Metal roof installation advice

[meball]

Hi, I am finally putting the roof on my pole barn. I used 16foot 2x6's placed every 2ft with 1x4 strapping every 12". I am installing 36" sheets of Duraclad Galvanized Metal roof - 16ft long. I was hoping someone here could recommend where to put the screws in the metal? I was told to put the scews every 12 inches on the raised hump area. Is this correct? Any help is appreciated.

Mitch

 

[texasjohn]

I will tell you what I believe and makes sense to me, and why.... am sure you will get other and contrary opinions.

When we built our house, I wanted a metal roof for longevity and no leak reasons. When it was put up, I was not there. When I saw it, I immediately objected to the builder that the screws were placed in the valley, not the raised part of the metal. The builder explained that he used self taping screws with a rubber grommet that pulled down tight, held the metal to the wood part of the roof, and prevented leaks.

I believe him.... my mistake.

At about 15 years, the roof began to leak... I discovered that bunches of the screws had backed out part way, thus leaving a hole in the metal in the valley where water was easily entering. I spent much time on the roof removing each screw, inserting roofing tar/caulk, reinserting screw.

This worked for 3 or 4 years when leaks again began.... I discovered that the caulk I had used had gotten hard and, again, some screws had worked their way back out.

So, again, I found all loose screws and this time used the best latex/rubber caulk I could buy and did each one.

Thats wheree things stand now. This newer caulking round seems to be lasting longer and the flexibility seems to help prevent back out.

My current belief is that ALL screws should be put on the peaks of the metal, not the valley. AND that the self taping screws with washers under them should be used, AND that a torque drill should be used to apply the screws so that you do NOT deform the metal, just pull the screw in tight ans squish the washer slightly.

This requires use of a longer screw and more care in application. I think this is what the builder wished to avoid... saving him costs and costing me much pain and time at a later date. His gain, my pain after the "builder's insurance" ran out.

Since this experience, I have had the chance to visit numerous countries in Latin America... Costa Rica, Honduras, etc. There, I noticed, they ALWAYS put their fasteners on the peak of the metal corrugations. Since they get lots of rain, I think they have a reason for doing this.

This is my experience.

I had a hard time finding the installation instructions referenced in the note below..so here is the link.

 

[Slacker]

This site has install instructions for all common metal roof types. Go to "products" and scroll down to the installation instructions.
Union Corrugating

 

[MrJimi]

And a 16 foot 2 X 6 will sag/droop/hang-down big time after a very short amount of time

 

[shvl73]

Here's another industry link: http://www.mcelroymetal.com/elements/files/Max-Rib Installation Maual.pdf

 

[khd]

I'm getting ready to install MCElroy Max Rib on my barn and will be using the stitch pattern (screw through the ribs). I never considered leaks but think aesthetically it will look much cleaner to have all the screws on the ribs vs. scattered around the panels.

Regards,
Kevin

 

[shvl73]

On average to short panels, screwing through the ribs should work ok. On long panels, expansion and contraction can cause screw movement and oval out the screw hole leading to leaks. Screwing through the flat is the preferred method. Be careful not to overdrive the screw (strip the hole), the screw will eventually work out and leak. If you happen to overdrive a screw, replace with a stitch screw and move on.

 

[Nasty135]

Mitch, I have used Fabral: Grandrib 3 on two different roof jobs for myself and though it has onlt been about 5yrs. no leaks as of yet. It was easy to work with and can be ordered cut to length, I'm sure other company's probably offer the same... The website has installation instructions as well..

Now I have "heard" that if you use the sealing nail type attachment process , they go on the peak of the rib, but if you use screws they go on the base... I can see the idea of the screw on the peak as well...

Good Luck & don't forget to wear your spyder-man shoes

 

[Dallas_Lilly]

Most metal roofs are not thick enough to require a self tapping screw. Use screws that have a sharp point to them and a rubber washer. Self taping screws will not work well when fastening material to wood, they are meant to fasten material to metal. The taping part of a self tapping screw drills to large of a hole in wood for the threads to get a good bite.

