Installing your own baseboards is a satisfying finishing touch to your reno or bunkie build, and it’s probably the easiest trim job for the DIYer. Master the joints you need for baseboards, and the quarter-round is a snap.
1. Mitre joint
Used on outside corners, the mitre joint seems easy to cut, but only in theory. In a perfect world, all outside corners are exactly 90°, but in reality— especially wonky cottage reality—most aren’t. Without building or buying an angle finder, you can get the perfect joint through a combination of rough measuring and trial and error. Place a framing square over the corner to check the angle. If the angle is less than 90°, cut some scrap wood with your saw set at 44°, test the fit, and then adjust from there. If the square won’t fit over the corner, the joint is more than 90°. Do up a test joint with your saw set at 46°—once again, test the fit and adjust. Once you have your angle dialed in, go ahead and cut the baseboards.
2. Coped joint
In contrast to the mitre, this joint—for inside corners—seems complex but is actually pretty easy. Determine which piece of trim will be coped by standing in the doorway of the room. In most situations, the piece with the end facing away from you is the one you want to cope, after butting the other piece into the corner. To fashion the cope, the first step is to cut the end of the baseboard at 45° with a mitre saw—as if you’re making a mitre joint. This will reveal a shaped line where your cut meets the baseboard face. Using a coping saw, cut exactly along that line, removing the mitred portion. What will remain is a piece that fits exactly against the face of the other baseboard (which is just butted against the wall).
Tip: Angle the coping saw a few degrees backwards as you cut the joint. This slight angle (known as a “back cut”) helps ensure a tight joint.
3. Scarf joint
If you need to join two baseboard pieces along a long wall, and you butt the ends, the seam will show. A scarf joint, on the other hand, is practically invisible. The joint is simply two 45° cuts laid over one another with the visible tip pointing away from the door or towards the biggest, brightest window.
Tip: If you’re painting baseboards, paint them before installing. To hide nail holes, apply masking tape where you’ll be nailing and drive the nails through the tape. With the tape in place, fill holes with paintable acrylic caulking. Touch up the paint; remove the tape when the paint is dry.