Crown molding on a pitched ceiling

[Mace68]

The crown molding calculator on this site is great, but I also have a pitched ceiling angle to account for. How do I figure in the pitch angle?

Thanks.

[Rich]

I've been meaning to make that calculator too. Try this out in the meantime...
http://www.josephfusco.org/Articles/Crown_Moulding/rakecrown.html

[Mace68]

Thank you very much for the link :)

[Mace68]

My math skills are rusty to dead :?

Anyway, since all of my crown molding is the same width with an angle of 38/52 and I have a rather small pitch angle (let's say 15°), would this work reasonably well also?

Eave miter = 38° (same as the rake crown wall angle)
Rake miter = Absolute value of pitch angle (15°) minus eave wall angle (38°) = 23°
Eave and rake molding bevel = 45°

As you can probably tell I'm brand new to all of this so all help is greatly appreciated.

Thanks.

[Rich]

Oh..
Josephs' article assumes a wider crown on the rake. Which assumes you can scale your crown to get all the ridges etc to plane in.. :( That's not easy unless you have a molder and a way to cut your own knives. With the same width crown the rake molding will never reach the outside corner of the level crown.
Here's an option - not sure it will work for the look you want. You could put a block on the corners and butt the crown into it.

[Mace68]

The block sounds like a very good idea. I will do it that way if my pitch angle is large enough to make the mis-match in width at the corners too obvious.

Thanks again for all your help.

[Tom R]

Drop the eave crown angle and raise the rake crown angle each one half of the difference of their vertical 'footprints', then they'll meet.

[Mace68]

Sorry for my ignorance, but could you give me an example of what you mean using my angles of 38/52° crown molding, 15° pitch angle, 45° bevel if possible? :?

Thanks.

[Tom R]

Oh, man, you're tough. I'm not too bad at math (until now), but this one's for 'Einstein'. I can't give you exact numbers, it's more of a trial and error method with that 15 degree pitch you're throwin' at me, but let's give it a try. First of all, I don't know what size crown you're using, but that shouldn't really matter, beings we're mainly going to work in 'degrees'. For the sake of argument, let's say you're using a 2 5/8" crown (38/52), and the point where the bottom of your 'eave' crown meets your 'eave' wall is, say, 2 1/16". Now let's say your bottom point of your 'rake' crown hits your 'eave' wall at 2 3/16". Your difference is 1/8". To make up that 1/8", you're going to 'cheat' your 'eave' crown down 1/16" (guessing maybe 36 degrees), and your 'rake' crown up 1/16" (guessing maybe 40 degrees). Note, there will be no mis-match in width (because the 'bottoms' are both at the 2 1/8" point, and the tops will be aligned because of your 'degree' adjustments), but there will be a slight mis-match in 'profile' (which you'll get away with because we're only talkin' a 15 degree pitch differential).

To get a really nice job you would also slightly 'backcut' the bottom back edge of your 'eave' crown, and the top upper edge of your 'rake' crown, so you wouldn't see slight gaps where the eave crown meets the wall and the rake crown meets the ceiling.

Now keeping in mind I'm in my office, not out in my shop, and that 'cheating' 2 degrees in each direction is just a guess, here's what your cuts would be.

Eave Crown (36/54) M=30.4 B=34.9

Rake Crown (40/50) M=32.7 B=32.8

Hope this helps get you started. 8)

[Mace68]

Thanks very much for the info. This helps a lot.

[Tom R]

Sure thing, let us know how you make out.

P.S. I did some 'barnyard' math (my specialty), and I actually come up with 2 1/4 degrees in each direction, so 2 degrees should get you plenty close.