 

[EddieWalker]

I was told to put the scews every 12 inches on the raised hump area. Is this correct? Any help is appreciated.

Mitch

Mitch,

There are a few misconceptions about fastening metal roofs, and most have been mentioned here already.

First, make sure you get good quality screws with rubber gaskets designed for wood. This is extremly important!!! If you use the wrong screws, they will not hold.

When you screw them in, be sure to stop as soon as the rubber gaskets starts to bulge. NEVER over tighten them!!!! If you do, two things will happen. You will destroy the rubber gasket and it's ability to seal out water. Second, you will strip out the wood and stop the threads from holding the roof down.

There are all sorts of metal roof stypes and types, but basically there are two characteristics that seperate them. Corugated metal is has the costant up and down U without any flat surfaces. I kind of think this is what John saw in Latin America. This type of roofing is installed over a wood undermaterial that is cut to form the same pattern of the corugated metal. This is usually nailed on with the nails through the highest point of the metal. It's very common and been around for ever. It almost always leaks over time, but mostly because it was nailed and not screwed down.

Moderm metal roofing like an R panel has flat and raised parts to it (ribs). You ALWYAYS attach it to the purlins through the flat portion that is touching the purlines. You NEVER want to have any void or space between the screw head and the purlin. NEVER!!!!!!!!!

If you fasten through the ribs, you won't find the proper screws because they do not exist. Nobody does this. Next you will have to invent a spacer to fill that void to keep the metal locked to the roof. Just tightening it to the point of holding it down will gurantee failure. It will also void your warentee.

After you fasten the panels down to the purlins, you will have to fasten screw the overlap of the metal panels to each other.

There are two types of screws to use. Metal to metal and metal to wood. Be sure you get the correct ones. Both are self tapping and are needed to get through the metal. The metal to metal screws are needed for the overlap. You will only need a few of them compared to the metal to wood ones.

Be sure you know how to overlap the metal. There are two options. One is right, the other isn't. The same is true for how many screws to put into each purlin. I like to have two screws on either side of the panel and leave the middle one blank. I've seen where just one is used for each panel, but don't feel comfortable doing that myself. I've also seen where three are used, but that's usually when the purlins are over four feet apart and you need the extra strength. With your purlins at 12 inches, I'm thinking two on one purlin, then one on the next with it going back and forth. Of course, two on each purlin will work too, it's just overkill.

For the metal to metal screws on the overlap of your ribs, be sure to put them in every four feet.

Make sure you have a vent, or vents at the peak. I think the number one reason for metal roofs to sweat and create condensation is the heat rises to the peaks, but has no where to go. It forms moisture there and that water runs back down the roof. At the purlins, it drops to the floor. I've seen this in allot of metal buildings and it's always the same thing. No air movement and no peak vents.

16 feet is way too long for an unsuported 2x6 to hold up it's own weight. It will never last with a load on it of any kind. Is the 2x6 part of a truss? How is it supported?

What pitch is the roof?

I've found that clean, white soled sneakers are the best for traction. Dark soles are harder and more slipery. 4:12 is about as steep as I feel comfortable walking on without safetey gear. Any steeper, and you are working on a slide.

Be sure to start early in the morning and work on a dry roof. Morning dew will kill you, so wait for it to go away, then start. It wont take long for the metal to get too hot to stand on. It feels like the bottom of my feet are on fire after awhile and I have to get off the roof.

Get a big magnet with wheels for picking up all the screws you drop. Just run around the building with the magnet to pick them up. Kids love to do this if you have any around.

Don't try to do it all at once. Get enough screws down to hold it in place. You can always come back later to finish it off.

When doing an entire roof, sooner or later you will put a screw through the metal and not find a purlin. It happens. You can usualy put the larger metal to metal screw in the hole to seal it up, or you can fill it with a high quality caulking. I always try to use the screw to plug the hole first, but sometimes you have to caulk. Silicone might work too, but you can't spray paint over silicone. Find a matching paint for scratches and patches.

Eddie