That's a practical question I get asked surprisingly often! The honest answer isn't a single number, as it varies by bin. However, for a standard, commercially-available plastic outdoor trash can (like a 32-96 gallon wheeled model), the lid is generally designed to support only its own weight plus perhaps 5-10 pounds (2-4.5 kg) of incidental pressure, like a light bag or some leaves.
Think of it as a cover, not a shelf. Most lids are made from molded polyethylene plastic and are hollow or thinly ribbed for cost and weight efficiency. Their primary job is to keep odors in and pests out, not to bear significant loads. Placing heavy items like tools, potted plants, or a second bag of trash on top is a common cause of cracking, especially in cold weather when the plastic becomes brittle.
Factors that affect capacity include:
* Material: Thicker, UV-resistant plastic holds up better than thin, cheap plastic.
* Design: A flat, solid lid is stronger than a domed, hollow one. Lids with reinforced hinges or central supports can handle slightly more.
* Age & Weather: Sun exposure (UV degradation) and extreme temperatures weaken plastic over time, reducing its strength.
If you frequently need to place items on top, consider a bin with a flat, reinforced lid or a dedicated storage bench. For the standard bin, it's best to play it safe. Treat the lid gently, and avoid any weight that makes it visibly bend or strain. A broken lid leads to spills and pests, so when in doubt, keep it light.