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For the baseboard in the picture below, would you recommend coping, mitering, or butting the internal corners? The profile is about 7" high and .5" think. I intend a paint finish.

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isherwood
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Wynne
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2 Answers2

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Unless you are very good with a coping saw, that should be mitered. However remember not every corner is exactly 90 deg. Get a proper measurement and adjust your miter saw accordingly.

RMDman
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    Good point about a corner might not being 90 deg. Difference between a perfect mitre and maybe just okay mitre. – crip659 Nov 10 '22 at 22:34
  • One rule of thumb is cut inside miters 44 degrees each side, cut outside miters 46 degrees. – Jack Nov 11 '22 at 05:23
  • So if my inside corner is a true 90°, I should still cut 44° and push the 2° gap closed by taking advantage of the compressibility in the wood? – Wynne Nov 11 '22 at 19:01
  • Not so much the compressibility of the wood, but as the mitered corner will never be perfect, @Jack's suggestion is to "cheat" the angle slightly so the most visible edge will be tight at the expense of the hidden side of the corner having a slightly bigger gap, which is visible only on the short edge of the miter. – spuck Nov 11 '22 at 23:30
  • Since the material is painted and assumed the top will be caulked to the wall, by default the ever so slight gap at the inside corner will be caulked while doing the rest. – Jack Nov 12 '22 at 00:59
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This is a matter of opinion and prior experience. I've done plenty of this profile, and mine is that coping will yield the best outcome. Inside miters are difficult to make tight while keeping them aligned, and they don't tend to stay tight.

The right round file, sanding rod, or Dremel barrel would make it fairly simple. The fact that you're painting means you can fill any imperfections.

  1. Cut the piece to length1 at 45°, as if you were going to miter it.
  2. Flip the piece and cut at 90°2 down the flat face at the corner created by the initial cut.
  3. Optionally do a rough cope of the bead with a fine-bladed coping saw.
  4. Finish the bead to the initial cut with a suitable round file (or sandpaper around a dowel or drill bit).

1) The beauty of a cope is that you can force it in a bit for a lasting, tight fit. Add ~1/16" to your length, then flex the piece out at the center while you set the ends. You can't do this with a miter as easily--the two pieces tend to shift against each other.

2) Back-cut slightly (1-2°) to be sure the front edge remains tight. Drywall corners often curve into the room a bit at inside corners, meaning the ultimate angle is somewhat more than 90°.

isherwood
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    I find it beneficial to sand the back inside corner of the molding to take off the edge so that it fits nice to the inevitable rounded corner of the drywall. If you cope the joint you only need to do this on the first piece that butts into the corner. If using miters you end up having to do this on both pieces. – Michael Karas Nov 11 '22 at 23:28