Every so often I have to install a vanity top between two out-of-square walls. If the opening is wider in front, it’s not a problem because I can slide the top in easily. But if the backside is wider than the opening, it can be tough to install the top and maintain a tight fit—there should be no more than a 1/8-in. gap between the top and the wall.
In a case like this, I bevel the countertop along the bottom edge of one side, as shown in the drawing. Next I lean a strip of aluminum roll-flashing against the wall on the side where the beveled edge will rest. The flashing protects the drywall as I place the top on its base, using a little persuasion. To finish up, I pull out the flashing and caulk the edges.
—Rick Morgan, Manchester, NH
Edited and illustrated by Charles Miller
From Fine Homebuilding #68