Corrugated metal screwed high and dry, but AG metal down low and wet..

[rerod]

Hi folks.

I know AG metal manufactures say to screw through the low flat section, and they say it's because screwing through the high rib, with much less chance of a LEAK, will deform the rib since its hollow.. But Ive also read old timers swear they will always screw through the rib, because they were taught this way 50 years ago installing corrugated with nails..

I see pictures of new corrugated metal roofs screwed through the high part of the rib/wave.. Is this because the rounded shape of corrugated metal has more compressive strength?

Because of this high dry screw, low wet screw issue, corrugated roofing (if screwing through the high rib is correct) has the advantage IMO. I'm not sure me using the word issue is in correct context here, because leaks can be devastating and here we go drilling a bunch of holes through a perfectly water tight roof panel.

Or is it the fact the old timers had good luck up high because a 10' panel will expand/contract 1/4" in most climates, elongating screw holes and unscrewing screws when screwed down in the low's? Because placing a screw on the high rib would place the screw sticking out of the wood 1" and might allow the screw to flex enough to not egg the metal out?

Anyway, I like snaplocks hidden fasteners, but don't like how the manufacture double the price pound per pound going from AG metal to snaplock. I'm trying to figure a way to reduce my chances of a exposed fastener leak if I choose to go that cheaper route.

I noticed the nail holes in my old corrugated barn roof don't leak long after the washer dried up and fell off. Even with a nail missing.. Why? I'm guessing because the nail hole is on top of a rib drastically reducing the amount of water introduced to it since the water wants to flow down hill..

Thanks

 

[PugetDude]

If you want it to leak nail it through the ribs, where the 1-1/4" screw that is sticking out of the sheathing can act like a lever during expansion and contraction, deforming the ribs, elongating the hole and imparting reverse bending stresses on the root of the thread.

Or you could secure it down tight, compress the sealng washer properly without deforming the panel, and eliminate the issues caused by having the screw waving in the weather by screwing through the flats.

What other application do you leave a fastener standing proud of the surface you're trying to secure? Screws rely on clamping forces to perform to spec. You can't clamp a panel that is standing an inch above the substrate you're screwing into. It may feel snug initially, but it won't stay that way.

Your great-grandpa used to get down off a homemade wooden ladder to adjust points and condenser on his truck after nailing down the barn roof through the ribs with a sack of ring-shank nails and rubber washers and slathering the leakers with tar.

Technology has changed. The price difference you're bemoaning reflects the difference in manufacturing costs, the value-added characteristics of the panel and the difference in material costs.

 

[rerod]

Securing the metal in the flats and tight doesn't prevent the panel from changing length and egging out all the holes, unscrewing screws, ruining washers. Prove to me fastening through the ribs leak more.

Placing the holes low and wet also places all those holes right where the most water collects/stands. That's why standing seam is, standing..

My old barn roof from inside at dusk looked like a star filled sky all those unfilled holes that didn't leak because they were on top on the rib.

 

[850xpeps]

Screwing on the rib is pour installation technique and ugly. Screw on the flats. It’s a slipped roof so water doesn’t sit. Get your laps nice and tight. It’s referred to as stitching up here, when you screw on the rib. And imo should only be a last resort to keep that joint tight. The screws will move there more because of the 2 layers of tin. But screwing on the flats doesn’t stop the rib from moving and popping screws out.

 

[Mattlt]

Note how Metal Sales (one of, if not the largest supplier of steel) recommends a shorter fastener on the joints where the two sheets overlap. This screw would only be holding the two sheets together, never touches the wood.

https://www.metalsales.us.com/wp-content/uploads/2020/03/Post_Frame-Installation_Guide.pdf

Is it just my memory, or were there different rules years ago for sidewall vs roof steel? I thought roof was on the flat and sidewall was on the rib? Maybe I'm remembering that wrong.

For what it's worth, the building I had built in 1995 is nailed on the rib, both roof and sidewalls, except on the ends of the panels so the ribs don't crush. Hasn't leaked yet. Not saying that's the way it should be done now but this one has worked out.

I think the color of the steel has a lot to do with it too. Darker colors expand and contract more causing more problems with the fasteners.

