Has anyone out there had any experience with installing exposed-fastener metal roofing on an SIP roof? I have a shed roof that consists of 4 – 24′ x 8′ SIPs side-by-side with a 2′ framed overhang added on for a total size of 24′ x 34′.
I propose to install 34′ metal roofing, with ice-and-water shield underneath, screwed into the 2 x 10 splines that hold the adjacent panels together. Roof is sized for local snow load, and it’s in Upstate New York where we don’t get hurricanes and tornados.
Two questions are:
Will the roof stay on if its fastened at 8′ centers? It’s plenty rigid, 24 gauge, and the deck is continuous. Rakes and eaves will be factory metal trim. Glue it to the ice and water between the 8-foot centers?
What about this type of “hot” roof? Will roofing channels provide enough ventilation to relieve heat buildup and possible condensation?
Thanks, Nick
Replies
>>>>>>>>>>>>>Will the roof stay on if its fastened at 8' centers? It's plenty rigid, 24 gauge, and the deck is continuous. Rakes and eaves will be factory metal trim. Glue it to the ice and water between the 8-foot centers?
I'd guess it wouldn't unless you live in an area with absolutely no wind.
>>>>>>>>>>Glue it to the ice and water between the 8-foot centers?
Why don't you turn the I&WS upside down and stick the roof to it? You better rethink this whole project. Good Luck.
"Let's go to Memphis in the meantime, baby" - John Hiatt.
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Why aren't you attaching it to the osb between the splines?
Tom
Douglasville, GA
Hello to TomW. Thanks for the reply.
I don't think there's a whole lot of holding power for roof screws in 7/16" OSB, especially when the screws have to compress the neoprene washers, but a little is better than none at all, I guess, especially when the screws in the 2x10 splines between panels at 8' OC are doing most of the work.
I'm trying to find a valid way to not add sleepers and purlins onto this roof if it's not necessary. My gut tells me the metal roofing only needs minimal fastening to stay in place on top of the SIPs due to the flatness of the roof, gravity, and the fact that wind can't get under the metal. People with OSB experinnce have said "just screw the metal down" but I'm looking all the experience I can tap into.
I think that the screws will have plenty of holding power in 7/16" osb. Individually, it may not be much, but at ~1/square foot, it will be plenty. Spreading the screws out as much as you say is not a good idea. It may work fine for a long time, or you could easily get the freak windstorm that takes every peice of metal off your roof. Don't build it for the average day, build it for the extreme.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
I put a metal roof on my SIP house in NH and there is plenty of holding power in that OSB. There is no way I would consider only attaching it every 8 ft.Tom
Douglasville, GA
i just want to point out nick, that here in southeastern north carolina (hurricane country) there are lots of roofs that are fastened directly to the osb sheathing that covers the rafters/trusses.
now that sheathing is usually 1/2", and the fasteners may on occasion actually be screwed into a rafter/truss, but let me assure you that no attempt is made by the crew installing exposed fastener metal roofing to hit anything but the sheathing.
i know for certain this is the standard practice. can it be improved on, yes but exposed fastener metal roofing installed in this way holds better in hurricanes than any other standard system.
I was a little flippant in my first response - Sorry. The way your roof needs to be installed, regardless of on sips or not, is to the manufacturer's instructions. There's going to be some sort of expansion/contraction to the metal, so glueing is not an option. Read the installation manual.
"Let's go to Memphis in the meantime, baby" - John Hiatt.
http://grantlogan.net/
Hi
I appreciate a frank reply. I didn't hear exactly what I wanted to hear, but I appreciate your directness. I might have responded in a similar fashion. I work in construction, as a project supervisor on public works, and usually the first words out of my mouth are "did you read the Spec book and the contract documents?"
Unfortunately for me, the manufacturer's (McElroy Metal) information is pretty vague and they're non-responsive when you send them inquiries for technical assistance. I think they ignore you until you give up or consult your own engineer. The supplier/lumberyard I buy from doesn't get any better response from McElroy than I do. So, I'm relying on the experience of folks who have had experience in the area where I'm a little unsure of myself.
So far, the replies seem to indicate that there's a good possibility that metal roofing can be applied with some improvements to my proposed method.
These Fine Homebuilding forums are a wonderful thing, and I hope to become a more active participant.
Nick in NY
check out metals sales .com. i have used thier propanel 2 look at the intrsuctions for that product to get started larry
hand me the chainsaw, i need to trim the casing just a hair.
Metal roofing is pretty much a commodity: Roofing suppliers, and some installers, have the dies and machines to roll the patterns and cut them to length. ( There are a couple of local outfits here who roll and cut the roofing to spec on site).
The primary difference between them is the quality and thickness of of coil stock they purchase and use, which varies in quality of galvanizing and coatings.
Metal roofing "manufacture" is little different than the "manufacture" of continuous gutters.
