California Labor Code
Sec. § 7603

The maximum weight of materials stored on building floors or load-carrying platforms, except those built directly on the ground, shall not exceed their safe carrying capacity.
Material, when stored, shall be piled, stacked, or racked in a manner designed to prevent it from tipping, falling, collapsing, rolling or spreading. Racks, bins, planks, sleepers, bars, strips, blocks, sheets, shall be used when necessary to make the piles stable.
Last accessed
Jun. 6, 2016