 

[rerod]

For what it's worth, the building I had built in 1995 is nailed on the rib, both roof and sidewalls, except on the ends of the panels so the ribs don't crush. Hasn't leaked yet. Not saying that's the way it should be done now but this one has worked out.

Yup. I bet the guy who ran that crew was older, because that's how metal used to be installed back then. Nails on top of the rib where only a direct hit from a rain drop could make it in.

I bet the industry changed their tune when they started offering lighter gauges of metal where the rib couldn't withstand the pressure of a fastener.

Or you could use stealthbond metal roof adhesive.. lol. Hey why not. They glue airplanes and cars together lately..

 

[PugetDude]

Securing the metal in the flats and tight doesn't prevent the panel from changing length and egging out all the holes, unscrewing screws, ruining washers. Prove to me fastening through the ribs leak more.

Placing the holes low and wet also places all those holes right where the most water collects/stands. That's why standing seam is, standing..

My old barn roof from inside at dusk looked like a star filled sky all those unfilled holes that didn't leak because they were on top on the rib.

Were you posting for professional advice or just blogging?

Every panel and screw manufacturer recommends fastening through the flats for a reason, but feel free to install yours anyway you want.

BTW, several manufacturers offer oversized “rescue screws” to fix panels that were screwed through the ribs.

Paging Readhead...

 

[rerod]

Were you posting for professional advice or just blogging?

Every panel and screw manufacturer recommends fastening through the flats for a reason, but feel free to install yours anyway you want.

BTW, several manufacturers offer oversized “rescue screws” to fix panels that were screwed through the ribs.

Paging Readhead...

I appreciate advice, but Id like to know why the industry shifted from nailing the ribs, to nailing the valley's. And I don't buy your reason why or agree when you say "thermal expansion and contraction will work them loose if the sealing surface is 1-1/4"-1-1/2" above the substrate."

That 1-1/4"-1-1/2" above in the rib has nothing to do with the screws loosening, and they will loosen just as fast screwed low in the valleys.

And rescue screws have nothing to do with repairing a rib. Rescue screws are simply oversized to fit stripped out holes in the wood or cover elongated panel holes which in my opinion, where egged out even bigger than if the installer had screwed through the ribs. And obviously has 100% more chance of leaking located low in the valley.

 

[readhead]

PD has already said all the right things. Screw in the flats and stitch the ribs if necessary. You already know everything about this so I'm not sure what we can help with.

 

[Hot Rod Grampa]

I installed a metal roof from Ideal metal. According to their installation manual, they tell you to use 2" screws through the rib. That is how I did mine. It forces you to screw with caution and use a clutch type drill. Bought a corded drill with a clutch just for that job. 7 years later still no leaks and no loose screws.

 

[readhead]

Those damn manufacturers just don't know anything about their own product. Someone needs to set them straight.

 

[850xpeps]

I installed a metal roof from Ideal metal. According to their installation manual, they tell you to use 2" screws through the rib. That is how I did mine. It forces you to screw with caution and use a clutch type drill. Bought a corded drill with a clutch just for that job. 7 years later still no leaks and no loose screws.

You climb in your attic and check when raining?

Those damn manufacturers just don't know anything about their own product. Someone needs to set them straight.

Bang on. I had to tell the mfg what flashings and sizes to supply with the snap lok tin I was buying from them. Lol they quoted me regular screws with washers. I said if I wanted holes all over my roof I’d buy regular tin at 1/2 the price.

 

[Hot Rod Grampa]

Yes I have nothing better to do than climb into my attic with a bright spotlight and search for leaks during every rain. Seriously. Do you think before you type? Everything isn't always about you. I answered the op. Gave him facts. You? Never mind. Don't bother.

 

[850xpeps]

Yes I have nothing better to do than climb into my attic with a bright spotlight and search for leaks during every rain. Seriously. Do you think before you type? Everything isn't always about you. I answered the op. Gave him facts. You? Never mind. Don't bother.

Because everyone and their dogs say they don’t leak but has never looked. They just assume it isn’t leaking because their ceiling isn’t dripping.

