My building has an online bulletin board where people can post ads for various types of items, including apartments they’re trying to sell or rent. It’s rather basic: just a text listing plus some contact info. But there’s one aspect to the real estate listings that I rarely see elsewhere: every listing includes the floor number that the apartment is located on.

Why don’t regular real estate ads do this more often? Even in big cities like Chicago where high-rise buildings are common, I’d say no more than 10% of the real estate ads specify which floor the apartment is on. And why does the bulletin board at my place list the info so consistently?

Perhaps our bulletin board has big, bold text on the page that you use to post a listing, reminding people to include the floor number. Or maybe people just think of it more readily when all the listings are in the same building, making the floor number a main differentiator of one apartment versus another. Regardless of the cause, the takeaway is simple: if you’re posting a real estate ad for anything that isn’t on the ground floor, be sure to specify which floor it’s on. And if you’re designing the interface for a real estate site, it’s probably a really good idea to make the floor number a required field.