What is pretty consistent between the various types of roofing, whether it be hi-rib agricultural style roofing, standing seam, or whatever, is the fastener specs and fastener spacing.
What can distinguish one supplier from another, is the patterns of their flashings, but the various metal roof suppliers I've dealt with over the years provide pretty clear instructions for attaching their product to various roof structures and shapes.
HOWEVER, some suppliers are less customer oriented than others, so, when facing a dilemma such as yours, I would probably call around some of the other suppliers and try to get your hands on some of their spec sheets.
I doubt those specs/instructions will vary much at all.
any comments on the condensation Q at the end of the beginning of the thread?
If the roofing is layed directly onto the sheathing (over an underlayment) there will not be a condensation issue.
Metal roofing over purlins without blanket insulation or an underlayment will create mini-rainstorms inside the building. (A situation sometimes seen in polebarn-type construction).
Metal roofing over purlins without blanket insulation or an underlayment
Shouldn't be a problem for OP over SIPs. Having been in such 'rain' before <g>.Occupational hazard of my occupation not being around (sorry Bubba)
The metal roofing will be hotter than the surrounding air, so condensation won't be a problem. Your SIPs are a great moisture barrier as long as they're foamed together and detailed well, and they're also a great insulation.
Condensation is a problem when warm, moist air from inside can make it to the metal when the temperature of the outside and the metal are lower than the dewpoint of the inside air. You'll not have the inside air getting out there. When outside air finds it's way under the metal roofing, it will usually heat up (because of the solar radiation hitting the metal roof).
You'll be fine.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
Zak, I agree if they only work during the day, but if moisture has migrated up thru the SIP's and nighttime rolls around when the outside air temperature is below the inside air dewpoint, condensation will occur. Hence the need for the airspace as well as the eave and ridge ventilation.
if moisture has migrated up thru the SIP's and nighttime rolls around when the outside air temperature is below the inside air dewpoint, condensation will occur
Moisture won't migrate up through the SIPs- that's probably 10" of foam, and two layers of OSB, foamed together at all edges. That's one of the beautiful things about SIPs- the condensation point is inside the foam, and air and moisture can't get to that point.
Unless, of course, the SIPs aren't put together right. Which happens, like with the alaska SIP problems.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
with SIPs, condensation should not be an issue
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My turn...I have installed more McElroy Metal than any other. They have a lot of tecch sheets available. I used to get them through the retailer I bought from and have seen them online since. Time to sharpen your googling skills, unless for some lliability reason they have pulled the PDFs but I find that hard to believe. almost any and every product made in this country has tech data available online as PDFs.In general, a good rule of thumb is that you need a pattern that gives you about one fastener per foot. I use the larger diameter fasteners with the 5/16" head. They displace a lot more wood and get a better grip. In colorado I had seen a few roofs where the smaller sized screws snapped heads and the metal came off. There could be several reasons for that. I was not the installer, so it could have beeen installed with a driull instead of a clutched tex driver and run in too tight to begin with. It could be that the length of the metal created too much expansion from thermal growth and that is what sheaared them off, or it could be that the ice load was too punisshing at that elevation in the mountains. I don't know, it's even possible that some hack used a hammer to install them, LOLAnyway, you would be sorely disappointed with your roof if you installed it as you mentioned in your first post. Even if wind were never a factor, the thermal expansion alone would give you some interesting wrinkles to look at.I am also interested in what pitch your roof is to be. I am not used to seeing or hearing of I&W shield in this placement unless for a pitch les than 2/12. Is that something that is allowed by the SIP manufaturer? Be wise to check with them and your total HVAC design and system.
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http://www.mcelroymetal.com/content/products/display.cfm?product_id=19there you go. Load, span, fastener schedule will vary according to pitch, style of metal, gaauge, etc, but it's all right in these pdfs
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One thing about wind forces that I think is often overlooked is the vacuum high winds can create on the back, or lee side, of a structure.
Here in my coastal climes, I often see the shingles pulled off that back side, especially the cheap 3 tabs on spec homes built in the 70's and 80's that were stapled down rather than nailed. And in a storm, you can often see the lower edges of the shingles pulled up and fluttering in the breeze.
It's not just uplift that tears up roofs.
The most extreme case I ever witnessed was on the lee side of a house I built several years ago on a high bluff above the sea, an empty refridge behind the house was picked up and flung over 100' feet before landing in some trees.
Right you are. Most of the wind removed shingles I've had to replace were on the lee side, about two feet down from the ridge.
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Which is why, in hurricane country, you are much more likely to first have a window sucked out of an opening, and near a corner, than blown in.
Full scale wind tests in the product testing labs always go at least fifty percent higher on the negative side.
Hi
I've been away from the computer for a couple of days. Thanks to everyone who has added input to this quest for information. I copied the posts I'm responding to below.
