not sure about your A-frame set-up, but doorways and windows also need a large overhang to prevent rain/splash, especially if there an entryway stair or stoop (a concrete stoop splashes rain on a doorway or wall like crazy).
I would use the best (heavy) asphalt tar paper you can find, it must be water tight & any seams or holes or staples should be sealed with roofing tar, don't buy old or damaged rolls unless you want to make extra work for yourself. Overlap each strip of tar paper well & use roofing tar to glue it to the next strip, the overlap is such that the water will always shed on top of the paper. (lay the first strip of paper at the bottom of the roof, then overlap each strip as you go up the roof, hope that makes sense) I really recommend the tar paper, as metal roof is guaranteed to condensate moisture on the underside whether the house is heated or not, a simple light frost being melted by the sunshine will cause the metal roof to literally 'rain inside the house'. If you can imagine a foot of snow on the thing, and a nice warm house, or even very cold...it will condensate on the metal underside, this is why I recommend the heavy tar paper & seal well with roofing tar.
When trying to get your roof on straight, try the first piece at one end, and another piece of metal at the other end, scribe bright lines (with a chalk line) across the top & bottom for the roof span, IF all your metal is the same length then it should come out pretty good. It is worth the extra effort to make & set a 'runner board' along the bottom of the roof, that runs straight & square at the bottom edge line, get that set right and the metal install is simply set, sheets against the runner board to help hold the sheet as you neatly position the seams all the way to the ridge. There is a little 'wander or variance' that will happen while setting the seams together, so the runner board helps keep things square looking at least at the overhang edge. Your metal sheets need not butt at the ridge line to the other side sheets, nor be perfectly straight like at the bottom edge, because you will have a fine ridge cap to cover that gap, so if some sheets are shorter than others, it shouldn't matter much. Just try not to get 'off square'. Make sure your ridge line is completely sealed/capped with tar paper & roofing tar before the metal install. There is a thick gasket material that is made to fit your style of metal roofing, those strips fill the void between the ribs/flats of the sheet metal and the ridge cap, use those if possible, & use roofing tar too make them permanent in place. You can also find a gasket that fits on the underside of the metal sheet, it locates at the bottom edge of the roof & seals out dirt & wind, but I left those out so that all the condensate on the underside could drain out.
I've only put on two metal roofs, ~~~so take everything I suggest with a huge dose of salt!~~~ LOL
This should get you going in your vetting contractors and/or suppliers. You can do the work yourself and there are companies that will, "cut and drop" pans for you as it is called in the industry. Check in with us here with your progression, and/or needs.
I appreciate your concern, but your comparisons are a little inaccurate. For one thing, you can't use bricks for roofing, and it is no more or less natural than metal is so I will assume you meant clay tile which is a wonderful medium but in most markets much more expensive for folks than metal, and require extensive expensive shipping. As for a carbon footprint metal has one of the lowest because it can last so much longer than other roofing mediums, and is much easier per square foot of coverage to manufacture and ship than just about any other roofing material, making it one of the most ecologically sound roofing materials you could use. Wood is also good, yet comes with it's own issues, and limitations.
As for LEEDs, I am involved in several discussion groups that are confronting LEED for it "whitewashing" of green standards so "industrial products" and corporate sponsors take precedent over true and actual "natural and traditional building practices." LEED started with good intentions but has slowly devolved into a mechanism for the mainstream construction industry and corporations to try and influence and change what they think "green" standards are to be. I could, (and have been) challenged that this is a subjective opinion, yet I have not seen a, "natural or traditional" built home yet receive even the lowest LEED rating, and the gap is only getting larger. Now we are also faced with a potential monopoly as LEED is becoming mandatory in some area. This is actually much worse than general building Code, as LEED is but one standard, and true green architecture needs room to include other interpretations.
Al Turner wrote:Jay, I did a search for metal roofing hidden clipsdown and did not have any luck in finding what you were describing. I am not sure what I should be seeing so I may have seen it but with a different name or description. Can you maybe post a few links to some manufactures that make this kind of roofing? I'm in Arizona so one or two in the West would be helpful.
In the States, it's called "hidden fastener" vs. "exposed fastener."
I put one on my own house this summer.
Jay C. White Cloud wrote:As for a carbon footprint metal has one of the lowest because it can last so much longer than other roofing mediums, and is much easier per square foot of coverage to manufacture and ship than just about any other roofing material, making it one of the most ecologically sound roofing materials you could use.
Yes! And what's more, it's maintainable. The off-the-shelf lifespan is excellent, but when you consider that it's perfectly possible to re-coat the metal when the initial coating deteriorates, then you're looking at a really magnificent service life. When your wood shakes deteriorate, what can you do? Same with clay tiles, and (much sooner) your asphalt shingles. When they wear out, you have to throw them away and install new ones. When your metal roof wears out, you repaint it. And if you like, you can repaint and repaint and repaint it for a very very long time. (As coating technologies are improving, the intervals are increasing, too.)