Crown Moulding and Ceiling Movement

Here are some tips on installing crown so that it will keep looking good despite seasonal moisture-related movement of the house structure. December 26, 2007

We have been having issues with our millwork crown pulling away from the ceiling after installation. We realize there is expansion and contraction of both the home and the millwork. Any suggestions for how to reduce the gap that is caused during climatic changes?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor P:
One of the culprits that I have seen the most, at least in the Northwest, is with houses built with very long ceiling trusses. In the winter, the house is heated and the heat rises and stays up against the flat ceiling. This causes the truss lower chord to shrink and contract in length, causing the ceiling to lift. It is most noticeable in the center of the truss. I have seen pull up as much as 3/8 of an inch when the trusses are 50 to 60 ft long. Since the walls are not connected to the trusses, separation occurs. The sheetrock will pull up and flex a bit, but crown moulding does not. You get gaps. You will notice them more in the winter. How do you deal with it? I have never been able to figure out a foolproof way, probably because I do not install anymore. I would be interested in hearing what the seasoned pros do.

From contributor J:
About a year ago I started using Liquid Nails on my crown molding installs. I don't do them very often, but have had the same problems of cracks showing up over time. The test subject for me is my own house. So far the crown I put in the bedroom two years ago has a 1/16" gap around the perimeter of the ceiling. Really drives me nuts whenever I look at it. The crown I put in the dining room last year with the adhesive still looks good halfway through the heating season. I would wait another year before swearing by it, but so far so good! Of course this just helps for the shrinking crown itself. If you have 3/8" of separation from the ceiling moving, I don't know what will help that.

From contributor R:
There are two ways I know of to avoid truss lift caused cracks. First, insist the drywaller doesn't use fasteners within 18" or more if possible of the wall - just let the edge rest on the wall's drywall. This way the truss can go up and down, but the ceiling edge won't move as much. Second, use two-part moldings as is done with wood flooring where the base is nailed to the wall and the shoe is nailed to the floor. A small molding is glued to the ceiling, and the larger molding is attached to the cabinet. The large molding needs a flat large enough to hide any movement. But don't paint it in place. This works on unlevel installs also.

From contributor S:
Two part moulding... Clever! I wonder if (for paint grade) using wall angle from acoustical lay-in ceilings would look too tacky? They have a fine line version that is like 1/2 x 15/16. Let the 1/2 leg stick down, maybe? And/or run a 1/2x1/2 square stock around the top of the crown attached to the lid for stain grade.

From contributor W:
That's a tough question. You can only make sure that the moldings have acclimated to the environment they will be installed in. But that environment, and the materials within it, will inevitably change to varying degrees depending on the part of the country or the homeowner's climate preference. I know a contractor who was working on a home addition last summer. The house had no AC (homeowner's preference) and they were installing wainscot paneling. The summers get very humid around here (Omaha) and I can only imagine what it looks like now. This movement may be a problem beyond your control. I've never tried it, but the two-piece molding sounds like a good idea.