Rooftop Units in California
Rooftop Units in California
(OP)
Does anybody know where the 2010 CBC (or 2009 IBC for that matter) specifies the minimum weight of a rooftop that needs to be analyzed by an engineer? I seem to remember 400 lbs. being the cutoff that requies an analysis, but just want to find the specific section. Thanks.






RE: Rooftop Units in California
400 lbs is correct.
RE: Rooftop Units in California
RE: Rooftop Units in California
RE: Rooftop Units in California
Chapter 34 of the CBC gives an exemption from checking gravity loading of the existing structure if the increased loading does not increase the internal forces of the supporting members by more than 5%. Depending on your roof framing / support of the unit this may or may not be true.
RE: Rooftop Units in California
RE: Rooftop Units in California
If this is a totally new weight, unless you have the original structural calcs for the roof that specifically allosed for 1 to 2 psf over the entire roof for Mechanical units/piping, etc, and the 2 psf for the concerned area of framing is greater than the weight of the unit, you should check the framing. At the least, anyway, I would check the joists under the unit that span to any purlins.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com