While looking for a reclaimed piece of furniture to use, keep in mind that the average bathroom countertop is 34 to 36 inches in height. When selecting a piece, make sure that the top is strong enough to hold the sink you've chosen to drop in. It's best to have your sink template with you, if possible; you'll be able to make measurements and figure out the best place for the faucets to go. Another thing to consider is the style of the front of the vanity. If the piece you have chosen has drawers, you'll need to retrofit the drawers inside in order to have room for all the plumbing underneath. A vanity with doors instead of drawers works best.