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Project Guide

How to Install Door Trim

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Prepare to Install Door Trim
person marking out the reveal on a door

For a consistent look, match the interior trim around your door to the style of the room. Before you cut, start installing by marking out the reveal, the gap between the trim and the edge of the door jamb or door frame, which is typically 1/8 inch.

Calculate the Side Length
person using a set square to measure a door jamb

For the next step, adjust the blade on your set square to 1/8 inch and put the body against the door jamb. Place a sharp pencil against the end of the set square blade, and run along the length of the jamb, drawing a line for the reveal. Repeat this process for all three sides of the door jamb.

Calculate the Head Length
person measuring a door to place head moulding

Calculate the length of the head moulding by measuring the distance between the vertical reveal lines you've drawn on either side of the door jamb. Hold the head moulding piece above the door and draw a line indicating the direction of the miter cuts on both ends of the trim. 

Make the Cuts
person cutting wood for trim using a miter saw

Now, it’s time to cut. Set the power miter to a 45-degree angle. Cut the first miter on the head moulding piece. Then, measure the length of the moulding from the inside point of the miter you just cut to the desired length. Make a mark before you cut another 45-degree miter with the power miter. Nail the head moulding piece to the door jamb with trim nails. Use 3d or 4d nails every 12 inches along the bottom, and 6d or 8d nails along the top of the moulding piece.

Tip: To prevent splitting during this step, avoid nailing 1/4 inch from the side edges and an inch from the edge of the moulding. 

Cut the Leg Moulding
person nailing leg moulding around a door

Position the leg moulding piece against the door jamb. Again, draw a line to guide the miter cut. Measure the length of the leg moulding from the inside corner of the head moulding piece to the floor and cut the leg moulding at a 45-degree angle. Nail the leg mouldings in the same manner as you did across the top of the door frame.

Finish Cleanly
person filling divots with spackling compound

For the last step, use a nail set to drive the nail heads below the surface of the door trim. Fill the divots with spackling compound for a clean finish.