rail orientation on steep roof

electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
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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electrofelon said:
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.
 
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.......
 
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Zee said:
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.......
Click to expand...
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!
 
The typical through fastener steel roofs I see often have 2x4 furring laid flat horizontally every 2 feet or so, with the visible screw heads showing where they are. If that is what you have, then it fits very well with running the rails vertically.
Even with the rails running vertically, I put 12 to 16 foot 2x4 planks under the rails, against the mounts, for foot-holds, and slide them out as the array build progresses. Photo below.
1726533076317.jpeg
 
solarken said:
The typical through fastener steel roofs I see often have 2x4 furring laid flat horizontally every 2 feet or so, with the visible screw heads showing where they are. If that is what you have, then it fits very well with running the rails vertically.
Even with the rails running vertically, I put 12 to 16 foot 2x4 planks under the rails, against the mounts, for foot-holds, and slide them out as the array build progresses. Photo below.
View attachment 2573443
Click to expand...
Wood on a rooftop exposed to rainwater? Isn't rot a concern?
 
wwhitney said:
Did you not read the part about "slide them out as the array build progresses"?

Cheers, Wayne
Click to expand...
Yeah, I missed that. Good. :D

If the attachments are S-5s I would be a little concerned about the structural integrity with all the attachments for a rail on the same seam; when the rails are run horizontally you can alternate seams to spread the load.
 
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ggunn said:
Yeah, I missed that. Good. :D

If the attachments are S-5s I would be a little concerned about the structural integrity with all the attachments for a rail on the same seam; when the rails are run horizontally you can alternate seams to spread the load.
Click to expand...
It also looks better when all the clamps are at the same points on the modules.
 
ggunn said:
If the attachments are S-5s I would be a little concerned about the structural integrity with all the attachments for a rail on the same seam; when the rails are run horizontally you can alternate seams to spread the load.
Click to expand...
OK, but both the OP and the picture are about through fastener metal roofs, not standing seam metal roofs.

Cheers, Wayne
 
wwhitney said:
OK, but both the OP and the picture are about through fastener metal roofs, not standing seam metal roofs.

Cheers, Wayne
Click to expand...
For metal roofs without standing seams we usually laid down unistrut vertically, attached through the membrane to the underlying purlins, with the rails run horizontally attached to the unistrut.
 
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Related: Ok I just discovered this and it's super annoying and confusing. Iron ridge uses "portrait " and "landscape" terms in relation to how the rails are run. So if I have rails running north-south/vertical, and the panels with the long dimension east-west, they are calling that portrait. Is that the most ridiculous thing in the world you've ever heard of or is that what everybody does? I always used portrait and landscape as absolute, regardless of what the rails or anything else were doing 😡
 
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electrofelon said:
Related: Ok I just discovered this and it's super annoying and confusing. Iron ridge uses "portrait " and "landscape" terms in relation to how the rails are run. So if I have rails running north-south/vertical, and the panels with the long dimension east-west, they are calling that portrait. Is that the most ridiculous thing in the world you've ever heard of or is that what everybody does? I always used portrait and landscape as absolute, regardless of what the rails or anything else were doing 😡
Click to expand...
It makes sense to me. Stress on the modules and rails depends on how the modules are oriented relative to the rails.
 
ggunn said:
If the attachments are S-5s I would be a little concerned about the structural integrity with all the attachments for a rail on the same seam; when the rails are run horizontally you can alternate seams to spread the load.
Click to expand...

ggunn said:
It also looks better when all the clamps are at the same points on the modules.
Click to expand...
For standing seam I always run rails horizontally, I agree it would never be a good idea to attach a length of rail to one seam. This OP was for thru fastener steel roof.

For thru fastener, in the photo I attached, the load is spread across multiple underlying 2x4 strapping/deck. And the spacing on the vertical run rails is pretty equal so that the clamps are close to being the same relative on all the modules. This was done by by flipping the L-foot 180 degrees or straddling a different rib as needed to maintain equal spacing.

If I were to run the rails horizontally on this job, a rail would have been attached to a single 2x4 strapping member, and the spacing of rails could only be every 2 feet or every 4 feet, since that was the strapping spacing. So horizontal rails would not have worked.
 
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solarken said:
For standing seam I always run rails horizontally, I agree it would never be a good idea to attach a length of rail to one seam. This OP was for thru fastener steel roof.

For thru fastener, in the photo I attached, the load is spread across multiple underlying 2x4 strapping/deck. And the spacing on the vertical run rails is pretty equal so that the clamps are close to being the same relative on all the modules. This was done by by flipping the L-foot 180 degrees or straddling a different rib as needed to maintain equal spacing.

If I were to run the rails horizontally on this job, a rail would have been attached to a single 2x4 strapping member, and the spacing of rails could only be every 2 feet or every 4 feet, since that was the strapping spacing. So horizontal rails would not have worked.
Click to expand...
As I said, when we encountered a metal roof that had no seams we ran vertical unistrut attached to every purlin spaced at the optimum rail span with rails run horizontally, attached with T nuts and L feet to the unistrut. Our structural engineer recommended this as more structurally sound than attaching L feet through the membrane to the purlins. Sometimes we had both portrait and landscape rows in a single array, which was simple since we could space the rails however we wanted. Of course it added to the dead load but that was virtually never a problem.

YMMV.
 
ggunn said:
It also looks better when all the clamps are at the same points on the modules.
Click to expand...
Isn't it hard to see though from ground?
ggunn said:
For metal roofs without standing seams we usually laid down unistrut vertically, attached through the membrane to the underlying purlins, with the rails run horizontally attached to the unistrut.
Click to expand...
Upside down uni strut? That is a good solution to straddle the little wave peak on the corrugated metal roof and keep it from crushing.

The last photo shows special mounts for corrugated. Seems fine too.
ggunn said:
It makes sense to me. Stress on the modules and rails depends on how the modules are oriented relative to the rails.
Click to expand...
Portrait and landscape are terms used to describe aspect ratios of 2 sides, as in paintings - not directions.
Makes little sense for rails.
Makes sense for rectangles , e.g panels.

Even N-S and E-W are not ideal...... if you have a west facing roof, for example.

Heck, sideways and up-down would be more clear.
Or the usual horizontal and vertical.

Are you sure IR uses these terms???
 
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ggunn said:
It makes sense to me. Stress on the modules and rails depends on how the modules are oriented relative to the rails.
Click to expand...
Of course, but IMO another term should be used like modules parallel or perpendicular to rails. I think almost everybody, including myself uses the term portrait and landscape to indicate how something is oriented when you are looking at it. Is this a solar thing where solar people use it differently than everyone else? It's fine if it is, I am just curious and for future reference if in the context of solar portrait landscape are used differently.
 
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I have never referred to a rail as portrait! Just panels. Like a portrait of a head vs a landscape painting.
 
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