When warehouse cages are stacked, the very bottom cage bears the total weight of all the cages and cargo above it; this is the base load. Many people look only at the rated load of a single cage and ignore the cumulative effect of stacking, which is the most common cause of overload on site.
The formula is straightforward: total load on the bottom cage = (stacking levels − 1) × (cargo weight per cage + self-weight of one cage). For example, a standard cage with a 1000kg rated load and about 40kg self-weight stacked 4 high means the bottom cage actually carries 3×(1000+40)=3120kg—far beyond the 1000kg marked on the cage.
Some ask: isn't the rated load on the cage for a single cage? Correct. The rated load is the safe load when a single cage is uniformly loaded. When stacked, the bottom cage transfers force through its stacking feet and posts, and its structural strength far exceeds the side-mesh load capacity. That is why reputable manufacturers separately specify the stacking load or the number of allowable stacking levels.
When selecting cages, first decide the most common stacking level and work backward to determine the required bottom-cage strength. For example, 3 levels with 800kg cargo each means the bottom cage carries 2×(800+40)=1680kg, which calls for a medium-to-heavy cage with wire diameter above 5mm and post wall thickness no less than 1.5mm. When purchasing, ask the manufacturer directly for the stacking-load parameters.
For acceptance, a simple check works: stack fully to the design level, leave it for 24 hours, then inspect whether the bottom cage's posts bend, whether the stacking feet sink, and whether the mesh bulges. Nanjing Tongnuo Warehouse Equipment Manufacturing Co., Ltd. calculates the base load based on actual stacking conditions and runs stacking tests before delivery.