Standing Seam good choice for low slope roof?

Guest User
7/18/2005
I have an addition that has a roof with a slope of 1.2:12 and am trying to find a good roofing option for this part of the house. A contractor has proposed asphalt shingles (which are not approved for this slope), a special low slope system that looks like a big sheet of contact paper and costs a heck of a lot, or a standing seam metal roof made of steel with a 70% Kynar 500 coating which costs even more than the contact paper. Using metal just for the addition (which is about 1/4 of the roof) increases the total cost of the job by 50%. I'm trying to figure out if it's worth shelling out for the metal How long can I expect this metal roof to last? I have a lot of trees in my area. I try to keep them trimmed back but small branches are always falling on the roof. Will a metal roof be easily damaged by falling debris from the trees? Will installing a white metal roof to replace the existing light colored asphalt shingles make this room (which has no attic) cooler in the summer? Will it make it cooler in the winter? Is there anything to look out for in this situation? (I do have an inquiry in with the manufacturer of the roofing material.)
Todd Miller
Classic Products, Inc.
7/19/2005
First of all, if you choose standing seam, make certain that the product being installed is approved for this low pitch. Not all standing seam roofs are appropriate for that low of pitch. You will probably end up using a "double lock" or "field-seamed" mechanically seamed panel. Also, make certain that the product is being installed properly as far as substrate it is going over, underlayment, attic ventilation, etc. As far as damage from falling tree limbs ... metal roofing is pretty tough ... you may wish to seek a heavier gauge product. However, all types of roofing can be damaged by tree limbs. Metal is more resistant to damage than most products are and, if metal is damaged, it is often only cosmetic damage. I hope that your attic has insulation. I wish that it had the 1" ventilated airspace required by code. A lighter color roof, or one which utilizes heat reflective pigments in a darker color, will keep the building cooler in summer. It really will not have much, if any effect in winter. I am glad to hear that you are contacting the manufacturer of the roofing. Ask if they are members of Metal Roofing Alliance and Metal Construction Association (MCA). Ask also if their products meet the quality requirements of the MCA Certified Metal Roofing Panel program.
Guest User
7/19/2005
Is there some other type of metal roof that would be appropriate for a 1.2:12 pitch? I got the impression that most other products are like metal shingles and would require a higher pitch. What does "double lock" and "field seam" mean? What are the alternative seam types that are probably not suitable for a low slope? I understand that all types of roofing can be damaged by tree limbs, but if I install something with a ten year lifespan and I have to replace it that's less of a loss than something that is supposed to last 50 years and came with a correspondingly high price tag. I don't really care about appearance. This roof is in the back and because it's low slope and there are no hills, you can't really see it from the ground. It seems to me that the weak point with falling tree limbs would be damage to the Kynar paint which would then open the door to rust. Is this a possibility? How do you repair damage to a metal roof? Do you call it an attic when it's a 6 inch space between the roof decking and the drywall ceiling? I believe that it is insulated but I have no clue if they left a ventilation space. There is a soffit vent. Is ventilation particularly important with a metal roof? My main attic has poor ventilation, something I hope to correct with this reroofing by means of a ridge vent. Ventilation seems to be a tricky matter. Roofers don't seem to take it very seriously. I read that you're supposed to have a balanced air flow with as much ventilation at the bottom as at the ridge but I have a roofer who really takes ventilation seriously (for a roofer) telling me that it's good enough to install a ridge vent (NFA 18 in^2/ft) at the top and two inch circular vents every four feet in the soffit (NFA 1 in^2/ft at best, probably much less). (I guess I should note for people reading this that NFA=Net Free Area. It is the open space for air flow provided by a ventilation product.) The roofing material company is Englert. They do appear listed on this site so I assume that means they belong to the Metal Roofing Alliance. They are sure taking their time answering my email, however.
Todd Miller
Classic Products, Inc.
7/19/2005
Thanks for your response. The main risk with metal roofing and tree branches is aesthetics. Most metal roofing products have passed the UL 2218 Impact Resistance test at its highest level, Class IV. As a result, insurance companies in hail-prone areas offer discounts for owners of these roofs. In most cases, repairing a metal roof will involve replacing damaged panels. Most systems can be "opened up" to do this in a limited area if necessary. In other cases, multiple panels may need to be removed and re-installed. Most of the shingle-style metal roofs require a 3:12 pitch. There may be some standing seams with a single lock or snap lock which can be installed at 1.5:12 but I would feel more comfortable with a mechanically seamed panel which means the seam is actually crimped closed with a seaming machine. As far as ventilation, I would work to get your intake and exhaust balanced or, if anything, have more exhuast than intake. I hope this helps.
Guest User
7/19/2005
Thanks for your reply. I have heard that having excess exhaust ventilation can lead to air being sucked out of the living space in your house, at least when the house isn't air tight. (My house is 50 years old and certainly not tight.) This is supposed to be a particular issue with powered attic fans. In any case, I am doing my best to get a balanced system, in spite of the roofers. I would think that replacing a section of the standing seam roof would be a major undertaking since you'd have to disconnect it from the roof above, and it would be a pretty large section---not like the metal shingles. What sort of life span can I expect out of a Kynar coated standing seam steel roof (assuming no catastrophes). I'm not near the ocean, so no salt to worry about. I assume that eventually it will rust?
Todd Miller
Classic Products, Inc.
7/19/2005
With today's quality Kynars, you should be able to expect a minimum of 40 years out of a quality steel standing seam in a non-coastal environment. As you mentioned earlier, you may need to watch for scratches and touch them up if they occur. However, these finishes are pretty resistant to scratches from things like tree limbs. You could also consider aluminum or even copper as other options. I do not know a lot about your roof configuration to say about replacement of individual panels. With a field-seamed panel, though, yes, you may have to start at the finished end and remove panels back to the damaged area.
Guest User
7/20/2005
Wow, if you have to start at one side and work back to the damaged area that essentially means that this roofing can only be replaced, not repaired. I know copper is reputed to last a very long time but it is also said to carry a very high price tag. And I'm still struggling to decide if it's worth paying the price (50% more for total job) to have metal on just 1/4 of the roof. Does aluminum have a longer lifespan than Kynar coated steel?
Todd Miller
Classic Products, Inc.
7/20/2005
Kynar-coated steel will eventually have to be re-painted to keep it durable and corrosion resistant. Aluminum, on the other hand, would not "have" to have that done.
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