How to Install Case Molding on a Doorway Opening

Adding case molding to a doorway opening serves aesthetic and structural purposes. A casing helps secure the door frame to the wall. In fact, without a case molding, a door might become misaligned without such support. Additionally, case moldings hide imperfections of a doorway area. For example, if a wall's thickness is unequal, applying a case molding can easily solve this problem. With a little bit of time and the proper tools, installing case molding can be uncomplicated.

Step 1

Measure and pre-cut all of the casing pieces that need to be applied to the door opening with the carbide finishing blade.

Step 2

Cut the longer lengths of the casing pieces before the successively shorter pieces with the carbide finishing blade, so the casing material is used most effectively. For a better fit for polyurethane molding, Burton Mouldings advises to cut all of the casing pieces 1/8 inch longer than the needed measurement and applying the casing end pieces onto the wall first and the middle pieces last.

Step 3

Place the cut pieces against the wall proximal to their desired locations. For polyurethane case molding, always apply a continuous line of polyurethane adhesive on the wall before finally adhering the casing. Nail the casing pieces into place with a 1 1/2-inch nail. Nail both sides of each casing with a nail--one into the door frame, and one on the other side through the drywall into the rough framing. The nails must be applied within an inch of the ends of the casing, but not too close as to risk cracking the casing. According to Burton Mouldings, a lot of carpenters apply an extra small nail through the top corner of the casing, which is beneficial if done without cracking the casing.

Step 4

Glue the corners of the casings. White glue, or PVA glue for poly vinyl products, is the best for casing, says Burton Mouldings.

Step 5

Fill the open spaces, or joints, with a paintable siliconized latex caulking. Fill any empty nail holes with a lightweight auto body filler or a lightweight gypsum filler. Two or three coats is typically enough. Finish the joints with care and effort, as they are near eye level and easily seen. Wipe any extra filler or caulking away with a damp cloth.

Step 6

Sand the surfaces of the moldings. Be careful not to sand too much, as this might remove the protective layer. Sanding too much might also result in having to apply filler and sand all over again.

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