This is for review for thoise who do metal roofs. I’m very interested in comments from those who have installed plenty or who have done call-back work on them.
Not flat pan standing seam or fine copper pnals, no, I’m talking about the more common (vulgate version) ribbed panels that are fastened down with Tech screws.
Have you seen the screws loosen up and do you have a theory why?
When I was in Colorado, I installed miles of the stuff and naver heard a complaint on my work in the twelve years I was there. the very first couple ones that I did were fastened with the smaller screws that the companies recomend – about a #8 or 10 shank with a 1/4″ hex head holding the cup washer and neoprene gasket down to the steel.
I wasn’t too impressed with the small shank size and switched to using the heavier ones with the 5/16″ head and at least twice the displacement ( read holding torque) of wood from the larger shank size and thread surface. Along about that same time, I was called to replace and refasten a couple of panels on a nearby roof that had been installed with the smaller screws – by another roofer.
On that roof, it was clear that he had over-torqued the screws because the gaskets were terribly disformed and split and many of the heads were snapped right off. This was in the early days of metal roofing of this styule so I presume that he had merely used a drill to set them instead of a clutch drive tec-screw driver.
Anyways – I always used the larger tec-screwsafter my first couple roofs and never heard of any problem.
When I moved here and built my own house, I ordered the metal roof package and it showed up with the smaller shank screws. Being in a hurry to get under cover, I went ahead and used them.
Guess what? That was a mistake.
A couple weeks ago, I was up adjusting the satellite dish and looked out across that field of green ripples to see several screws standing proud. WE’d had a minor leak that I assumed was from around a skylight ( they are a bugger to seal tight in this kind of roofing) but I guess it was from loose screws.
Today, I got out the chicken ladder onto the ridge and re-fastened the whole darn thing with the full size fasteners.
I have heard someone once theorize that thermal expansion can cause fasteners to loosen but never explain how. I am also interseted in hearing from others if they see the same thing that I do – the larger screws have more than enough holding power to resist pullout or loosening????
I could have other mitigating factors here. The slats I fastened to were rough cut 1x slabbed out green here three months before construction. There may have been some shrinkage in that substrate to account for part of the prblem. Have you all noticed any difference in holding power between plywood and solid lumber for fastening?????
I want to understand all the possible dynamics I can in this.
Comments anyone?
Excellence is its own reward!
Replies
Piffin- I don't have any answers except I've noticed screws backing out on every one of these type roofs I've ever been on. I think all the one's I've seen were installed on purlins. I can't remember any plywood. Good Question.
About 12 years ago we built a house with a sheetmetal roof of this style, one roof plane was over 40 feet long and the other was only about 20 feet in length, It was installed over plywood and the screws on the long side of the roof ended up backing themselves out a bit over a period of 7 or 8 years, but the ones on the short side of the roof were fine. I chalked this up to thermal expansion and torqued the screws down again and haven't had another call from the homeowner, though I'm sure they continue to back themselves out slowly. Come to think of it, the worst screws were near the ends of the sheets, which would reinforce that it was thermal expansion that caused this.
My own roof was done about 6-7 years ago and the panels are about 20' long but there is not consistency to which of the screws are backing out worst. If anything, I would have to say that it was the ones in the third row up from bottom, say six feet up.
Were your screws the ones with 1/4" heads and smaller shanks? These seem to be the ones reommended by the manufacturers, but I can't see why.
Another thing I have always done is to predrill the screw holes slightly oversized to relieve this sort of thermal tension..
Excellence is its own reward!
These screws were larger, if i remember.....3/8 heads. The roof was 1/2" plywood. Have you found predrilling helps? I don't try to make a habit of doing sheetmetal roofs considering the amount of snow we get here, it can become dangerous.
My main reason for using the larger pre-drilled holes is this - I can stack all the sheets on the ground evenly and drill them all at once. it is pretty hard to get a screw to self start in that steel when you are hanging onto a chicken ladder on an icy 9/12 roof. This increases safety and helps speed things up, but the real beauty is that all the screws line up neatly instead of meandering along like a litter of puppies just out of the kennel..
Excellence is its own reward!
all the screws line up neatly instead of meandering along like a litter of puppies just out of the kennel.
HEY! You didn't say you'd looked at any of the roofs I did.Any jackass can kick down a barn, but it takes a carpenter to build one.
