[RE-wrenches] Racking System - Identification Help

[Dave Click]

Jason, thanks for the comment! I agree that systems could connect to 
just sheathing and stay on the roof- I think Zilla has a product that 
does this too. My concern about wind resistance stems from the fact that 
there appeared to be an engineer's stamp on the Unirac calcs with lag 
screws and then something completely different was installed in the 
field. It's likely that this installer has used this same mounting 
system in windier coastal areas so hopefully their fastener selection 
had some informed analysis... I didn't see any, though.

And to be clear, I'm not looking to overrule another PE if it is in fact 
an engineered system and it's just that the wrong set of plans got 
submitted to the building department.

DKC



On 2014/6/3, 10:12, Jason Szumlanski wrote:
> Dave,
>
> I can't identify your hardware, but I just wanted to comment on your 
> comment about hitting rafters. There are products out there that can 
> obtain the requisite load ratings without connecting directly to 
> structural members. We have had systems engineered and permitted using 
> Ecofasten products on low-slope roofs that fasten only to wood 
> sheathing or metal roof materials in 170 mph zones in Florida (ASCE 
> 7-10, FBC 2010). I'm not an engineer, but I've been told if there is 
> adequate data on pull-out and shear, you can use that data to properly 
> design a system without hitting rafters with the right number of 
> attachment points. I don't like the looks of what you pictured, but 
> it's plausible that it was an engineered system design. The permit 
> drawings not matching... that is another story...
>
> If, for example, each of the six fasteners provide 100 pounds of 
> pullout strength with a safety factor, that would be good for 12 sq ft 
> at 50 spf uplift per attachment. 250 fasteners would be good for about 
> 5kW of solar.
>
> Jason Szumlanski
>
> Fafco Solar
>
>
> On Tue, Jun 3, 2014 at 9:06 AM, Dave Click <daveclick at fsec.ucf.edu 
> <mailto:daveclick at fsec.ucf.edu>> wrote:
>
>     Hi all,
>
>     Anyone know what this racking system is? The permit drawings say
>     Unirac with lag screws and Eco-Fasten flashings, which this pretty
>     clearly isn't. I'd never seen this before, and I imagine this wind
>     resistance is not quite the 140 mph that the installer claims it
>     is. Of the ~250 wood screws holding this system down into the
>     roof, I think six of them accidentally hit rafters.
>
>     Thanks!
>     Dave
>
>
>
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