Crown Moulding and Cathedral Ceilings

The joint between horizontal to rake treatments when applying crown in a cathedral-ceilinged room involves some complex geometry, and usually creates awkward visuals. Here's more discussion on this pesky problem. April 6, 2007

I'm looking for advice on installing crown moulding in a room with cathedral ceilings. It's the second floor of a cape with a new dormer. One side is a 10-12 pitch and the other is a 3-12 pitch.

There are 2 problems as I see it: First, the piece running down the slope will be wider than the piece running horizontally. So the pieces won't match when they meet. Second, on the horizontal piece, the top won't be butting against a level ceiling, so how do you get a tight fit on the ceiling? Do you just need to shave the back to the right angle?

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
In the upper right corner is a search box. Type in "crown on cathedral ceiling." There are six threads there on this subject.

From the original questioner:
Thanks. I've read all of this before. While some of it applies, I was just hoping that someone (a professional trim installer, maybe) had come across a different way to tackle this issue.

From contributor J:
I usually cheat by making some kind of a transition piece.

From contributor W:
To mate properly, the raking profile and the horizontal profile must be different. This is how it was traditionally done. You can derive the raking profile from the regular one with simple drafting techniques, then it's a custom run of that profile.

From contributor B:
Contributor W is exactly right. If you are going to miter the rake into a 90 degree turned horizontal run, one of the two runs needs to be a smaller profile than the other. That is, same profile but scaled down. If I am visualizing it correctly, the rake moulding would need to be the smaller version of the profile.

You can miter the bottom of the raked run to horizontal in the same vertical plane with a small triangular piece of crown at the bottom, and then miter (or cope) that into the 90 degree turn. That works but some will think it's not a clean looking solution.

As far as I know, those are the only two solutions to the problem. This problem is why return jets were designed into Greek Revival architecture in New England. The rake edge crown came down and sat upon a shelf. This shelf was created by the run of crown across the front of the building making a horizontal 90 degree turn around the corner, and going about 24" back along the side wall of the building. A shelf was set on top of the short piece that was now on the side of the building, and the rake crown came down to that shelf. Very tricky stuff. The issue comes up on a fairly regular basis.

From contributor Y:
You can add a small piece that mates to both, but I think it a clumsy solution.

From the original questioner:
This is exactly why I wanted to start another thread on this subject. You guys really know what you are talking about. Contributor W, I think you are exactly right when you say that a small piece to mate both the rake and the horizontal piece would look clumsy. I think I'll spend a little extra and find multiple scale pieces to do the job right. Do you have any online sources for this kind of moulding, or do you make them in your shop?

From contributor W:
I make moldings on a shaper. Knives can be custom ground to match my drawing or sample.

From contributor I:
The piece is not just scaled up or down in width, but the profile is altered and it is dependent on the rake angle. As contributor W said, the profile can be generated with drafting techniques. Then knives cut to fit each different rake angle. I have seen 4 different rake angles on the same house, calling for 4 different rake profiles. These were for outside, but the idea is the same.

From the original questioner:
So maybe I should ask this question. What would you do if it were your house(s)? I have just 2 rooms to do for a total of about 500 sqft. I am not new to woodworking (I make tables, cabinetry, etc.), so cutting compound miters is not really a problem. I'm just looking for a nice clean look that will not cost me a fortune.

Would you spend the money on custom moulding profiles (what would this cost, anyway?), would you go for the Gary Katz method, or would you use corner blocks?

From contributor U:
Both contributor B and W are right on the money.

Here is an example of just how much the profile changes. You can print them both in full scale if you want to see how much the profile changes. Crown 4.500" is for the straight runs. Crown 5.000"-6 is the same crown for a 3/12 roof pitch. It was quite a project in layout. The bevels on the backcut angles changed as well, from 45* to 39.5* and 50.5*. The rake determines the degree of the bevels.

Click here for higher quality, full size images

From contributor I:
Thanks for the drawings, worth 1000 words.

To the original questioner: to answer your question, I would make the knives for an outside corner. For an inside corner and only two rooms, price is the big obstacle. I am sure contributor U could quote the knives. Then it is a price/look decision. Knives cut for the rake angle is the least noticeable, most expensive option. Gary's method comes in second as far as least noticeable. The corner block or dropped post look is eye catching and that could be good if there are other elements in the room to compliment it. For example, posts, columns, large fire place mantel, etc. The size of the crown and corner block would also influence my decision.