I have three different shelving units, one in the garage that is similar though more heavy-duty than what's shown. Those shelves are 4' W, 6' H, and 2' deep. I have three units and each unit will hold many hundreds pounds of weight. In one greenhouse, I use shelving that came with the greenhouse, and it is also very heavy-duty construction. Those shelves are 12' W and 2' deep on the bottom and middle shelves and 12" deep on the top shelf. The third shelving was purchased from Lowe's, and all these are 10' W and 2' deep on the bottom and middle shelves and 12" deep on the third (top) shelf. I used the 12" deep shelves to afford more light onto that bottom and middle shelves. They are lighter duty than the other two shelving units but were much less expensive.
The heavy-duty shelving will last a life-time and the Lowe's shelving, since it is in constant dampness, will probably last 10 years, as long as I re-paint it every 2-3 years to keep rust at bay.
