How to Build a Door Jamb

Making it Work

Doors take more abuse than any other part of the house. This means the trim that the door closes against needs attention quite often. However, if you are to the point that paint is not going to do it this time, then it is time to build a new door jamb. This article covers how to build the jamb apart from the door to prevent purchasing a whole new unit.

Things You'll Need

• 1 x 6 lumber
• Table saw
• Carpenter's square
• Electric miter saw
• Straight edge
• Router
• Straight bit
• Door shims
• Hammer
• Carpenter's level
• Wood glue
• 6d finish nails
• Door stop
• ¾-inch brads
• Nail set

Instructions

Setting it Up

1. Set the table saw fence on 4 9/16 inches. Rip the lumber to this width.

2. Measure the width at the top of the door opening. Measure from one end of the lumber and make a mark at that measurement. Place the carpenter's square on the mark and draw a line across the width of the lumber. Cut this with the electric miter saw.

3. Measure the height of the opening for the door and subtract ¾-inch. Measure from one end of the lumber and make a mark representing the height of the door opening. Place the carpenter's square on the mark and draw a line across the width of the lumber. Cut this with the electric miter saw. Repeat this for the other side of the door opening.

4. Measure from one of the long edges and make several marks at 1 3/8 inches. Place the straight edge on the marks and draw a line parallel to the long edge. Write an "X" on the right side of the line to indicate where the door stop material will be installed.

5. Measure the distance from the top of the door and the top of the hinge. Mark one of the long pieces accordingly. Measure the length of the hinge also and mark the lumber at this mark as well. Place the carpenter's square on these marks and draw a line across the width of the lumber.

6. Next, measure the distance between the hinges on the door and mark the lumber. Then measure and mark this hinge the same way as the hinge in Step 5. Place the part of the hinge from the old jamb on the marks and draw the outline of each.

7. Set the router to the depth needed to take out the thickness of the hinge. Cut out the area where the hinge will be installed. It is imperative for it to be flush with the surface of the jamb.

Installing

1. Place the top piece of the door jamb at the top of the opening. Place the carpenter's level on it to be certain it is level. Insert shims if necessary, and secure the top piece with the finish nails.

2. Set the lumber with the hinge cutouts against the appropriate side of the opening. Place the carpenter's level on it to be certain it is plumb. Use shims where necessary, and secure the jamb with finish nails. If this side is not plumb, the door will move accordingly.

3. Measure the width of the door. Place the measuring tape against the top of the jamb with the hinge cutouts, and make a mark representing the width of the door plus 1/8-inch. Drill a pilot hole near the top of the other piece of the jamb. Set this piece on the mark at the top of the jamb. If it is not against the 2 x 4 in the wall, insert shims to make a snug fit at the top of the jamb. Insert a finish nail in the pilot hole and tap it with the hammer until it holds the top of the piece in place.

4. Place the carpenter's level against this piece to be certain it is plumb. It also needs to be the same distance from the other side at the bottom as it is at the top. It is more important for the gap between the door and the jamb to be the same than it is for it to be plumb. In most cases, there won't be enough difference to make a difference.
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5. Secure the jamb to the opening. Measure and cut the door stop material, beginning with the top piece. Apply wood glue to the side of the line with the "X"s, and secure the door stop with the brads. Trim both walls around the jamb with door casing. Paint or stain it before hanging the door. For more on door casing, see "How to Install Case Moulding around a Door" in the Reference section below.

Tips & Warnings

• Drilling pilot holes in the lumber will make for easier installation. Set the nails with the nail set. Apply wood putty and painter's caulk before sanding.

• Do not set the table saw blade any higher than necessary to make the cut. Do not make the cutouts with the router before testing the depth on another piece of lumber.

References

• Custom Door Jambs
• How to Install Case Moulding around a Door

Resources

• Custom Door Hanging