I haven't done a lot of pole buildings - Maybe 10 at the most. But honestly, I've never had a problem with the 1/4" head screws backing out or breaking. Not a single screw that I know of.
Don't know if it makes a difference but I've always put the screws in the ribs, not the flat spots. And I usually use 2.5" screws.
Unfortunately, I've only gotten paid for building ONE of the ten or so. All the rest were freebies for non-profit groups or relatives.I've been thinking about a sex change. Specifically, I could start having some.
Putting them in the ribs is a holdover from the old days of lead headed nails and corrugated roofing tin, but there are a half dozen reasons not to do it with this ribbed panel type of roofing - but that's mostly another subject.
You do bring focus on the screw length though. Mine that were pulling out were 1" put into 1" lumber.
As with nails, the holding strength is a function of displacement. The more wood that is displaced in setting the screw or nail, the more holding ability it has. So a #10 screw that is 2" long has twice the hold that a 1" screw has. Likewise, the larger shank diameter I used to replace mine with, have now displaced a larger volumn of wood so hopefully I won't be up there using the screw guns again in a couple more years..
Excellence is its own reward!
The few ribed steel roofs I've installed, we put the screws in the ribs. This is what the guys I was working with/for wanted. Seemed to make sense to me. I would like to know the reasons that it should not be done.
Thanks for your input,
Shoe
Screws in the ribs - this is one I explain about every six months here. I'll have to save this explanation to avoid typing it again in another couple months.
first - don't do something because the other guys do it. Remember what your mother said about jumping off a cliff just because all the other kids....See if those other guys have read the directions from the manufacturer first. A lot of installers have never done so and a lot of them even intall the laps backasswards with the female side on top where it encourages leaks, especially on lower slope roofs or when ice builds up.
Think about the fact that the very idea of a screw fastened roof fights against the basic rules of roofing. In order to hold my roof down, I have nearly 2000 little holes poked in my waterproof membrane.
Hmmmmmm....
So to stop water from geting into those holes, a carefully shaped cup washer holds a neoprene gasket in compression against the steel. Get it in crooked and you have a potential leak. Secure it too tightly and you have a potential leak from having fractured the gasket with overtorquing it. Let the screw set too loosely, and again, you have a potential leak when water can seep in or wick in under the gasket. A loosely set screw can also let ice grab at it and do damage.
So if you are setting the screws on the flat, with the wood tight on the other side of the roof metal, you can control the seating of that gasket to be just right. ( aside - this may have been a part of my trouble, having used green lumber that was rough cut and not planned. The shrinkage from green size to dry and the furriness of rough saw kerfing may have prevented me from having a good tight fit without knowing it)
But if you set the screws on the ridges, there are a number of things that can happen to prevent optimum torque-down and seating of the gaskets. The rib can be drawn into the decking - or purlin - and deform the panels variously. As this happens, if the rib is too tightly set, the flat panel is buckled up into a convex shape like an airplane wing. Wind blowing over this will create additional uplift so the whole surface is doing extra rippling in a windstorm. That extra uplift requires still more fasteners to prevent it from being torn off. Also, as the metal skin is rippling, the seating of the gaskets is constantly being challenged. The reasoning goes that this can be overcome by being careful not to over tighten those screws in the ribs. True enough, and you do gain something by the fact that less water is running on the ribs than in the pans to find a way in when you do have a loose screw, but still, the wind can gain more uplift on unfastened flat pans than on tightly fastened ones. If I were to be required to install with fasteners on the ribs instead on on the pans, I would be looking for at least a 24 GA metal. residences are more commonly done with 26 to 29 GA metal. I believe that mine is 28 GA
In commercial steel buildings where the skin is also a part of the structural engineering, it is even heavier gauge yet, and the fasteners go in the pans for solid connection.
Part of the intended design of the ribs is to absorb the thermal expansion laterally instead of longitudinally and still maintain a profile without letting the whole skin look wrinkled like you fingertips after a long time in the water. Fasten those ribs too tight, and you interfere with that intended design aspect and froce the expansion into the pans for more uplift.
So you find that most manufacturers recommend the screws in the flats.
Another less important reasson is that when you place them in the flats near the break to the rib, they become nearly invisible from most viewing angles to let it simulate the appearance of a better roof a little better. The screws hide in the shadow lines.
