[RE-wrenches] truss loading

[Joel Davidson]

In Southern California and most other places that allow 2 layers of composition shingles (new roofing over old) inspectors will allow PV on 1 layer of shingles without structural engineering so long as you seem competent and use a store-bought mounting structure with nice installation instructions (i.e. Unirac) that the inspector can read.
  ----- Original Message ----- 
  From: Jeff Oldham 
  To: re-wrenches at lists.re-wrenches.org 
  Sent: Tuesday, October 28, 2008 4:46 PM
  Subject: Re: [RE-wrenches] truss loading


  If trying the link that Bill supplied does not fully swing the LJO over to reason try my tactic that has yet to fail me - I explain that virtually all structures built in the last 30 years or so have engineered roofs to handle both Live and Dead Loads, typically the Live Load is in excess of 12 p/s.f. and is in addition to the Dead Load. The Live Load is for temperary loads such as workers and materials. My pitch is simple; once I have placed my 3-4 p/s.f. of glass over the roof it has eliminated that area for any live loads, because we do not walk, stand or place heavy materials on our arrays. In essense I have eliminated the potential for Live Loads of >12 p/s.f. with <4p/s.f. of array. This blatant logic has yet to be balked at except in cases of some commercial projects and older buildings. Also in many jurisdictions one is allowed to put a second layer of shingles over the 1st w/o removal of the original and w/o Engineering, if this is your case and the second layer has not been installed then this argument can also work as our arrays are a fraction of the weight of most any roofing system.

  Good luck!



  -jeff o


  From the Solar, Wind and Hydro powered office of Jeff Oldham/Regenerative SOLutions



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