How to Make an Interior Threshold

Preparation

• Open the door, and have an assistant hold it in its upright position while you retract the hinge fasteners from the jamb. Lift the door away from the work area. If updating a preexisting jamb, use a reciprocating saw to make a cut through the center of the original, retract any fastenings, and then lever the two halves away. Retain them for use as a template. When eventually reinstalling the door, do not simply hold it in the open position and reinstall the hinge screws; first position it in the doorway as though closed to ensure that the new jamb still allows it to close properly. Some trimming at the bottom may be necessary.

New Thresholds

• If installing the doorway from scratch -- for instance, if a new room has been added and a new doorway cut into the dividing wall -- it is an easier project to fit the threshold first, because less shaping and trimming is involved. Simply measure the width of the door, transfer the measurement, and use a circular saw to cut the threshold to size and fit it in place, then move on to fastening.

Replacement Thresholds

• If the jambs are already installed, mark their convoluted profiles at each end of the threshold to allow it to fit tightly around the jamb and the door stops, then use a jigsaw to cut out the shapes. If updating a preexisting threshold, use it as a template to mark the replacement. Once the new threshold is cut, put one end in place, and use a rubber mallet to tap the opposite end down.

Fastening

• Attachment can either disguise the fasteners or make a feature of them. To disguise the screw heads, drill the pilot holes, then use a larger bit, sized to the head of the screw, to make a rebate, or rabbet, into which the entire head can be drawn. Drive the screws down until they are entirely below the level of the surface of the wood, then glue plugs above them. A plug is not a dowel: Dowels are cut along the wood’s grain and cannot match the threshold; plugs are cut across the grain, so the marks in the wood run laterally as they do through the threshold. It is possible to make plugs from off-cuts of the threshold itself. After finishing, this method makes the work almost impossible to see. Proprietary plug cutters are available from specialist tool stores.

  To make a feature of using decorative fastenings such as brassed non-domed screws, use a countersink bit and leave the heads flush but revealed. For neatness, align all the slots parallel across the doorway from jamb to jamb. Raised screw-heads set in cup washers are impractical; the “brassing” -- the applied colored surface -- will quickly be abraded from the base metal of the screw by foot traffic.