No reason to be an as*hole about it. I’ve climbed and peaked on occasion into my attic and sometimes when it rains. But I take pride in what I do and also want the experience to back up my suggestions. And I want to make sure my house isn’t leaking.


What fact did you give him? You just said it’s fine. What kind of fact is that. If you don’t check it to see if it leaks how can you call that a fact?

I gave the op my opinion on years in the trade of building houses and commercial buildings.

 

[58Yeoman]

I didn't build my steel building, but bought it in 2008, and I think it was built around 2000. All the screws/washers are on the ribs, top and sides, and It doesn't leak. That's all I'm saying.

 

[Dustball]

Taken from another board-

This argument is primarily due to the use of lead headed nails used back in the old days. Because they did not completely seal the hole in the panels, you had to put them up out of the water flow. These days, with fasteners with neoprene washers, you can fasten the panel in the flat where they are slightly less obtrusive. You don't say what type of panel you are using. If you are using a panel with a tall rib, you run the risk of overtightening the fastener and colapsing the rib. Also, when the fastener is in a rib, it can experience more prying action as there in not much to keep it straight. Engineers do not like to see fasteners installed in this manner. Now if you are looking at a 5V Crimp panel as is often used in Florida, many people put the fasteners in the top of the V instead of in the flat. While it is common, it makes no sense to me. While the prying action is not as bad as in a tall rib panel, you have a much harder time getting a fastener started in the top of the V (some folks turn the stack upside down and predrill them, others hit the top of the V with a hammer at the fastener location to flatten it out a little). In this instance, imagine what you are doing to the neoprene washer as the fastener tightens and rubs and catches on the V. In the commercial industry, we use the same type of screws (the heads and washers are the same) on roofs that are up to 800' from eave to ridge at a 1/4:12 roof slope. That means the fastener heads are submerged in even a light rain. We do not have a problem with fasteners leaking (as long as they are properly installed. The bottom line: people successfully do it both ways but you have a lot less chance of a problem and better uplift resistance if you put them in the flat.

 

[PugetDude]

I appreciate advice, but Id like to know why the industry shifted from nailing the ribs, to nailing the valley's. And I don't buy your reason why or agree when you say "thermal expansion and contraction will work them loose if the sealing surface is 1-1/4"-1-1/2" above the substrate."

That 1-1/4"-1-1/2" above in the rib has nothing to do with the screws loosening, and they will loosen just as fast screwed low in the valleys.

And rescue screws have nothing to do with repairing a rib. Rescue screws are simply oversized to fit stripped out holes in the wood or cover elongated panel holes which in my opinion, where egged out even bigger than if the installer had screwed through the ribs. And obviously has 100% more chance of leaking located low in the valley.

The industry shifted from nailing in the ribs to screwing in the valleys. Technology changed.

A screw protruding 1.25" to 1.5" above constraint in a solid substrate sees much greater side-to side movement when a lateral load (expansion/contraction/snow) is applied than one seated .025" above the same solid substrate. Your opinion isn't supported by the laws of physics.

Rescue screws are larger than regular washer-head screws and designed to bite and seal where a smaller screw has failed. Failure is usually from a screw loosening and allowing water intrusion that degrades the structural member it's screwed into. Read the previous paragraph for the primary cause of screws loosening

Clearly you believe you know more about screwing down metal roofing than anyone, and started this thread only to argue your industry-contrary vainglorious opinion. I'm surprised I never ran into you as a subject matter expert in my 35+ years in the Metal Building Industry. Maybe Readhead has met you, he's been at this longer than me.

What would you recommend for removing stumps?

 

[matt_i]

The industry shifted from nailing in the ribs to screwing in the valleys. Technology changed.

A screw protruding 1.25" to 1.5" above constraint in a solid substrate sees much greater side-to side movement when a lateral load (expansion/contraction/snow) is applied than one seated .025" above the same solid substrate. Your opinion isn't supported by the laws of physics.

I'd say a long nail has a much greater chance of springy elastic compliance in cantilevered bending as the metal moves thru thermal cycles. Nail close/tight to the wood support and its either going to egg the hole by tearing the sheetmetal or pull the nail out by loosening its friction grip over time.

