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Gravel Foundation for Pre-Cast Electrical Shed in Southern California

Gravel Foundation for Pre-Cast Electrical Shed in Southern California

Gravel Foundation for Pre-Cast Electrical Shed in Southern California

(OP)
Hi All -

I'm managing the construction of an electrical upgrades project, which will install a small electrical shed (12'-L x 16'-W x 8'-H).  The electrical shed is specified as a pre-cast concrete building "capable of withstanding the effects of earthquake motions determined according to CBC 2010" and to "bear fully on a crushed stone base...14" thick or down to firm subgrade".  A concrete foundation is not clearly specified.  Location is Southern California (seismic zone 4).  

My engineer (from Arizona) contends that the specific manufacturer identified in the specifications produces a pre-cast concrete building that can be placed on a gravel foundation while complying with required codes.  The contractor says that all manufacturers that he contacted (including the manufacturer specified) require a concrete foundation beneath the pre-cast structure in Southern CA.  I don't know who to believe, and we are at a stand still.  Have contacted the manufacturer directly who does not directly answer my questions, using qualifiers like "usually" when responding (e.g. "Our buildings come with a post tensioned floor system so that all is required is a compacted site USUALLY with stone or base material".)

Can anyone shed any light on my quandary?  Is it possible to install a pre-cast building without an additional concrete foundation in Southern California?  

Sincerely,

AH

RE: Gravel Foundation for Pre-Cast Electrical Shed in Southern California

Sure it can be done.  But after a "good" seismic event you may find it 10' away or it may have moved up and down a foot or two and broken all the connections going to it.

Build a foundation.

RE: Gravel Foundation for Pre-Cast Electrical Shed in Southern California

MTE has it correct, the building might withstand the loading but it will definitely move. In fact, anything not firmly anchored down will move. Code compliance in SoCal requires that buildings have anchors to the foundation - how can you anchor to gravel?

RE: Gravel Foundation for Pre-Cast Electrical Shed in Southern California

I also agree with MTE and am in a high seismic area, but not SC.

Build the concrete foundation.

Mike McCann
MMC Engineering

 

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