Another metal roof skin called MetTile is stamped out to look like Spanish barrel tile. It has very little contact point with the decking under it and it is designed to be fastened in that location which also happens to be in the shadow of a barrel profile. This is with a very heavy gauge metal also to give a lifetime warrantee. Their screws are even larger, and the heads are capped with a vinyle hex head about a 7/16" size but it disappears nicely in the shadow. That vinyl cap is nice because a lot of screws get the paint damaged in the installation process and rust happens.
Hope this explains why the pans are the prefered position for placement points. I'll be glad to let anyone else make points why they prefer to puncture the ribs instead..
Excellence is its own reward!
I've been putting the 2.5's in the large ribs for fifteen years and have been told a few times that thermal expansion can cause the screws to tear through the roofing. I've never had a problem though (no call backs) and I don't like the way screwing on the flat spot causes the overlapping rib where the sheets join to pull slightly off center. I always thought it was better to screw through both sheets at that point. For what it's worth.
I'm putting this kind of roof on a detached garage I'm building here in Florida. Down here, this style is called a "5V crimp" roof because, naturally, the panels have 5 v-shaped crimps in them.
The current documentation I have only calls for putting screws in the field, or, as an alternate fastening method, nails on the peaks. Why anyone would use nails over screws is beyond me. Other manufacturers in my area recommend putting the screws in the peaks.
The recommended screws are 1 1/2 inch #10 with the spacing dependent on the wind load and zone, though some manufacturers say a #9 is ok.
"Putting them in the ribs ... there are a half dozen reasons not to do it with this ribbed panel type of roofing - but that's mostly another subject."
I've never heard a compelling reason to either put them in the ribs in the flat area.
Besides - Putting them in the ribs MUST be right, 'cause that's the way I've always done it.(-:
"Mine that were pulling out were 1" put into 1" lumber. "
Not sure why you would have been putting them into 1" lumber. Every post frame I've built had 2X purlins.She got her good looks from her father. He's a plastic surgeon.
Boss, this is my house, not a post shed. I framed with 2x8 @16"oc and then 1x6 purlins/strapping @24"oc for fastening. Actually, I think that I used the 1x6 @ 12" oc but only needed to screw down every other one.
On you sheds, I'll wager that the roof rafter framing or trussing was greater than 16"oc so the 2x would be needed to span that gap.
Excellence is its own reward!
Do I understand correctly that you installed the metal directly over the skip sheathing - no felt?Any jackass can kick down a barn, but it takes a carpenter to build one.
That's right, I'm feltless.
But if I had it to do over again, I would sheath with plywood, dry in with tarpaper, strap (furr out) over that with the purlins, and then screw the metal with 5/16 fasteners..
Excellence is its own reward!
I'm guessing: Are you thinking that you wouldn't screw metal directly to the tarpaper because the tarpaper gives a little? Or because the screws might bite better in 1x than plywood? Or what other reason for not putting metal directly on felt?Any jackass can kick down a barn, but it takes a carpenter to build one.
There is a potential (however, probably pretty small) for a reaction between the asphalt in the felt and the metal. The idea situation is to isolate them as piffin describes or with rosin paper. I like the new roof membranes (rooftopguard II, titanium, etc.) for this type application in lieu of felt.
Just went out and looked over my garage. Roofed it with "Pro Panel" 6 years ago. Thicker 5/16 head screws. Short runs: Each side is about 8 feet. Windy/hot/cold location. None pulling up as far as I can see (I got up on a ladder). They are driven into 1x4s. Brown color.
Haven't gone to look, but I repaired a similar roof in '95 here. Only the leading (wind) edge was loosened. I replaced the loose screws with the larger diameter and added a number of much longer screws that went down into framing members where I could hit them. That roof is also a gable with about 20 feet on each side and also brown. Owners are friends and they've never mentioned any continued problem.
I've put similar metal over plywood and felt and also over a 1x grid that lifted the metal 1 1/2 inches off the felt. I never heard of any problem with it, but moved away only four years after I built it.
I've installed similar material lots of times but often never got feedback. Maybe all those roofs have blown away by now. : )
Somehow I got the idea that darker colors are worse for stated problem (and for color fading). Whatcha think?
I'm planning on putting same on new place. Plan is to put galv-alum type directly onto a double layer of 30# felt over 3/4 plywood sheathing. I'll use the larger screws.