Screws are much more resistant to staying where one put them in either case.

 

[rerod]

Those damn manufacturers just don't know anything about their own product. Someone needs to set them straight.

Yes, those manufacturers are the problem when they changed their recommendation from nailing the rib to the flat. Or maybe they never recommended either way. The industry cant make up it's mind and decided to go with the better looking option imo, or the fact 26g AG metal will deform when its rib is screwed.

No ones answered my original question about "why do corrugated roof manufacturer's continue to specify screwing the ridge", among at least one AG metal manufacturer reported by Hot Rod Grampa?

It doesn't take a professional roofer or engineer to figure out water flows down hill, and that screws will loosen fastening a 10' sheet of metal in most climate's.

I'll take my chances on the loose screw up on the rib.

Wouldn't we have better luck with AG metal's fastener issues if the manufacturer rolled the ribs the short way? Meaning that all the expansion and contraction forces would be put on the 4' side of the sheet instead of the 10' resulting in less than half of the movement or egging. Just another one of my opinions..

 

[850xpeps]

I’m the end, they both have the same likelihood of leaking. Done properly with no screw on the ridge(stitch), or with screwed on flats and the stitch. The bigger influence will be the installer. For the first reason being no real difference, it comes down to appearance and in my opinion a stitched seams don’t look as mice and clean as the other option. Some tin is sh!ttier than. Others and requires the stitch to keep the lap nice. On top of garbage tin these days, short screws on the stitch might not be a good idea because the tin doesn’t have much holding power on a course thread screw.

 

[PugetDude]

I’m going to leave this thread to the “experts”, and get back to installing my wallpaper with carpet tacks.

 

[Dustball]

No ones answered my original question about "why do corrugated roof manufacturer's continue to specify screwing the ridge", among at least one AG metal manufacturer reported by Hot Rod Grampa?

Because a washer doesn't seal against a concave surface.

 

[readhead]

Clearly some people don’t recognize sarcasm when they see it. If you are not sure about proper install details consult the manufacturers instructions. I have been installing sheet metal for over forty years and have never come across a supplier that recommend fasteners in the highs except stitch screws. To be fair I have not installed metal from every supplier but there is a trend.

I’m pretty sure this argument has been around since metal roofing came on the scene. The product and fasteners have evolved over the years to what we have now. We install screws in the lows on corrugated all the time with no leaks. Washers on screws are far better than in the past. Fastening screw failures in high ribs are due to simple physics. As the panel expands and contracts the lever action on the screw will cause it to fail. This is a bigger problem in wood than metal framing.

In this particular case there is a pretty clear consensus according to manufacturers on the correct way to install metal roofing. But there will always be the people who know better. That is good because it brings me business when the next owner of that building calls and wants me to come out and figure out why the roof leaks or is pealing off because the screws have gone missing.

Now I have to go buy some more tacks for PD because he can’t leave the house.

 

[850xpeps]

Clearly some people don’t recognize sarcasm when they see it. If you are not sure about proper install details consult the manufacturers instructions. I have been installing sheet metal for over forty years and have never come across a supplier that recommend fasteners in the highs except stitch screws. To be fair I have not installed metal from every supplier but there is a trend.

I’m pretty sure this argument has been around since metal roofing came on the scene. The product and fasteners have evolved over the years to what we have now. We install screws in the lows on corrugated all the time with no leaks. Washers on screws are far better than in the past. Fastening screw failures in high ribs are due to simple physics. As the panel expands and contracts the lever action on the screw will cause it to fail. This is a bigger problem in wood than metal framing.

In this particular case there is a pretty clear consensus according to manufacturers on the correct way to install metal roofing. But there will always be the people who know better. That is good because it brings me business when the next owner of that building calls and wants me to come out and figure out why the roof leaks or is pealing off because the screws have gone missing.

Now I have to go buy some more tacks for PD because he can’t leave the house.

I misunderstood then. I assumed we were only talking about adding the stitch. In my short time I’ve never seen anyone screw entire sheets on the rib.

 

[Kevin54]

Does anyone use the supports anymore to keep from pulling down the ribs too far and deforming it?