Some further description of the application I'm putting metal roofing on:
As described before, it's a shed roof, 24' x 34', 10" Insulspan panels with 2 x 10 lumber splines, tight fit and detailed properly. The roof pitch is 1-1/2 on 12. The ice and water shield on the SIPs was applied as a temporary roof/underlayment layer for whatever the roof turned out to be. I'm a first-time builder and the final result will be my home. Working mostly alone and holding down a full-time job has made building this house a challenging project. I always say to my friends that 100,000 Egyptians could build a pyramid in a year, but this pyramid will take me 100,0000 years to finish. Guess it's the journey, not the destination, though at 60 building this "final resting place" has some urgency.
The underside of the SIPs will have an additional 2-1/2" of isocyanurate board insulation applied, since I bought a truckload of it really cheap and this seems like a good place to use it. Total R of the roof should approach 60. House will have an air exchanger, and I don't think vapor transfer through the roof will be a problem, since there won't be much vapor to get to the roof, iso panels should be the first line of condensation if there is any, and the SIPs are completely caulked and made impermeable on top by the ice and water shield, so there should be almost no vapor drive available to make vapor pass through to the underside of the roof.
I read the accounts of the Juneau roofs and responded the best I could with what I had available.
As for fasteners, I plan to predrill all holes in the metal roofing, and I guess I'll do some "test holes" with 1/4" and 5/16" screws and scrap pieces of SIP and metal roofing. I have a real screw gun so QC on screw installation torque should be OK.
Maybe I'm being a little harsh with McElroy, but they don't make a human available to answer questions from folks like me. Maybe my questions are so novice that they'd rather use their resources to deal with bigger accounts than an owner/builder, but, to borrow from the Beatles, I'll get by with a little help from my friends...
Thanks again to all
Nick
Moisture won't migrate up through the SIPs- that's probably 10" of foam, and two layers of OSB, foamed together at all edges. That's one of the beautiful things about SIPs- the condensation point is inside the foam, and air and moisture can't get to that point.
Unless, of course, the SIPs aren't put together right. Which happens, like with the alaska SIP problems.
zak
In general, a good rule of thumb is that you need a pattern that gives you about one fastener per foot. I use the larger diameter fasteners with the 5/16" head. Anyway, you would be sorely disappointed with your roof if you installed it as you mentioned in your first post. Even if wind were never a factor, the thermal expansion alone would give you some interesting wrinkles to look at.
I am also interested in what pitch your roof is to be. I am not used to seeing or hearing of I&W shield in this placement unless for a pitch les than 2/12. Is that something that is allowed by the SIP manufaturer? Be wise to check with them and your total HVAC design and system.
piffin
you'll want a butyl tape (rope caulk ) on the seams at that low pitch, or another quality flexable caulk.with good detailing and the exchanger, you should be fine.also, one of the most common mistakes I see novices make is to put the female lap on top. Be sure you know the right way to lap it. I have drawing on other PC if you have any question
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Hi
Thanks for the tips for dealing with metal roof application. I've done three metal roofs, but they were all conventional metal-over-purlin, steep-pitch jobs; hence my apprehension with a metal-over-SIP-deck application. I'm familiar with the one-way lap arrangement.
I'll be using the caulking tape McElroy supplies; I've used it for all sorts of sealing applications. The stuff I put on 10 years ago is still sticky; it's pretty amazing.
So, I'm off to the races. I'm sure I'll be tapping into this wonderful source of experience many more times before this castle is built, and hopefully I'll have something to contribute.
so much talk here about how to lap,i thought i knew,but i'm questioning it after having some trouble with the laps laying flat . the metal i'm using now,on one edge as the rib turns down it is cleancut.the other edge turns down then makes about a 1/8 turn to flatten out. is that clear?lol i'm not sure which one you would call male/female. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
The one that turns back out an eight to lay on the supporting roof sheathing goes down first - the female lap. She has a divot along one side of that rib also. This is so that any water that might be getting forced or wiccked up under the male edge will have a way to run on down rather than up over to leak.The male lap edge is the one that doesn't quite lay all the way down to the same plane that the majority of the pans do.
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i had to do a little research,i have done 5 buildings in metal sales -pro panel 2. so i'm thinking how stupid can i be,i've installed it all wrong. but checked their tech page. on pro panel it would be really hard to do wrong,so i can relax on previous jobs but........ on the brand i'm using now i have put up the sides wrong i have the one with the tail on top.i'm going to leave the sides ,but i'm sure glad to catch this before i'm on the roof. do you think on a 3/12 roof i need the tape on the seams? manf. doesn't say anything about it. thanks,you saved my rear just in time before the roof goes on. larryhand me the chainsaw, i need to trim the casing just a hair.
Tape for 2/12 and less, but if you anticipate ice damns, i'd consider it.
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Check out http://www.buildingscience.com for more guidance. From what I can determine along with the roofing manufacturers, you want to be able to have the roof assembly transfer the moisture thru the SIP's to the surrounding air since their permance is about 1. Also, the SIP manufacturers tell you to install 2 x sleepers, and then the roofing.