I’d start by figuring out where the furniture actually touches the deck. Urban outdoor furniture often has thin metal legs, small plastic feet, or hard casters, and those are the spots that do the damage. Flip each piece over and check for rough edges, missing caps, or worn glides. Replace anything that feels sharp or loose before it digs into the boards.
Then add the right protection. For lightweight chairs and tables, outdoor-grade glides or rubber caps are usually the easiest fix. I’d avoid plain indoor felt pads for wet or gritty urban balconies because they can trap sand and wear through quickly. Look for pads made for outdoor use, and check them every few weeks. If the furniture is heavy, use wider coasters or furniture cups to spread the weight.
A small outdoor rug or interlocking deck tiles also helps a lot, especially under a bistro set or a grouping of chairs. It creates a buffer and makes it less likely that grit will grind against the deck. Just keep the rug clean and lift it occasionally so moisture doesn’t get trapped.
The biggest habit change is to stop dragging furniture. Lift it, or ask someone to help with heavier pieces. I also sweep or rinse the deck regularly because sand and small stones act like sandpaper when furniture moves over them. If you have composite decking, check the manufacturer’s advice before using certain pads or cleaners. With a little prevention, urban outdoor furniture can look good without leaving a trail of scratches.