How to Trim a Flush Door
- 1). Measure the inside horizontal top edge of the door opening, from corner to corner. Transfer the measurement to a strip of flat trim, with two marks on the bottom edge and the measured span between them.
- 2). Lay the trim face up on a miter saw, with the marked bottom side facing the blade. Position the trim so one of the two marks is directly under the blade. Swivel the blade to 45 degrees, pointing outward, away from the measured span. Make the cut.
- 3). Slide the trim so the other mark is under the blade. Swivel the blade so it is pointing in the other direction, which will again be pointing away from the measured span. Make the cut.
- 4). Hold the trim along the horizontal top edge of the doorway, with the bottom of the trim lined up with the edge of the opening and the two mitered angles flaring up and out at the two corners.
- 5). Shoot trim nails every 10 to 12 inches along the top and bottom edges of the trim to get it secured.
- 6). Measure and cut the side pieces in the same manner, but miter only the upward-facing ends. For the downward-facing ends, turn the saw to 90 degrees, cutting the boards straight across.
- 7). Set the side pieces in place with your trim nail gun, with the upward-facing miters on the side boards butted to the miters at the two ends of the top board, marking the two top corners. The straight-cut bottom ends of the side pieces should sit on the floor.
- 8). Run a smooth bead of caulk around the perimeter of the trim, where it meets the door casing and the wall.
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