[RE-wrenches] S5 Clamps

Thu Sep 18 18:54:01 PDT 2008

Hello Matt,

Your detailed postings are great. I did a some Uni-Solar standing-seam solar 
roof systems on new construction about 12 years ago when Uni-Solar was 
factory laminating the panels. Lessons learned. Shipping wooden crates of 
McElroy Medallion-Lok roofing from Michigan was way too expensive back in 
pre peel-and-stick days. Roof panel clips are pretty flimsy so use extra 
care and extra clips when installing roof panels. Fastening clips to metal 
purlins with self-tapping screws requires skill and quality control to avoid 
stripping out the screw holes. Installers should always test their mount 
fasteners by trying to rip the fasteners out of or off of the roof, wall, 
etc.

Joel

----- Original Message ----- 
From: "Matt Lafferty" <gilligan06 at gmail.com>
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
Cc: <big.oil.lies at gmail.com>
Sent: Thursday, September 18, 2008 3:23 PM
Subject: Re: [RE-wrenches] S5 Clamps

> Joel D said:  "I would be concerned about the whole roof lifting up in a
> strong wind"
>
> Me, too.  http://www.youtube.com/watch?v=IHxc8AwG5Ac  This is not a
> tornado... Not a hurricane... Just wind. And not a particularly strong 
> wind,
> either.  Helps explain why TX has built so many wind farms...
>
> I really like the S-5! in the right circumstances. I am concerned that 
> it's
> so "easy" that it can be and has been used in applications where it has 
> been
> vetted about as well as McPain's hunting mate. In nearly all evaluations
> I've done of existing S/S roofs, where the structure was actually able to
> support the added weight of an array, the weakest link has been the
> attachment of the roof skin to the building. Uplift forces at the roof
> surface (array location) are transferred to the building structure via 2
> attachements, not just 1. The "clip" has a top and a bottom. Both ends 
> must
> be evaluated. I've found more than a few that don't pass a responsible
> structural analysis "as-is"... Without solar.
>
> Older documentation from metal bldg/roof mfrs provided a psi or psf rating
> for the "top" connection... Where the clip attaches to the metal skin.
> "Snap-Click". Be sure to double-check the units... I've seen psi 
> published.
> There are 144 sq inches in a square foot... If you're looking for 35 psf 
> and
> you see 350 psi, you don't have a 10X safety factor! What was less often
> published is a rating for the attachment of the clip to the structure. 
> This
> gets really squirrely when the clip is screwed into OSB &/or plywood.
>
> Another point that I have seen engineering calcs fail (but not physical
> failures so far), is tear-thru... Where the clip is torn right over the
> screw head that holds it to the structure. This is different than
> "pull-out", where the screw pulls out of the structural member. Frankly, 
> I'm
> not convinced that the couple of times where the engineers came up with 
> this
> it could possibly happen... I don't think the top of the clip is gonna 
> hold
> on long enough to tear the bottom of the clip this way. But that's what 
> the
> guys with the fancy initials and the little round rubber stamp said...
>
> Hopefully your application will have complete published data on the system
> used and conditions found at the site. Don't forget to actually VERIFY the
> clip spacing and attachments! Again, metal over OSB/ply requires special
> attention. In these cases, I recommend taking some of it off in a few 
> areas
> to investigate if you can't otherwise prove what's in there. One of my
> favorites is the wood-truss/osb install where the original documentation 
> and
> engineering is based on (2)ea x 1-1/2 or 2" screws directly into the top
> chord of the truss at each clip with 48" spacing up the truss. From the
> ground you can see that the seams don't line up with trusses anywhere and
> you can clearly see the tip of a single screw come through the OSB by a
> whopping 1/4" in the eaves. Sooooo... You want me to believe that you "did
> it the right way" where nobody can see it, but not where it's in plain
> view?... I've been to Missourri... Try again. Oh, wait... That's not my
> favorite part! My favorite part is breaking the news to the owner that his
> roof is gonna blow off so he can't have solar on it unless we do 
> standoffs.
> And, yes, I TOTALLY appreciate that he "built it this way so he could have
> solar and no penetrations". (Just kidding folks. This is NOT my favorite
> part. These situations break my heart and tick me off to no end. Somebody
> cheated and now somebody else has to pay for it... One way or the other)
>
> Look out for roof-skins that are already coming loose from the structure. 
> In
> my experience, these situations generally occur where there are long &/or
> multiple panels between a "ridge" and an "eave". I haven't personally
> observed it in flat-slope apps, but suspect it happens on those, too. Be
> VERY cautious on steel buildings with open walls. I've seen plenty where 
> the
> skin is already flopping loose when you get there. The clips have already
> released from the skin and/or completely deformed. I've mostly seen these 
> in
> ag applications. Riding arenas, hay-barns, tool sheds, etc. A municipal 
> dump
> transfer station building, too... That one was probably the worst of all 
> in
> this regard. Here was a beautiful, long, wide-open roof that was literally
> flapping in the breeze as you walk on it. The pressure differentials on
> these buildings are magnified greatly from those of a normal "enclosed"
> structure... Positive pressure below the roof + negative above = lotsa 
> lift.
> Probably the single biggest factor that goes into causing these to fail is
> that wind is not "smooth and steady". If you are the roof on one of these
> buildings, you are being pounded continuously. Stand on or under one of
> these buildings when there is a 10 mph or greater wind and just listen to
> it... It doesn't just "creak and groan"... It "bangs and slaps".
>
> Another sign of trouble to watch for is horizontal creasing of S/S panels.
> In order for a panel to crease, it has to get bent some time... Either
> before or after it is installed. When these profiles get bent, the seams 
> get
> distorted. They don't fit like they were designed to. Since the clip 
> design
> is dependent on a perfectly shaped seam, you kinda gotta wonder if the 
> "new
> shape" is gonna hang in there when mother nature starts pulling on it...
> That dump transfer station roof had these creases all over it... Don't 
> know
> which came first, the crease or the loose roof, but at this point it 
> doesn't
> really matter, does it?
>
> I'm comfortable with the holding power of an S-5! For purposes of wind
> analysis, it's the strongest part of the attachment system. For 
> applications
> where this method is an option, right after making sure the building can
> physically support an array, the next thing I look at is the
> roof-to-structure attachments. I never kept an actual tally, but I'd
> estimate that only about 20% of the potential S-5! projects I looked at 
> over
> the years passed this phase of the evaluation without requiring
> modifications of some sort.
>
> For "smaller-ish" arrays, don't waste $ on rails. For "normal" sized,
> rectangular, shaped modules, turn 'em sideways (landscape). Figure on 
> using
> an S-5! at every seam or 24", whichever is greater, and run the math that
> way. I, personally, want a minimum safety factor of 2+ for these apps. In
> this part of the country, it is common for all-steel buildings to have 
> only
> 1 clip for every 12-14 sq ft... Horizontal purlins @ 63-66" spacing with
> vertical seams every 24 or 32"... You MIGHT get this to calc in zone 1 of 
> a
> barn with low-slope roof, 85 mph basic, cat B exposure, good screws,
> high-quality roof profile, and a strong clip... I've seen it done. But it
> doesn't get near a 2X safety factor...
>
> Keep in mind the "S-5! WARNING... The S-5! clamp is a handy gadget for a
> great many uses, but will not perform miracles." <
> http://www.s-5.com/Home/index_457.cfm >
>
> Miracles is what hammocks is made for...
>
> Matt Lafferty
> gilligan06 at gmail.com
>
>
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