I'm hanging crown moulding (typical profile) along a convoluted contiguous line in a high foyer. The runs and miters vary, and the height and interferences make the project a challenge. But one spot in particular has the project at full stop. Take a look at the image below: The blue line indicates the line that has stumped me.


The slope of the ceiling is 30°. The crown follows this slope, then must turn 90° (forming an outside corner) for a horizontal run, then turn another 90° (forming an inside corner) to resume the 30° slope. My problem is, I cannot figure out how to transition the crown at these two corners.

I've modeled the area in CADD to help me evaluate options with actual geometry:


The image below illustrates the problem. The trim shown in the image are identical. You can really see how the ceiling slope creates a transition problem at the corners.


I looked at pendants in CADD; They look ridiculous, so I'm not going that route.

I found that a smaller-dimension identical-profile crown sorta works at the corners. The transitions aren't perfect, but close enough given the height. I'm more concerned that the smaller trim used for the horizontal run will look disproportionate.



That's my dilemma. Any experienced trim carpenters have some suggestions for me to consider?

 

The easiest way for you to do this is to make 2 mockups. One inside corner, one outside corner. Both normal 45 degree miters, glued and nailed together. Make them about 16" long or so. Then place each of them on the wall at the correct spring angle. (This is critical, since it throws all your miters off if you don't) Trace around the top and bottom edges, marking where the inside and outside miters fall on both the ceiling and the wall. Then take them down and use those lines to determine the lengths of all your pieces. Double check that the distance from the ceiling to the bottom line is the same on both side walls. If it isn't, your spring angle was off on one or the other. Also double check the level line on the wall with a level (on wall parallel to the handrail).

All 3 pieces will be cut from the same size crown and will mitered together normally. The bottom edge--- on piece of crown that sits on the wall that is parallel to the handrail--- will not sit square to the wall like it does on the side walls. It will be pitched down at a 30 degree angle to that wall. That's just the way it is if you want to avoid a plinth block at the miter.

For other transitions going down the other side, you can make a triangle transition. I think youtube has some videos, if not I can try to find a website that explains the triangle transitions.

 

Thanks!

I've read... and re-read... you explanation a bunch of times. I've rendered in CADD what I believe you describe:

Step 1:


Step 2:


Step 3:


My gawd. I can't believe how obvious the solution was. Christ on a cracker--you wouldn't believe the time I've spent studying this problem. Thanks for pulling me back into the shallow end.

For the bottom of that 30° run, the "triangle transition" looks like this:


Thanks for your explanation. Looks like I'm back in business.
...to the saw! Hooooo!

 

Correct. If you need a video, go to YouTube and search for: "installing crown molding on a vaulted ceiling without transition piece".

 

Annnnd... it's up!


I made a Z-shaped, three piece unit, hefted the thing to the apex, pivoted it 30° and shot it home.

Thanks, XSleeper, for taking the time to post. I genuinely appreciate it.

 

That is great, I've done lots of crown molding but never on a cathedral ceiling!

 

Nice job. Gluing and pinning your pieces together as a unit is nice to do wherever possible.