How to Cope Joints for Wood Corner Trim
Professional techniques for coping perfect molding and trim joints
IntroductionThe secret for a glove-tight fit for trim corners is a coped joint. With this technique, you can even make complex crown moldings fit without leaving gaps. This age-old carpenter's trick involves cutting the profile on the end of one molding and fitting it against another like pieces of a puzzle. The resulting joint is easy to file and sand for a perfect fit, even on out-of-square corners.
- Coping saw
- Miter saw
What is a Coped Corner?
In a coped baseboard corner, one molding has a square cut on the end that butts up against the wall. The other molding has a coped cut that fits perfectly against the face of the first molding. A coped corner fits tightly, even if the walls are out of square (and they usually are). Coped trim also stays tight-even when the wood shrinks, the walls shift or the vacuum cleaner whacks it.
For baseboard corner pieces, mitering—cutting both pieces of trim at 45 degrees—makes sense in theory. But in the real world, two walls rarely form a perfect 90-degree angle. So getting two miters to meet tight and right is challenging or impossible. And even if you get it tight, the joint will probably open as wood naturally shrinks or swells. Coped corners take these elements out of play.
Video: Coping Baseboard With a Miter Saw
Coped joints for baseboard look great, but can be time-consuming. Instead of using a coping saw, learn to cope baseboard with a miter saw. It’s faster and works great for common baseboard profiles.
Project step-by-step (3)
Make a Miter Cut
- Cut the 'straightaway' with a miter saw.
- Turn the molding upside down, set your saw at least 5 degrees to the right and cut straight down until you hit the curvy part.
- Note: Some pros even nibble away at curved profiles with a miter saw.
- When you make the miter cut, leave the baseboard a couple of inches too long.
- Note: You can cut it to final length after the coping is done. The 45-degree cut will provide a perfect profile to guide your coping cut.
Cut the Cope
- Follow the profile created by the miter cut.
- Guide the blade of the coping saw with your thumbnail to start the cut accurately.
- Pro tip: Relief cuts at tight turns allow waste to fall away and your saw to make turns more easily. You can make straight cuts faster and better with a miter saw (more on that later).
- Pro tip: Coping cuts often create thin, pointy tips on the trim. Support those tips with your finger as you cut, file or sand to prevent them from splintering off.
- Angle the coping saw about 30 degrees to remove more wood from the back of the molding than the front.
- Slowly and carefully saw along the profile.
- Pro tip: Concentrate on staying just outside the line. You can always sand or file away extra material.
Fine-tune the Cope
- Use files, rasps or sandpaper to clean up their cope cuts. Use a small half-round file for tight curves.
- Pro tip: Keep a scrap of the trim handy so you can check the fit as you fine-tune the cope. With really complex profiles, you may have to check and fine-tune the fit a dozen times before you get it right.
Start out straight up
Baseboard often tilts inward at the bottom because of the drywall's tapered edge. And that makes coping tricky. To avoid trouble, make sure the baseboard sits square to the floor. If it tilts, remove it and drive a screw into the framing near the floor. Leave the screw head slightly proud so it holds the baseboard away from the wall. Then check again with your square. You may have to turn the screw in or out a little to get the baseboard to stand straight up.
Brighter is better
With good lighting, you'll get faster, better results. So take a minute to set up a work light or move your workstation near a window.
Clamp it down
Coping thin, floppy trim is like doing dental work on a snake. A clamp or two will hold your work steady and your result will be much more precise.
Coping saw setup
If you're using your grandpa's coping saw-well, actually any coping saw-do three things:
- Replace the coping saw blade if it's rusted or worn. Blades can have anywhere from 10 to 20 teeth per inch; use one with at least 15.
- Make sure the teeth point at the handle; coping saws are designed to cut on the pull stroke (though some carpenters use them backward).
- Make sure the coping saw blade has proper tension. Adjust the tension by rotating the handle clockwise or counterclockwise.