Metas roof to wood, screw placement, which camp are you in and why?

[catfishdaddyengineering]

We did both when I worked for my uncle 20yrs ago. We screwed in the valley with standard washer screw and screwed in the ridge on joining sheets with a short "stitching" screw. This stitching screw was a self-threading fat short screw to tighten up the two sheets where they joined. We also used double-sided tape. This was for mostly commercial buildings, and we always came behind to check the washers. Any that the washer was boogered up got replaced.

 

[PILOON]

The key to fastening metal roofing through the ridges (recommended by some manufacturers) is pre-drilling...

stacking the panels and laying out the (purlin) pattern (based on measurements taken from the framing) then drilling pilot holes makes for an almost perfect looking job (appearence wise) it also makes it very easy and fast to set the screws...

Granted, the frame should be as square as possibe...the pilot holes also make it very easy to get the metal started off square and true also...(if the lapped over holes do not line up...something is not square)

When finished, the screw heads should line up diagonally arrow straight from any direction...it makes for a very sharp and professional looking installation...

For shure!
Makes for a truly professional looking job!
I plot out the first sheet using a "T" square, trial fit, and save it as my drill template for the rest.
We found that 5 sheets could be 'gang drilled' at a time but that one trick was to lock the 4 corners of the '5 sheet pile' with vise grips otherwise we would break too many drill bits.

Real pretty results!

When siding with metal, the nicest results are screwing on flats, again using the jig technique for nicest results. (INMHO)

 

[Lineman North Florida]

Tallyho8 made a good point a properly installed screw will pull the lighter gauge metal up around it instead of making a dimple therefore making it hard to leak, I've done it both ways the last barn I built for myself was a 32x60 all roofing screwed in the flat, no leaks as of yet, bottom line I believe either way will work for you, just do what your most comfortable with so you can sleep at night.

 

[alchemysa]

Might help if the OP said what profile of metal he's considering. I assumed by 'roof metal on a house' he meant corrugated. (He also said standing seam was too expensive).

 

[Arky217]

Might help if the OP said what profile of metal he's considering. I assumed by 'roof metal on a house' he meant corrugated. (He also said standing seam was too expensive).

The profile I'm considering is the 38" wide (36" coverage) 5 rib style. Ribs are 1.25" high.

I think the main problem with through fastener metal panels is the expansion/contraction of the metal due to temperature changes. I read where the length of a 40' metal roofing panel was measured at 20 degrees and again at 100 degrees. It was stated that it expanded 5/8" longer. For a 16' length (which is what I need) that would equate to 1/4". And that's with an 80 degree temperature change. (I can imagine that the temperature of the metal with the summer sun beating down on it versus it's nighttime temperature could be even a greater span, thus you would have at least a daily cycle of expansion/contraction.)

Well, with that degree of expansion/contraction, something has to give. I think it is definitely going to be pushing back and forth on the screws and over a several year period of time, it will no doubt loosen some of the screws. When that happens, I believe I would rather any loose screws be on the ribs rather than on the flats where water would certainly pour in.

Right now, I'm considering the following two options:

1) Bite the bullet and go for standing seam roofing (26ga). The cost for my roof (panels only) would be $2310.

2) Go for the through fastener panels, and get them in 8' & 8'6" lengths. This would probably reduce the thermal expansion problem and would also make it easier for me to handle (I'll have no help on the installation).
The cost of this roof (panels only, 29ga) would be $1224. ($1388 for 26ga)
With these panels, I'll fasten them closely spaced on the flats around the perimeter of the roof (where any leaks would just be through the overhang), and on the roof proper, I'll fasten them on the ribs, but only the outer, overlapping ribs. And instead of #10 screws that are usually used, I think that I would use #14 screws to get a better 'bite' in the wood. (long #14 gasketed screws are available)

 

[/pine]

In extreme temperature swings...I would be more concerned about moisture and condensation than I would about the expansion factor...

Now if something like bronze (or other dissimilar) fasteners were being used that expand at a much greater rate than the steel it might be different story...of course that would also create a possible galvanization/electrolysis problem.

 

[6thgpSF]

Arky217, just curious as what kind of underlayment do you plan on using?On my latest project I used the stuff that HomeDepot and Lowes sells that has a stickey side to it.At $80.00 a roll kinda expensive but worth it if it helps stop any leaks. russ

 

[Arky217]

Arky217, just curious as what kind of underlayment do you plan on using?On my latest project I used the stuff that HomeDepot and Lowes sells that has a stickey side to it.At $80.00 a roll kinda expensive but worth it if it helps stop any leaks. russ

Actually, I am not going to use any underlayment as per instructions of the Huber Co. that makes the sheathing I'm using.
The sheathing is 1/2" x 4' x 8' Avantech Zip system roofing panels.
After installing, the panels are taped with a thick 4" rubber membrane tape. After taping, Huber says that the roof is watertight and will withstand the weather for at least 3 months without roofing.
(They have tested their Zip panels by making a flat roof, putting several inches of standing water on the roof, and then even applying a vacuum to the underside.)
Since this is a one guy operation, that works out well for me since the roof may get multiple rains on it before I'm done.

 

[tallyho8]

It's been my understanding that the expansion of metal panels would be divided by the number and spacing of purlins and would cause each panel to very slightly bow up between purlins.

This is one reason that metal screws are used to screw the overlaps together between the purlins. So that one panel doesn't try to bow up and the one next to it try to bow down and create a space in the overlap.

If you are using 16' long panels with 4' between purlins and anticipate an expansion of 1/4" then that expansion is divided between the 4 spaces between the 5 purlins and each 4' length will only bow up 1/16" which is not even noticeable.

I haven't noticed the expansion and contraction loosening the screws in the metal roofs in our hot Louisiana sun. Of course I always use 1 1/2" screws going into 2X purlins. I never use or recommend using 1xs for purlins.

 

[tommu56]

As for laying the screw holes out I make a story pole and just put a marker dot were screw is to go that way if you got an oops no harm just move screw.

If panel is a little out of kilter you can tweak it mount on lapped panel see were you need to move with a level screw other side plumb the do the field making the ridges a little higher and tighter you can get 3/8 or so per panel to get them going straight.

tom