Question: Local lumberman glazes over when I ask for matching metal ridge vent to go with the Pro Panel. Any suggestions or thoughts?
Any jackass can kick down a barn, but it takes a carpenter to build one.
As to Ridge vent. Our local roofer buys flat stock from the same supplier as his metal roofing and then shears and bends his own ridge vent, drip edge, and end caps depending upon his needs.
Our red roof has been on three years and so far is doing OK. Screws are into 1 x 4 yellow pine on 24 inch centers. 1 x 4 set on 30# felt on OSB -- SIP panels. Screws are 1 1/2 to go through 1 x 4 and OSB both.
deblacksmith
I'm betting that with longer screws through a dual material you would have some extra tewnsion built in to resist pullout..
Excellence is its own reward!
Get a woven stuff - I thoink it's called coravent or something like that - dark and cold here now so I am not running out to the shop to look at it.
Anyway, you can use the regular ProPanel ridge and this suff will compress under it. It keeps the bugs out and slows wind driven snow or rain. There are more complicated was to go but this seems to work for me..
Excellence is its own reward!
Cobravent....its like furnace filter material, comes in 20 foot long rolls.
Cobra ridge vent, maybe? That's what I was thinking of doing. Glad to hear it's already been tried!Any jackass can kick down a barn, but it takes a carpenter to build one.
Check this site out: http://www.profilevent.com/index2.html
Edited 10/12/2003 5:10:19 AM ET by greencu
Thanks for the lead!Any jackass can kick down a barn, but it takes a carpenter to build one.
Rib Steel Vent-
Matching J-channel on the top edge of the steel, Cobra Vent or Cora Vent, Ridge cap with long screws.
Garett
Just 'cause you explain every six or seven months why to screw into the flats, doesn't mean it works, and it still hasn't convinced me<G>
I'm not a roofer by any stretch of the imagination, but, I have put on around 20 metal roofs (or is that rooves?). 2 were a galvalume type with flat-topped ribs, the rest were the 5 vee farm style, and two of those were my own houses. Every one of those were fastened through the ribs (okay, and in in the flats at the gables).
I started, back before screws were invented, using lead-heads. A pretty sketchy sealing dealie, but nailed through the top of the 5 vee ribs, I never had a leak. I lived in a house for 6 years that had the roof fastened like this, no leaks. Used rough pine 1x4 purlins (cured for 3 months of Virginia summer weather).
New house has 5 vee screwed down. 1/4" x 1 1/4" screws into pine 1x4. We'd measure on the roof, punch with an awl, then screw. I posted this before and you suggested that I learn more about screwing (dang if Mrs 'Snort doesn't agree), but these free screws I got from a contractor buddy would get some of the washers bunched up, we'd replace them and move on. On a later job, I used Sun or Sun-Tuff brand and didn't have nearly the bunching. Anyway, we went through the ribs and were very careful about getting the washers to seat right. I did get a leak where the awl slipped off the rib top and went into the flat, guess I should have screwed it there!
I've used ring shanked nails with the rubber washer through the ribs on our shop thru the vees. I've fixed old (not done by me or anyone near my old age)barns and sheds, and none appeared to be leaking from the tops of the vees.
I've been in buildings that had recycled "tin" on them. You could see daylight through the old nail holes in the vees and it could be raining like all get out and no leaks.
Anyway, my theory, and danged if that Aussie's screws didn't reinforce it, is this:
Sometimes, just 'cause they always did it like that, the old timers are right. You've got drilled holes in your panels that are bigger than your screw threads. The screw isn't attached to the roofing. The much thinner roofing is moving a whole bunch more than the screw, and the roofing is moving up and down cause the screw threads are only gripping the wooden purlins. You roofing could be floating, maybe it's rattling your screws (we get some pretty heavy winds, and I've never seen anything close to your description of wind under tin w/ rib thru srews). Maybe daily thermal cycling is pulling your screws loose? I've never seen any one put a metal roof down here with a Tech? screwdriver, whassat?
EliphIno!
Well, you are sure right that most of the holes placed in high ribs are far less likely to leak unless a raindrop happens to hit dead splatter right on center of the hole, but you are sure describing a slow way to install them. ;)
A tecdriver is a - well mine is the same motor and body and trigger as the Milwuakee 3/8"VSR but the nose has a friction clutch. I looks and works really similar to a sheetrock screwgun, except the nose cone is heavier and is removeable so I can put different tips in it. I've got four different tip housings to fit it. The bit is a magnetic socket set that snaps into it on the 1/4" hex drive.
