A comprehensive educational community devoted to trim carpentry, finish carpentry and architectural millwork. Hosted by nationally recognized author and finish carpentry specialist Gary M. Katz.
Rake Crown
Crown molding is milled with profiles and fillets that meet at right angles. Those fillets are supposed to be plumb and level. The relationship between the spring angle of the crown and the profile face is meant to accomplish that. That means, to install crown on a raked ceiling, multiple sizes of the same profile are required to change two planes simultaneuosly: The horizontal crown must be taller than the raked crown in order for the rake crown to resolve with the horizontal crown. I'm sure there's a mathematical forumla that defines that size ratio, and I'm sure I'd never understand it. If it weren't for Joe Fusco's patience, I wouldn't understand the concept of two planes changing in one corner. But I do know that open pediments are the best place to spot custom crown sizes used to resolve the problem with rake crown changing two planes simultaneously.
I used to think that the lower corner of an open pediment should also have two sizes of crown. I also thought that this photo, taken from the exterior of a home in Providence, RI, was a good example of lazy carpentry: cutting the bottom of the rake square to the pitch makes it easy to return the crown, but the crown is not 'plumb.' If the crown was plumb, the corner would be plumb and elongated.
I started rethinking that judgement after a recent trip to Denver, where Mike Sloggatt and I toured the Molly Brown Mansion (not really much of a mansion, but the barge rafter details were very cool). Both of us looked right at the crown and said, "HEY! They Cheated! They cut the rafter tails off square, instead of making plumbcuts, so the crown turns the corners!"
Here's the other side of the front bowed bay and barge rafter.
When you look closely at this crown, you realize the decision to cut the rafter tails square wasn't done lightly but intentionally--the crown on the horizontal eaves would have been huge and out of scale with the home had they done otherwise, especially with this steep pitch roof.

So I came home from that trip and starting looking closer--how else do we ever learn anything. It's the close look that counts.

This Georgian mantelpiece, from the Humphrey Sommers home in Charleston, SC, is one place I looked closer.


Here you can see the plumb cut at the top of the pediment, and the square cut at the bottom--which made it much easier to turn the lower corners, but also enabled the carpenter to use the same size crown all the way down the rake and around the pilaster break. If the carpenter had created a plumb cut at the bottom of the rake, the symmetry of the mantel probably would have suffered from 'fancy joinery.' This way, the two nearby outside corners--one on the lower pediment and one on the left side of the break around the pilaster--are symmetrical.

Here's another example, from the same period, a Georgian mantelpiece from Drayton Hall. The carpenters did the same thing: Plumb-cut the upper corner and square cut the lower.
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