How to Install 1X4 Interior Trim
- 1). Measure across the upper span of the window opening, from one corner to the opposite corner.
- 2). Transfer the measurement to a length of 1-by-4 trim, putting two marks along the top of the trim with space beyond each.
- 3). Lay the trim face up on your miter saw, with the top edge facing the saw's back rail. Put one of the marks directly under the blade. Swivel the blade to 45 degrees facing inward, toward the measured span of the trim. Cut it.
- 4). Slide the trim so the other mark is under the blade. Swivel the blade to 45 degrees pointing inward, which will be in the opposite direction as previously (since you're working from the opposite end of the trim). Cut it.
- 5). Hold the trim up to the top of the window, so the trim's lower edge is even with the inner edge of the casing. The mitered ends of the board should start at the corners and rise out and up from those positions. Secure the piece with your trim nailer, driving nails every 10 to 12 inches along the upper and lower edges.
- 6). Repeat the process for the remaining three pieces of trim. Install them with the mitered cuts pressing against each other at the corners.
- 7). Run a bead of caulk all around the trim's outer and inner borders.
