rail orientation on steep roof

[electrofelon]

I have a job with a steep 12/12 pitch corrugated thru fastener roof. It works out that to squeeze the max amount of PV on the roof, the modules will need to be mounted in landscape. The question is which way should the rails run? East West uses twice the rail footage, so more cost and more time, but on the other hand would make for lots of nice "stops" to stand against and put stuff against while working. Obviously with up/down orientation, I would be at t he mercy of the rib spacing, but module mounting location seems flexible enough that that would not matter. I mostly do ground mounts so I would love some input from the roof guys who have more hands on with roofs.
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[ggunn]

I have a job with a steep 12/12 pitch corrugated thru fastener roof. It works out that to squeeze the max amount of PV on the roof, the modules will need to be mounted in landscape. The question is which way should the rails run? East West uses twice the rail footage, so more cost and more time, but on the other hand would make for lots of nice "stops" to stand against and put stuff against while working. Obviously with up/down orientation, I would be at t he mercy of the rib spacing, but module mounting location seems flexible enough that that would not matter. I mostly do ground mounts so I would love some input from the roof guys who have more hands on with roofs.
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When I was doing resi systems we always ran the rail horizontally no matter what.

 

[electrofelon]

When I was doing resi systems we always ran the rail horizontally no matter what.

This is what I see 99.9% of the time. But is there any reason other than having the rails to stand against and rest stuff on during installation? Just wondering if there is some other thing I'm not considering.

 

[Zee]

Running rails horizontally is primarily due to the fact that rafters run vertically.
Portrait orientaton of panels is a result of that - just like you said- to save on rail.
Finally, for stops (AKA "scaffolding" the roof).

I would definitely run them horizontally - ESPECIALLY on a 45 degree roof!
If you are in ropes, it is not comfortable, and that will save your back.

It is much safer. Both to prevent heavy items from falling and you......
You cannot even put ANYTHING down on a steep roof with vertical rails. It is very frustrating.

Vertical rails are BRUTAL on a steep roof.

PS I also hire scaffolding for any steep roof. Up to eave. Then just install mounts in horizontal rows, and set rail as you go up the roof , stepping on each rail as you go up. Easy.
The sense of safety from scaffold and horizontal rails is worth it.

Otherwise, figure 3 times the amount of man hours on a steep job.

PSS Consider screwing in a stainless steel anchor or two at ridge and leaving it......may be useful when customer calls you to replace 3rd panel in 2nd row 10 years later.......

 

[electrofelon]

Running rails horizontally is primarily due to the fact that rafters run vertically.
Portrait orientaton of panels is a result of that - just like you said- to save on rail.
Finally, for stops (AKA "scaffolding" the roof).

I would definitely run them horizontally - ESPECIALLY on a 45 degree roof!
If you are in ropes, it is not comfortable, and that will save your back.

It is much safer. Both to prevent heavy items from falling and you......
You cannot even put ANYTHING down on a steep roof with vertical rails. It is very frustrating.

Vertical rails are BRUTAL on a steep roof.

PS I also hire scaffolding for any steep roof. Up to eave. Then just install mounts in horizontal rows, and set rail as you go up the roof , stepping on each rail as you go up. Easy.
The sense of safety from scaffold and horizontal rails is worth it.

Otherwise, figure 3 times the amount of man hours on a steep job.

PSS Consider screwing in a stainless steel anchor or two at ridge and leaving it......may be useful when customer calls you to replace 3rd panel in 2nd row 10 years later.......

Ok thanks. However I have decided to run the rails vertical. The panels have to go landscape, and despite the increased installation difficulty it will cause, it kinda works out better in a lot of ways. Ill let you know how it goes!

 

[shortcircuit2]

Vertical...as long as the engineer approves of the point loading. Around here, always horizontal with staggered mounts due to snow loads.