Inside Crown Corners
Coping crown molding is more than blindly following tradition. Understand the benefits and learn how to cope joints the right way.
Synopsis: On Tucker Windover’s first day on a finish-carpentry crew, he decided to buck tradition and miter some inside crown molding corners instead of coping them. He quickly learned that some traditions are worth keeping, and in this article he describes the advantages coped corners have over mitered ones: They remain tight even as the wood expands and contracts, they fit well in rooms with minor imperfections, they are more adjustable, and they are more forgiving. He also provides step-by-step instructions for the entire process: mitering the stock, coping the cut, testing the fit, and installing the crown. In a sidebar, finish carpenter Chris Whalen, who has been installing mitered crown for 20 years, provides a contrary view.
I can still remember my first day on a finish-carpentry crew. I spent most of my time keeping one eye on the lead carpenter, trying to pick up as many new tricks as I could. I watched him cope and fit a couple of pieces of crown molding. His movements were fluid. His process looked easy. But I didn’t quite understand why we had to complicate a joint that could be made with two simple miters. I asked if it would be OK to miter the corners instead of coping them, and the lead said, “Go for it—if you can make it look right and convince me that it will stay that way.” So I attempted to do it the easy way, or what I thought would be the easy way. In truth, I didn’t make it through a single room before turning to a coping saw.
I’ve learned a lot since then, and in my opinion, a coped joint is preferable to a miter in several ways. Due to wood movement, miters tend to open at the short point or the long point. A coped corner stays tight as each piece of trim expands and contracts in sync. A coped joint also fits well when installed in a room with minor imperfections, such as one with corners that are out of square or ceilings and walls that are less than straight, level, and plumb. The smallest bump of joint compound can throw a mitered corner out of proper alignment.
A coped joint is also more adjustable. If there is a gap in the joint, you often need only to pry the other end of the trim to squeeze the joint tight. Finally, the coped joint is much more forgiving. This makes it a faster joint to make because there is less fussing over the fit. If a piece of trim is cut slightly short, say by 1 ⁄8 in., the gap is covered by the subsequent piece of coped trim. When you’re mitering a corner, any error in length will be revealed.
Still, the coped joint has limitations. Certain crown profiles can’t be coped. In these instances, I create a hybrid joint by coping what’s copable and mitering what’s not. When working with medium-density-fiberboard (MDF) trim, I miter the inside corners instead of coping them. MDF trim is more stable than wood, but when coped, its edges become too fragile. I miter crown when installing it on kitchen cabinets that I know to be straight, level, and square. Also, I find that when preassembling crown for a column or a fireplace mantel, mitering works best.
Some people believe that coping is difficult or time-consuming. I can assure you that with a little practice, coping becomes as easy and as fast as tying your shoes.
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