Home & Garden Architecture

How to Install Doorway Trim

By Home & Garden Last updated Wednesday, May/08/2024

Preparation

1). Designate the placement of each piece of trim by marking with the carpenter's pencil an R on the back of one, an L on the back of another and a T on the back of the third. The trim marked R will serve as the right side trim, and the trim marked L will serve as the left side. The trim marked T will serve as the top.
2). Measure the trims marked L and R to match the height of your door, plus the 2-inch width of the trim marked T. For instance, if your door measures 72 inches, you need to measure each section to 74 inches to accommodate the total height of the door plus the width of the top trim.
3). Set the radial arm saw's angle to 45 degrees by withdrawing (pulling) the blade angle lock and turning the angle wheel until it aligns at 45 degrees, as indicated on the angle plate. When you align the angle wheel and release the blade lock, the blade will lock in place.

1). Lay the "R" trim face up on the radial arm saw's resting plate with the outer edge of the trim butted against the saw's rear guide. Usually, trim will taper somewhat, so that the thicker edge comprises the trim's "outer" edge and the thinner edge will comprise the trim's "inner" edge that will fit closest to the door. If you have the inner edge against the rear guide instead of the outer edge, the blade will cut the angle incorrectly.
2). Cut the "R" trim at the cutting mark.
3). Lay the "L" trim face down on the radial arm saw's resting plate with the outer edge of the trim butted against the saw's rear guide. Usually, trim will taper somewhat, so that the thicker edge comprises the trim's "outer" edge and the thinner edge will comprise the trim's "inner" edge that will fit closest to the door. If you have the inner edge against the rear guide instead of the outer edge, the blade will cut the angle incorrectly.
4). Cut the "L" trim at the cutting mark

1). Measure the top trim to the distance equal to the doorjamb's width plus four inches. For instance, if the doorjamb measures 33 inches, you need to measure the top trim to 37 inches because the 33-inch door jamb plus 2 inches of right trim plus 2 inches of left trim equals 37 inches.
2). Mark the cutting line with the carpenter's pencil.
3). Cut the first cut on the "top" trim using the radial arm saw, making sure that the thicker edge rests against the rear guide. If you have the tapered inner edge against the rear guide instead of the outer edge, the blade will cut the angle incorrectly.
4). Flip the "top" trim around, so the narrower side rests against the rear guide.
5). Cut the second angle on the trim, making sure to cut with the butted end fitting right beneath the blade. The end will serve as your second cut mark, so you don't have to make a mark using the pencil.

1). Nail the right trim into place, using the hammer and finishing nails, making sure that the trim's inner edge fits flush against the inside of the door jamb. Place the the nails 9 to 12 inches apart and centered width-wise on the trim.
2). Nail the left trim into place using the hammer and finishing nails, making sure that the trim's inner edge fits flush against the inside of the door jamb. Place the nails 9 to 12 inches apart and centered width-wise on the trim.
3). Nail the top trim into place using the hammer and finishing nails, making sure that the trim's inner edge fits flush against the inside of the door jamb. Place the nails 9to 12 inches apart and centered width-wise on the trim.

1). Sink the finishing nails beneath the surface of the trim by positioning the tip of the countersink against the face of a finishing nail.
2). Sink the finishing nail into the trim using the hammer and countersink. One solid blow should prove sufficient to sink the nail beneath the surface of the trim.
3). Putty the sunken nail heads, using the putty knife and the wood putty. Make sure to scrape away all excess putty.
4). Allow the putty to dry for 24 hours.