How best to cut (slightly) varying size notches in long piece of trim

Question

I created a ceiling in a room in my basement by affixing short pieces of wood between each ceiling joist. The bottom of each joist is slightly proud of the ceiling boards (~3/16" but slightly variable). It was a bit laborious, but it looks pretty good (at least I think so), and it maximizes headroom.

Now I am going to install trim along the intersection between the ceiling and the wall to cover up gaps. I suppose this might technically be called crown moulding, but in the basement that doesn't feel like quite the right term! Anyway, I'm planning to use simple 3/4" boards to do so (probably 2 1/2" or 3" wide).

Here's a closer image of the intersection between wall and ceiling.

My question: is there a clever way to install the trim? It seems outrageous (impossible?!) to make mitered corners around each joist, as each protrudes down only a 1/4" or less. So it seems like cutting notches into a long piece of trim is a better way to go - although the notches would not all be exactly the same depth. And cutting them precisely seems like a challenge - any tips on good ways to do so? Or...are there better ways to approach the trim?

If it makes any difference, ideally the trim will be left as its natural wood color, not painted.

If this post belongs elsewhere on stack exchange (e.g. "home improvement"), please feel free to move it.

Answer 1

So it seems like cutting notches into a long piece of trim is a better way to go - although the notches would not all be exactly the same depth. And cutting them precisely seems like a challenge - any tips on good ways to do so?

You've probably already thought of, and are dreading, this but cutting notches one at a time to the requisite depths is pretty much the only way I can think of to do this cleanly. And really, the measurement of each required depth and the transfer of same to the trim pieces is most of the added effort — it doesn't affect the actually cutting of the dados much or at all (depending on the techniques used).

You only need to do the job once, and once you're done you're done if you know what I mean. However, it is a lot of work regardless, which is already a hurdle, and adding effort on top of that is sure to be onerous.

Alternatively
Cut all notches to the same depth (the maximum needed) and then insert shims to hide any egregious gapping for the joists that project less. The shims will serve no structural purpose so they can be quite rudimentary and still serve their purpose, and taking each to its required thickness is easy by hand plane or fairly easy by belt sanding..... mind your fingertips!

This isn't a perfect solution by any means, but it strikes me as a massive saving in effort and quite a saving in time.

Or...are there better ways to approach the trim?

Possibly, but not without their own effort and difficulty needs.

The only other options I can think of are notching the joists, which is problematical in a couple of ways, and making them flush towards the ends.

The second is doable but not without its challenges, and I'm not sure if the slow slope towards flush at the walls won't look odd. Perhaps the slope would go largely unnoticeable by itself (I'd bet on this personally) except for the change in colour, that is sure to draw the eye — the freshly worked wood will be starkly different to the current aged colouring, and that alone might rule this out as an option.

Answer 2

Frame challenge: don't add the trim.

Instead, use a suitable filler for the walls applied in the gaps (e.g. left joist in your 2nd photo), painted to match the walls. Any stray paint on the joists can be scraped/sanded off if it's too obvious (right joist in the same pic). People don't often look up much, so the change in surface finish on the joists shouldn't matter; it may even be enough to allow you to ignore the odd paint spot, depending on your lighting and the use of the room.

In plenty of places a bead of silicone sealant (or another very flexible caulk) would be run all round the edge, though this wouldn't be my preferred option.

Answer 3

I think your plan works. I don't think it will be as much work as you think if you plan ahead a bit and use a couple of tricks.

First, get your trim board(s) to the correct length. Then position the trim under on the wall, maybe an inch from the ceiling. The key in this step is keeping a consistent distance between the top of the trim and ceiling. Secure the trim in place temporarily. You might be able to do this with double-sided tape, but make sure it stays in place. Use some trim nails (don't send them home) for this if necessary.

Once you have the trim in place, take a compass (like for drawing circles) and set the gap to just slightly more the distance between the where the trim is and the ceiling. Hold the compass such that the pencil is on the trim and the other point is in corner between the wall and the ceiling. 'Scribe' a line by pulling the compass along the wall and around the boards. This will mark the position, width, and depth of each board.

To cut the notches, take the board down and using a sharp handsaw (I like Japanese-style pull saws for this kind of thing) cut the depth of each notch on each side of the traced board markings. Then, with a sharp chisel (or set of chisels) cut the notches out. Do this by holding the chisel perpendicular to the piece. The flat side of the chisel should be towards the part you want to keep. Cut with the chisel between the two depth cuts from before by firmly whacking the handle chisel with a mallet or dead-blow hammer. Don't do this on a surface that you care about and which might be damaged, but don't do it on a hard surface (like concrete) because your chisel will dull rapidly.

Once you cut out all the notches, slide it up on the wall and see how you did. You might want to take a scrap piece and do a little practice first. Good luck!

Answer 4

I agree with the answer from @graphus, but just to throw out one last idea…

Make your ‘crown’ a two-piece affair, with a skinny and slightly deeper part running between the joists (and flush with the bottom of the joists), then run the wide stock around the entire room.

The cutting is still laborious with the extra fillers (probably a track saw or similar guide, depending on how tapered each piece is), but it’s certainly more forgiving than getting accurate notches in long sticks. This also assumes that the difference between the joist bottoms is subtle enough that you’ll be able to bend the wide stock to conform. Aesthetically? Well, you decide.

Answer 5

Cutting notches in the trim is likely the most straightforward approach, but it's definitely labor-intensive and requires precision. A router equipped with a plunge base can be used to cut the notches. This can help you maintain precision and depth control.

Answer 6

Masking tape, polyurethane filler (paintable), remove tape as you go to leave a crisp edge around all the boards, but feather onto the wall and paint would me my humble opinion.