How should my base molding interface with a stair skirt?

Question

The trim sort of...drops off, and it just doesn't feel right, but my brain can't figure out what to put in this empty space.

Answer 1

You want to find trim/moulding that matches the design of the top piece (it looks to be about an inch wide) above the 1x6 flat piece.

Cut the new piece to match the cut at the top.

On the bottom, the easy way is to just cut the new piece to lay on the top.

The harder way is to remove the trim at the bottom and cut the corner/mitre the other way (⟍) instead of the way it is cut now (⟋), splitting the total angle in half.

The new piece will be cut to match the new cut on the bottom piece, so the trim design will flow into the bottom piece, instead of laying on top.

The cuts need to be exact to look good. Practice on extra trim first will help. Usually trim will come in 8 foot pieces, and you only need about a foot.

Answer 2

crip659 describes the proper way to miter this all together. If you're feeling overwhelmed by the prospect, consider a plinth block. These are readily available at home stores, or you can simply cut a bit of wood that's slightly thicker than the other moldings (you don't want flush joints). Sand it and paint it before installation.

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In your case, ideally it would be wide enough to eliminate the awkward angled baseboard segment. You could plumb it, trace it, and use an oscillating saw to cut a channel, then just caulk it in place.