Installing a Door Threshold to Bridge a Large Gap

Thresholds are common fixes for areas where the floor is at different levels.  This commonly occurs when putting a new floor covering over an existing floor.  Tile floors are a common culprit due to the use of cement board and other substrates.  The first task is to identify what kind of threshold you need.  In the pictured installation there was a little bit of plywood protruding from under the tile.  We chose an oak threshold that fit over the plywood edge but was still wide enough to fill the doorway.  Your project may not have all of these factors but we chose a complicated installation to illustrate the possibilities.

For this project you will need a drill, spade and twist bits, sandpaper (power sander is handy), hand saw, screws, wood glue and dowels to fill the holes (countersinks) you drill.

Door threshold

Door threshold

Level of Difficulty

Time Required:
 2 hours
 
 
Tools:
Chisel
Electric drill
Spade bit
Hammer
Screw driver
Back or handsaw
Tape measure or folding rule
Materials:
Wooden door threshold
Wood stain and finish
Wood dowels
Wood screws
Safety Precautions
Use safety precautions with power tools - eye and ear protection.

Preparations

The first thing to do is to clean up any gunk that is in the area.  The next thing to do is to trim any molding that may be in the way.  In the picture at left, the stop molding for an old door needs to be trimmed so that it doesn't interfere with the new threshold.  Alternatively, you could take it off.  After you mark the trim, cut it with a handsaw (a backsaw is actually a better choice) and then use a chisel to remove the material.  Make sure that you get it all or it will interfere with a clean installation.

Next you need to cut the threshold to the proper length.  Measure the opening you need to cover and transfer that measurement to the threshold.  It is a reasonable procedure to cut the threshold a bit long (you can always trim more off) to make sure that you don't have to go back to the store.  Use a square to extend the line across the threshold. 

Carefully cut the threshold to the proper length.  Do not try to "freehand" this cut.  If no power saw is available, such as a cut-off or table saw, use a miter box with a back hand saw. This cut must be straight.  At this time it is also a good idea to lightly sand the piece.

Mark molding at top of threshold for cut

Mark molding at top of threshold for cut

Saw molding

Saw molding

Measure inside distance (use a folding rule if you have one)

Measure inside distance (use a folding rule if you have one)

Install the Threshold

Once you have the threshold cut to length, slide it onto the area that needs covering. You should now decide how many screws are necessary to hold the threshold in place. If a hardwood threshold is being used, you will need to countersink the screws in order to conceal the screw heads. The best way to do this is to first drill a hole with a spade bit that is a bit bigger than the head of the screw. Use a regular size bit (1/2" or 3/4") as a dowel will be used to fill the hole later. Do not use a normal twist bit, it does not cut the wood fibers around the edge of the hole and, as such, a ragged appearance results. Next, use a normal twist bit that is a smaller than the shank of the screw to drill a hole through the bottom of the previous hole. Do this for all locations where you want screws.

If you are happy with the location of the threshold, go ahead and secure it to the floor. Use appropriate woodscrews and try to avoid drywall screws as they do not offer the strength needed. Now cut the dowel to approximate lengths, place wood glue around the outside and slide them into the holes. Wipe off any glue that squeezes out. Let the glue dry before proceeding any further.

Next the dowels have to be either cut off or sanded down flush with the surrounding wood. There is a Japanese saw that is great for this. It is called a "Kugihiki" saw and you can find it here. It cuts nearly flush but does not mar the surrounding surface. Alternatively, you can always just sand the dowels flush. Either way, give the threshold a final sanding and wipe it clean. Finish it with whatever stain finish you like. I normally use an alkyd-based polyurethane.

Slide in threshold beneath molding

Slide in threshold beneath molding

 Spade drill for wooden dowel plug

Spade drill for wooden dowel plug

 Dowel plug to cover screw head

Dowel plug is glued in place to cover screw head