This choice is influenced by a few things. On the exterior, we apply a top coat of premium paint after a very thick primer. One coat of each can do the trick if you stick with the same colour or just a shade different. If the colour is going to change substantially, we apply two coats of exterior paint. Unless you insist on only one application and the wood isn’t too dry, stain treatments require two coats. On occasion, we will apply two coats on the sunny side of the home and one on the interior, but we typically advise applying two. Two thin coats of paint are always used when painting over aluminium or vinyl siding.