I am adding a "laundry closet" in my remodel. The width dimension is easy to determine. What about the depth? I checked with an appliance salesman who said 35" min but recommended 37". Any suggestions on the correct size or where to find it?

Washers and dryers are typically 2'-4" in depth, but you need a few inches behind them for hoses and ducts. I would think that 2'-8" would be about the minimum depth, and that means that whatever doors you might have would alomst touch the fronts of the washer and dryer, so any more than that is a plus. That's 32 inches minimum, so you got good advice. Go with it.