Thread: Corrugated Metal Roofing

Screws on the ribs or in the flats?

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Ribs, not that you won't have leaks anyway.
Use the screws with neoprene washers or lead head nails. The washers will crack long before the sheet metals life is over but at least it is a start and the screws should have better pull out resistance than the nails, maybe lead head ring shank nails would be close to the pull out resistance.

I've seen arguments for both ways. What does the manufacturer say?

Originally Posted by Michael Schirmer

Screws on the ribs or in the flats?

On the ribs. (In spite of the fact that my HI training says; in the flats.)

Originally Posted by Michael Schirmer

Screws on the ribs or in the flats?

The instructions for the ribbed metal roofs that I have seen require attachment in the flat sections using screws with attached neoprene washers. If the screws go into the raised ribs, they will flatten-out the ribs and create layout problems (probably others as well). Standing seam roofs and batten seam roofs, on the other hand, are attached alongside the channels and covered by the next channel or batten.

Look here for basic information:
Installation information for metal roofing and siding - Metal Roofing Wholesalers.com
Tuff-Rib | Classic Rib | Metal Roofing Panel | Best Buy Metals

Or use the installation instructions from this company.

Maybe we are talking about different items. When I envision corrugated metal roofs, I see barn roofs with a continuous curve like a sine wave, so there are no real "flats" only valleys. If your talking another style of metal, then follow the manufacturers instructions. (you will still get leaks in the valleys using washers to seal though)

FLEXOSPAN - Roofing & Siding Panel - Corrugated CAD Drawings

Go by whatever the manufacturer says.

I've seen different manufacturers state in the rib and the other state in the valley.

The one stating in the rib says that in the valley will leak because it blocks the drainage path.

The one stating in the valley says that in the rib will leak as it flattens the rib out and comes loose because there is nothing to tighten down to.

Originally Posted by Jim Luttrall

Maybe we are talking about different items. When I envision corrugated metal roofs, I see barn roofs with a continuous curve like a sine wave, so there are no real "flats" only valleys. If your talking another style of metal, then follow the manufacturers instructions. (you will still get leaks in the valleys using washers to seal though)

FLEXOSPAN - Roofing & Siding Panel - Corrugated CAD Drawings

Jim,

Yes, the diagram in your post is different from the one in mine. As far as I know, the corrugated (your post) panels do require the attachment at the peak of the corrugation rather than the valley. However, a "wiggle mold" is typically available to support the corrugations and prevent crushing. Not sure if it is approved, though.

I meant the ribs and flats type, not the wiggle type seen on barns and sheds.

The answer is political.

This was bothering me because I knew what most all manufacturer's installation instructions say and needed to remember where I previously got my information. Can anyone confirm or deny this story?

"It was from a member of the National Roofing Contractors Association. With the invent of self-tapping neoprene gasketed screws (fairly recently), metal roofing manufacturers felt they could increase their market share by making the roofing easier to install for a DIY'er and roofers alike by eliminate pre-drilling the metal on the ribs for the old lead washer nails or lead headed nails. The instructions for nails still say on the ribs and not in the flats on most mfg. instr. I've seen.

Old time roofers still continued to pre-drill on the ribs while the sheets were stacked flat on the ground, but then used the new gasketed screws anyway. If screw pops developed or the gaskets rotted, it was still less of a problem because the water runs in the flat areas.

Inexperienced roofers followed the new manufacturers instructions and complained about call-backs from screw pop leaks or warranty claims as the neoprene gaskets deteriorated or cracked causing leaks long before the end of the metal roof warranty. The NRCA members have been petitioning metal roofing manufacturers to change their installation instructions as now the gasketed screws have had enough time to be field tested. You should never use fasteners or materials incorporated into the fasteners that have a lesser life expectancy of what's being fastened.

I will change my comments to remove the 'not properly installed' wording and just say 'not ideal per some roofers and monitor for screw pops, which can cause leaks when located in the flats'.

I believe we still have to say something because you and I both know that a homeowner will be chasing us if the roof leaks, not the manufacturer of the roofing who is saying to install screws in the path of the water with gaskets that will not outlast the roof..."

Forgot the picture:

You're right to call it out as a heads-up to a new owner, even if it's not leaking yet.
The pic shows one screw popped out and there are icicles below the other two fasteners. Runoff heads straight to the lowest point, right where the screws are. Screws come loose. It will leak.

I thought we were talking about a roof for something like a pole barn.

That type of roof for a house-- huh uh. I very rarely see them used on a house in this area, and when I do, I tell my client that these roofs are not intended for a residential structure. I tell them that these roofs will leak sooner or later, and recommend replacement.

Originally Posted by Michael Schirmer

I meant the ribs and flats type

Most of those manufacturers state in the flats and specifically state NOT in the ribs, for the reasons stated above - fasteners in the ribs have nothing to tighten down to and are prone to leaking.

Nothing political about that, simple empirical data showing what works and what does not, and why it does not.

Looks like that roof is getting into some pretty rough shape.

From the dip (Bow) we see in the picture we can see that the roof has suffered some distortion propably due to snow loads.

THe popping of the screws denotes that there may have been excessive loads on the roof as well as some movement of the metal sheathing.

If the underlying structure is sound and has not suffered any damage. This roof can be easily repaired to prevent further damage and eliminate the possibility of leakage.

Given the life span of these type of materials they usually can last 1000 yrs.

Also from a cosmetic point of view they can be repainted,. Many good paint products specifically for metal roofs exist - since they need to be more flexible and more resistant to the elements.

If no snow breaks are present it would be a good time to install some.

Cheers from the great white north - EH!!!!!! lol

Originally Posted by Jerry Peck

Most of those manufacturers state in the flats and specifically state NOT in the ribs, for the reasons stated above - fasteners in the ribs have nothing to tighten down to and are prone to leaking.

Nothing political about that, simple empirical data showing what works and what does not, and why it does not.

We have a ton of roofs like this up here in the north. The ribs are the rigidity of corrugated metal. 90% of the roofs like this do have the screws on the ridges in spite of what mfgs. say just because of the leaking and roofer experience (the water runs in the flats). The roofers set their screw clutches to avoid over-driving and denting.

Originally Posted by Michael Schirmer

We have a ton of roofs like this up here in the north. The ribs are the rigidity of corrugated metal. 90% of the roofs like this do have the screws on the ridges in spite of what mfgs. say just because of the leaking and roofer experience (the water runs in the flats). The roofers set their screw clutches to avoid over-driving and denting.

There are a lot of potential problems from doing it as you say they are doing it in your area, not the least of which would be trying to get anything from the manufacturer regarding any warranty issues as the roofer voided the warranty at the time of installation.

Just because "that is the way it has always been done here" or "that's the way we do it here" does not make it right, in fact, it makes it mean nothing at all - THE ONLY ACCEPTABLE method of installation is as stated in the manufacturer's installation instructions ... THAT is the only way it was test, approved, and received its product approval ... any other installation is on the roofers back and money, not that of the manufacturer.

And you know how far you can take most roofers work ...not far, and knowing it is "wrong" to start with just adds your name to the list of defendants when the time ever comes.

Just got my first call ever to inspect a property with a corrugated metal roof - you just never see them here.

Can anyone point me to a guide for inspecting these roofs?

Oh, and the buy says it's a FHA loan - and a on-line search turns up the following:

"... acceptable w/certification that roof was installed per manufacturer's specifications."

Who certifies this?

And since (it seems to me) it's probably often difficult or impossible to identify the manufacture, is there some sort of industry trade association installation guide that you can fall back on for "industry best practices"?