When installing a new floor, door jambs can be particularly frustrating to work around. If you don't already own a "Jamb Saw", you should definitely get a manual (Figure 1), electric (Figure 2), or maybe even a cordless tool, from your local hardware store before getting started. This will ensure a perfect job for cutting these pieces. The following steps will describe the process for an installation where floorings of different thicknesses are applied into adjoining rooms.
Step 1 - Measure the Door Jamb Area
Measure and mark a line across the width of the doorway where the tile from one room and the laminate from the next room will come together.
Step 2 - Prepare the Laminate
Next, place a piece of scrap laminate on a piece of underlayment and press it up against the front of the doorway. Mark the height of the laminate and underlayment thickness along the jamb and the door molding. Do the same thing on the opposite jamb. This will serve as your cutting line for the laminate side of the door jamb.
Step 3 - Prepare the Tile
Place a piece of tile on the backside of the doorway up against the jamb of the adjoining room. Add ¼-inch (or whatever the thickness of your inset), and then make a mark against the door jamb and molding.
Step 4 - Preparing to Cut the Laminate Side
As a safety precaution, you must unplug the power tool before performing any adjustments. Adjust the depth of cut on your undercut saw to the height of the laminate side of the door jamb. Check and double-check this measurement.
Step 5 - Cutting the Laminate Side of the Door Jamb
For this step, wear safety glasses. You can now plug the tool into the outlet. Start by cutting the front portion of each side of your doorway as shown in Figure 3. Ensure that the laminate side is lower than the tile side. This will help in case you overlap your cut a bit—it won't ruin your door jamb.
Step 6 – Cutting the Tile Side of the Door Jamb
Reset the undercut saw to the height measurement of the tile side. Cut the side of each side from the center through to the door trim.
Once you've completed this step, you can finish your flooring.