I think you were the one who expounded the thermal expansion theory but I still don't think you have explained how a longitudinal movement in the steel will translate to a rotational movement in the screw. maybe it's like sex, where a good longitudinal action will make your head spin.
;)
I'd be glad to hear something more technical
.
Excellence is its own reward!
I'm not quite sure what you mean by j channel on top edge of steel. Thanks for your response!Any jackass can kick down a barn, but it takes a carpenter to build one.
Use the J-channel to cap the peak end of the steel (where the ridge cap will cover it) then lay cobravent over the j-channel and attach ridge cap with screws thru the cobra, thru the J, thru the steel pannel and into a purlin or the roof deck. I wish I could post a drawing.
Hi Piffin
We do a lot of Metal Roofs here down under. In the past we have had problems as you describe but this has been alleviated by 1. Using metal top hat roof battens and 2. using this type of roof screw http://www.buildex.com.au/corrosion/shankguard.asp
regards
mark
quittintime
Mark, That is an interesting screw. I see that it self drills and that it opens a slightly larger hole in the metal than the shank size, though for a different reason than I plan. They make a good point. A lot of the screws I removed had the galv coating stripped off and rust starting where they shank had rubbed on the steel going in.
your use of top hat steel for attachemnt probaly allows the top hat to move/flex with thermal expansion?.
Excellence is its own reward!
I haven't seen much literature or science on loosening screws - but there's a lot out there for loosening bolts. I ran across this which might be of interest to you. Most of the document doesn't apply, but check out pages 5, 6, and 32. I'm not sure how accurate all of it is, but perhaps it may give you some insights:
http://www.atlascopco.com/tools/products/website.nsf/0/55743a831415c87fc1256cc90045a2ff/$FILE/Pocket%20guide%20screwdrivers.pdf
Andy
It seems like all the ones that I have had problems with were a combination of 1/4" machine thread screws into OSB.
I now order the more aggresive 5/16" screws on every roof whether its OSB, CDX or 1x4 skip sheeeting.
Dave
Thankls,
That took a while for the pc to process with all the graphics it contains but I saved it for deeper study later.
Thjose pages suggested that it doesn't take much between optimum torque and over-torque to ruin a screw joint, only around 10% and that can vary according to size of fastener and materials being joined.
That leads me in a new direction of thought. I had reasoned previously that the green lumber had only played a small part in this scenario. But if that lumber was green enough to be soft and squirrely (note my use of highly technical terms here) then it is conceiveable that just as the screw was coming to the torque point where the clutch was kicking out and the gasket deating, the threads of the screw were just starting to strip out the wood fibre in the hole. This would be consistent with the fact that I found the loose screws scattered across the roof randonmly.
It also gives me comfort that by replacing them with larger diameter screws having more surface area (friction) in the thread that is now penetrating dry wood, I may have overcome the problem.
This whole thread so far with all the various reponses also confirms my initial instincts of over 25 years ago, that the larger diameeeter screws should always be used and that the dinky little ones are only for cost cutters. It all makes me wonder why any manufacturers recommend them.
.
Excellence is its own reward!
Another question: other than for looks, why drill? All the screws I've used we just screwed right through the metal - no drilling.
Given what I"m reading here regarding the screws biting, does it make any sense to you to think that even the smaller screws would work better if screwed into 2x skip sheathing that is bone dry? (assuming a screw long enough to bite all or most of the thinckness of the 2x)Any jackass can kick down a barn, but it takes a carpenter to build one.
There are different kinds of drilling tips. Every one i have seen though requires that you put some weight behind the screwgun to get it started into the steel. Pushing down on the gun pushes you away from the roof.
That is not an ideal situation except on a lowslope roof.
If the guns you are using are battery operated, the screwing time is about a third as long so the battery will run longer up on the roof. I use a corded drill to make the holes in the stack on the ground. Anyoine who haas ever done it Bucksnorts way, with a tape and a punch, and then sees me in action, says, "Hey cool man. How come everybody doesn't do it that way?"
Must like purple thumbs.
Excellence is its own reward!