[RE-wrenches] Roof Loading request for help

[Joel Davidson]

Allan,
In most of California (seismic zone 4) residential PV systems with solar arrays weighing less than 4 lb/ft2 do not require structural engineering if the roof has one layer of composition shingles. The reasoning is that roofs are allowed 2 layers of shingles (old set and re-roof set) and a layer of shingles weighs 4 lb/ft2 so 1 shingle layer and 1 solar array weighing less than 4 lb/ft2 is within the dead weight load limit. Hope this helps.
Joel Davidson
  ----- Original Message ----- 
  From: Allan Sindelar 
  To: 'RE-wrenches' 
  Sent: Tuesday, July 07, 2009 5:26 PM
  Subject: [RE-wrenches] Roof Loading request for help


  Wrenches,

  We are currently facing a city permitting bureaucracy that has recently discovered solar - that is, suddenly each department in the permitting and plan review departments is coming up with standards for PV systems. Some of the standards, of course, make no sense. 

   

  PV systems typically add about three pounds per square foot to the loading on a roof. We are facing a city requirement for structural engineering work for standard roof attachment if the mounting approach is to make penetrations into the roof structure. This is a typical requirement that will only add considerable cost to each PV system, and we're looking to have our ammunition to fight this well stocked in advance. Specifically, are building authorities in other jurisdictions requiring structural engineering work for this type of roof attachment?

   

  Thanks 

  Allan

   

  Allan Sindelar

  Allan at positiveenergysolar.com

  NABCEP Certified Photovoltaic Installer

  EE98J Journeyman Electrician

  Positive Energy, Inc.

  3201 Calle Marie

  Santa Fe, New Mexico 87507

  505 424-1112

  www.positiveenergysolar.com

   



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