I finished the project six hours later. Tired and frustrated, surrounded by a small pile of discarded trim pieces and two empty pint containers of putty, I sat on the floor wondering how professionals could install base trim so quickly and precisely.
It wasn't until I began working as a carpenter years later that I learned the secret of coping — cutting along one piece of trim so that it fits perfectly against the shape of another piece. Coping is a very easy skill to learn. Although coping crown molding can be more difficult than coping inside corners of base molding (as shown here), the basic principles are the same. Try using these seven steps for a faster, more precise trim installation.
Step 1: Install the first piece. Fasten the first length of base trim to the wall parallel to the entryway of the room. This way, the coped joints will not be easily visible to someone entering the room. Both ends of this first piece are cut square to fit snugly between the adjoining walls.
Step 2: Determine the length of the second piece. Measure the length of the wall that adjoins the trim you just installed. Make sure you measure from the flat vertical portion of the installed trim. Butt your tape into the existing trim as shown in the picture (see photo below).
First install the molding that the coped molding will abut. Then measure from the flat, vertical portion of this base trim to the opposite wall to determine the length of the coped molding.
Step 3: Make the "back cut." Set your miter saw bevel to 45 degrees. Then mark the second trim piece using the measurement from step two. Make the cut as shown in the photo below. When you are cutting, keep your mark to the inside short point of the 45-degree blade and not the outside long point; otherwise your piece will end up being too short. This "back cut" is the cut you will cope to fit against the first piece of trim.
Use a miter saw to "back cut" a 45-degree angle at your measurement mark. The piece to be installed is on the left, and the measurement mark is to the left of the blade.
Step 4: Begin coping the back cut. Start at the base of the trim piece and cut along the inside of the 45- degree bevel. I like to use my miter saw to cut along the vertical portion of the bevel before finishing the cope with a hand coping saw. You can do this by laying the trim flat or, if possible, orienting the piece vertically on the miter saw table. Either way, allow the saw to cut only the straight, vertical portion of the trim as shown in the photo below.
Use the miter saw to cut only along the straight, vertical portion of the trim piece. Stop your cut before the curve in the trim piece.
Step 5: Finish the cope. Using a coping saw (available at a hardware store for about $10), slowly continue to cut along the inside angle as shown in the photo below. Keep your coping saw at a 90-degree angle to the piece to allow for a straight, clean line.
Finish coping by slowly cutting along the angled cut line. Keep the coping saw blade at a 90-degree angle to the trim piece. Then use a file to smooth the edges.
Step 6: File the edge. Smooth any uneven ridges or dips in the coped cut with a small rounded file.
Step 7: Install the coped piece of trim. Notice in the photo below how the coped piece fits nicely against the first piece of trim installed. That's it! Two pieces of base trim installed and you've just finished your first cup of coffee! Continue the same steps with the remaining corners of the room and you will easily finish by lunchtime.
Check the fit of the molding, make any necessary adjustments; then install the trim with finishing nails.
Coped crown molding has some advantages over the mitered variety, and it's the preferred joint for most architectural restoration. With enough practice you can become proficient at coping crown molding with a handsaw, but if you'd rather use a power tool for the job, accessories can enable you to make coping cuts with a jigsaw.
The EasyCoper ($37) includes two simple plastic jigs (for a right or left cut) that accept crown molding up to 5-1/2 in. wide. (The company also sells a jig for base molding.) The jig's easy setup and affordable price makes it ideal for DIYers.
The Rockler Speed-Cope ($150) is a sturdy, versatile unit that can handle both crown and base molding up to 7-1/4 in. If you're a professional or you're working on an extensive remodeling project, this is probably your best choice.
Note that these units do not eliminate the need for a miter saw. You'll still need to cut miters before making coping cuts.