couplers are fugly, and typically, the weld material (wire) is stronger than the steel its holding together. i like to butt weld, if the weld is supporting weight, i'll put a slug inside. if its a show-piece, i'll grind it down and make it disappear. for the most part, once finished with paint or powder or whatever, they're no big deal. the expanded metal will be on top of the floor supports and the installed height, at it lowest point will be just off the roof, 1/8-1/4". for washing concerns, a pressure or power washer will blow stuff out of any nooks and crannies pretty well. but if you choose, a big piece of vinyl would be a simple way to go.