[RE-wrenches] The perfect solar ready roof

[R Ray Walters]

I agree with Phil's always excellent posts, except for the quote below.

> On Oct 21, 2010, at 9:29 PM, Phil Undercuffler wrote:
> 
>>  risk splitting the top chord of the beam.  If you split that, I would immediately stop what you're doing and consult with the I-beam manufacturer.  Big liability moment there.
>> 


Damaging the bottom chord would be a different matter, but once the roof decking is attached to the top chord, it serves to distribute the compressive loads along with the top chord.
Basically the roof decking acts as a huge top chord for the I beam, and therefore any point loading problems caused by lag or nail damage, are distributed around the spot by the decking.
I agree you don't want a design that depends on this principle alone, on the other hand, its not like the place is about to fall down. 
I definitely wouldn't go as far as to call it a "Big liability moment". Think about your average roofing crew with a big air nailer, attaching the decking. They damage the top chord all the time, but its engineered into the design to handle that damage. 

R. Walters
ray at solarray.com
Solar Engineer

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