Unless you're a hermit who never entertains, you've probably wished for an extra bathroom now and then. But bathroom additions require serious coin. For a moderately outfitted addition with synthetic stone or plastic laminate surfaces, figure parting with about $21,695, according to the Remodeling report. Go upscale, with finishes like premium marble or fine tile, and you can easily spend in the neighborhood of $40,710.
Either way, you get about the same return: 53 cents on the dollar. In the buyer's mind, the additional bathroom isn't worth that additional $20,000 to $40,000.