 

[readhead]

Kevin, that material was designed, from what I can tell, back in the fifty's to support fiberglass panels when patio's were becoming all the rage. I think that profile still works with the light gage corrugated panels usually sold at big box stores.

 

[rerod]

In this particular case there is a pretty clear consensus according to manufacturers on the correct way to install metal roofing. But there will always be the people who know better. That is good because it brings me business when the next owner of that building calls and wants me to come out and figure out why the roof leaks or is pealing off because the screws have gone missing.

Now I have to go buy some more tacks for PD because he can’t leave the house.

There is no consensus at all when manufactures disagree. Other countries exclusively screw through the rib. Australia and New-Zealand to name a few, exclusively fasten through the high rib.

Which makes sense because why would you want to penetrate where the most water is? They must not know anything..

In my 40 days in the roofing industry, this cut and dry about screwing the lows being "best practice" isn't cut and dry at all. When there are two clear camps swearing their method is the best.

Does anyone use the supports anymore to keep from pulling down the ribs too far and deforming it?

Are those available Kevin? What are they called?

 

[readhead]

Now you are throwing other countries into the equation. They are south of the equator and everyone knows that everything there is backwards.
You have absolutely proven your point. Most of the manufacturers are doing it wrong. You should give them a call.

 

[Kevin54]

There is no consensus at all when manufactures disagree. Other countries exclusively screw through the rib. Australia and New-Zealand to name a few, exclusively fasten through the high rib.

Which makes sense because why would you want to penetrate where the most water is? They must not know anything..

In my 40 days in the roofing industry, this cut and dry about screwing the lows being "best practice" isn't cut and dry at all. When there are two clear camps swearing their method is the best.


Are those available Kevin? What are they called?

They are either called closure strips or corrugated panel supports. They still sell them.

 

[rerod]

They are either called closure strips or corrugated panel supports. They still sell them.

Thanks

As the panel expands and contracts the lever action on the screw will cause it to fail. This is a bigger problem in wood than metal framing.

I imagine expansion contraction rates of the roof compared to the structure would be the same, when the structure is the same material..

 

[PugetDude]

I imagine expansion contraction rates of the roof compared to the structure would be the same, when the structure is the same material..

Yep, the air between the purlins is going to expand the frame at the same rate as the roof.

Keep digging, you're making good progress.

 

[kaymccampbell]

If you want to avoid the conundrum of valley or rib, and the joy of watching your expensive snap locks peel back, go with standing seam. Done right it'll never leak. Mine don't. And there are no exposed screws or nails, and lock strip to pop. And you get a fantastic upper body workout squishing the crimper tool.

 

[metlmunchr]

I’m going to leave this thread to the “experts”, and get back to installing my wallpaper with carpet tacks.

Now that's a great idea. Just think how easy it'll be to strip it when the dear wife gets tired of the current pattern, but for some unknown reason, the R & R becomes your job even though you don't see a damn thing wrong with the stuff that's up there now.

 

[Bert_]

They are either called closure strips or corrugated panel supports. They still sell them.

Any closure strip I have seen was foam.

I haven't seen anyone fasten through the rib since nails were being used.

Ever since screws became common it was recommended to go in the flat. It only makes sense. There might be less water flowing on the rib but that doesn't matter if you can't keep the washer compressed since there is nothing underneath to support it.

 

[rerod]

Yep, the air between the purlins is going to expand the frame at the same rate as the roof.

Keep digging, you're making good progress.

The purlins don't need to expand because the ribs absorb horizontal expansion.

It's the trusses that will expand at the same rate when your talking about a roof only ,or open air car port structure like I'm considering.

But since you realized you were wrong, I understand where this is going with you PugetDude. take care

If you want to avoid the conundrum of watching your expensive snap locks peel back, go with standing seam.

I might just go standing seam in the end kaymccampbell.. But Ive also considered pro-snap or snap-lock but never heard of it "peeling back".. You mean you witnessed the lock release and the panels separate?

Thanks

 

[PugetDude]

The majority of Ag panel is installed on post-frame or wood-framed buildings. With wooden trusses.... with a much different coefficient of expansion than a steel beam.
Try again.