It's wise to consider weight limits before placing planters on your balcony. The total weight of a filled urban planter box depends on several key factors: the planter's empty weight, its size (volume), the growing medium used, moisture content, and any plants or decorations added.
A typical medium-sized resin planter (around 24 inches long) might weigh 5-10 lbs empty. When filled with standard potting soil (which weighs about 20-25 lbs per cubic foot when dry), the same planter could weigh 40-60 lbs. Add water, and the weight increases further—water weighs roughly 8.3 lbs per gallon. A large wooden or metal planter can easily exceed 100 lbs when fully prepared.
To ensure safety, first check your balcony's weight capacity, often listed in your building's guidelines or lease agreement. Distribute weight evenly and consider using lightweight materials like fiberglass, resin, or fabric pots. Using a specialized lightweight potting mix instead of dense garden soil can significantly reduce the overall load. For precise calculations, always measure your specific setup, as weights can vary considerably based on your choices.