Installing a 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 (Fig. 1). 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.
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, 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 (Fig. 2), cut it with handsaw (a back saw is actually a better
choice) (Fig. 3) 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 (Fig. 4). 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 or hand saw. This cut must be straight. At this time it is also a good idea to
lightly sand the piece.
Install the Threshold
Once you have the threshold cut to length, slide it onto the area that needs covering (Fig. 5). 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 (Fig. 6). 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 bitit 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. Drywall screws work very well for
this. Now cut the dowel to approximate lengths, place wood glue around the outside and slide them into the holes (Fig. 7). 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. 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 finish you like.
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