Installing L-feet on metal roof?

[DayStar]

Hi, i had to install an array on a metal roof (corrugated) and the problem that i ran into was that in order to mount a few of the L-feet i had to use a hammer to flatten down the ridge (about 1" high) that runs down the metal sheeting. The ridge just happen to be directly above the desired truss and moving to the truss on either side was not an option at the time so flattening the area where the L-foot needed to be was the solution to a well supported mount.
I was successful in attaching the L-foot however it didnt seem that it was in good craftsmanship to bang out the ridge with a hammer and i would hate to have to do it again.
I am looking for suggestions or alternatives to doing it this way.

Thanks.

I can include a photo if anyone needs a visual aid.

[Jason]

Daystar,

Welcome to Solar Panel Talk and thanks for joining.

I'd attach the photo if you wouldn't mind...it may help with getting a reply.

Thanks!

[DayStar]

Thanks Jason, a photo definitely makes it easier to understand!
This was the worst one because the metal split where the hole was. I had to rough up the surrounding area with sandpaper and use plenty of sealant before i felt confidant that it would not leak.

[Mike90250]

Ouch ! are those brackets even designed for that kind of roof ?

Do the 2 bolts on the left in your photo have any sealant to keep from leaking ?

[DayStar]

The 'bracket' is an L-foot that is quite common in roof mounted PV systems and is meant to be used on flat surfaces, well composite shingles at least. To be honest, i just sent an email to the manufacturer to be sure. I'll post the reply.

The roofing screws to the left have gaskets under the washers.

Other than L-feet, I'm not familiar with any specific product that is for mounting to a corrugated metal roof. If anybody knows of one, or alternate way, then please share it!

Has anyone else installed on a roof like this one? How did you do it or see it done?

[Johnny Electriglide]

Metal roofs

Metal roofs I have done are mounted to 2x4s going 90* to the rafters and nailed or screwed to them well, at 2' or 16" OC. Sound board is laid first, and the overlap of each metal section and other contact points are screwed down with rubber washers. Any panel mounting hardware should be put at those contact points, even removing and replacing the existing screws. Smashing the roofing like that is a big mistake.
If the metal roof was mounted directly on OSB(or soundboard on OSB), then everywhere on the low corrugation is a contact point where shorter lags would hold, especially with a 22.5" block under(on 2'OC truss/rafter systems).
The roofing system should have been examined carefully beforehand to determine how it was mounted.

[ClearAir]

The best way to install "L" feet on a corregated metal roof is to first install Uni-Strut laterally across the ridges. The steel Uni-Strut can be attached to the roof with properly sized lag-screws at multiple points AND the screws should pass through the OSB and securly go into the rafters. The size and depth of penetration of the screws needs to be engineered based on wind loading and the species of the wood rafters.

The Uni-Strut allows you to attach the L-feet to it, circumventing the problem of the feet not lining up with the rafters.

A good sealant that I have had good success with is called: Pro Flex made by www.geocelUSA.com This is much better than silicone caulk which fails due to the thermal expansion and contraction of the metal roof.

[DayStar]

Thank god for clean air!!!

You know what, i thought about using unistrut, after the fact of course! I have used it before when mounting to vertical walls that were uneven and never even thought about it for on a roof.

Thanks also to johnny,

If the metal roof was mounted directly on OSB(or soundboard on OSB), then everywhere on the low corrugation is a contact point where shorter lags would hold, especially with a 22.5" block under(on 2'OC truss/rafter systems).

I have often considered using a block of wood under the roof deck where a rafter may not be accessible. Although i haven't tried this yet,
Has anyone? Do's, Don'ts???
Bolting an array mounting bracket directly to the roof deck alone should never be done, there is not enough pull out strength in the deck itself. You need to be certain that your lag bolts are mounted directly into the rafters, otherwise the next wind day may leave you without a roof over your head.

[Mike90250]

I've seen, in the big box stores, "lath strips with ridges sawn in" that are for mounting corrugated roof panels. They go under the panel, and give a 100% solid backing to nail
or screw, at the high spots (less leakage potential).

[mattm]

Thread resurrection

Thanks for the thread! I'm just about to do an installation on the same type of roof with the same L-feet. In different posts people recommend:

1. Removing existing screws from raised corrugated parts and using those holes to lag to the rafters.

2. Drilling new holes to fasten to the 2x4 cross members in the low sections of the roof.

Does anyone have any positive/negative experiences with either?

I know there are less odds of leaking when penetrating the raised sections, but the L-feet will stick out over the edges and distribute weight over a smaller area.

Also, does anyone recommend any kind of gasket under the L-feet on steel roofs? It appears that the metal-to-metal connection could cause some wear or easily conduct any vibration noise to the roof.

Thanks!

[mattm]

CleanAir:

Roughly how many penetrations can you seal per tube of Pro-Flex?

Thanks!

[Mike90250]

Look for clamps, that grip the standing seam, and clamp on, no holes.
example:

http://www.s-5.com/clamps/applications/Index.cfm?Entity=4&Department=23&Dept_Order=2&This_TopicOrder=2&This_SubtopicOrder=1#1

[mattm]

Unfortunately it has a trapezoidal profile that won't work with the S-5 clamps.

[Mike90250]

Unfortunately it has a trapezoidal profile that won't work with the S-5 clamps.

Darn, there goes the roof warranty. Maybe someone else has ideas?

[russ]

İ am afraid that if a contractor did that to my new metal roof he should be running for the hills.

Talk to an architect or civil engineer doing house design. They should be able to come up with a bridging solution of some sort that does not include damaging the roof.

From the photo - Even after mashing up the roof section there still is not a good flat area for the L foot to sit on and make a good connection. Nothing positive was accomplished.