Exterior Rake Crown Moulding with 3 Different Crown Moulding Profiles

The proper way of installing exterior rake crown moulding is with three different crown moulding profiles.(Source: Gary Katz) One for the level-horizontal crown moulding at the bottom of the rake, one for the rake and one for the crown return at the top. The main difference between Rake Crown Moulding with Three Different Profiles and Rake Crown Mouldings with No Transitions is the crown projection from the vertical wall. Both styles have crown mouldings that have different spring angles as each face is turned in a vertical or horizontal plane. The second difference is the crown moulding profile. With Rake Crown Mouldings with No Transitions, mainly meant for interior MDF crown moulding, there's only one crown moulding profile. The exterior gable rake crown moulding with different profiles can use 2 or 3 different crown moulding profiles.

Spring Angle
Degrees input: use any crown spring angle in degrees like 38.00°

Roof Slope Angle
This is the roof slope angle of the building. See below for typical roof slope angles. This is measured in the vertical plane. An 8:12 roof pitch is = 33.69007° You can enter 33.69007° or the total vertical plane angle as 123.69007° (90° + 33.69007° = 123.69007°) Use your angle finder if you don't know the roof slope angle. The Wall Corner Angle Must be at 90° to calculate the correct Roof Slope Angle.

Back width of Crown Moulding
This would be the Face A back with of the crown moulding. The calculator will print out the dimensions of the other two crown mouldings based on the back width of Face A.

Calculated Results for the Crown Molding Angles.

Crown Miter Angle for material laying flat in compound miter saw
Crown Saw Blade Bevel Angle for material laying flat in compound miter saw

Calculate Spring Angle.
Use the Spring Angle Calculator to enter the rise and run of the crown molding to calculate the spring angle for the crown molding your using.

Online Link to
Rake Crown Moulding Geometry

Roof Pitch in Inches per Rise of Roof in 1 Foot of Run -- Roof Slope Angles

0.5:12 = 2.38594°
1:12 = 4.76364°
1.5:12 = 7.12502°
2:12 = 9.46232°
2.5:12 = 11.76829°
3:12 = 14.03624°
3.5:12 = 16.26020°
4:12 = 18.43495°
4.5:12 = 20.55605°
5:12 = 22.61986°
5.5:12 = 24.62356°
6:12 = 26.56505°
6.5:12 = 28.44293°
7:12 = 30.25644°
7.5:12 = 32.00538°
8:12 = 33.69007°
8.5:12 = 35.31121°
9:12 = 36.86990°
9.5:12 = 38.36749°
10:12 = 39.80557°
10.5:12 = 41.18593°
11:12 = 42.51045°
11.5:12 = 43.78112°
12:12 = 45.00000°
12.5:12 = 46.16914°
13:12 = 47.29061°
13.5:12 = 48.36646°
14:12 = 49.39871°
14.5:12 = 50.38931°
15:12 = 51.34019°
15.5:12 = 52.25319°
16:12 = 53.13010°
16.5:12 = 53.97263°
17:12 = 54.78241°
17.5:12 = 55.56101°
18:12 = 56.30993°
18.5:12 = 57.03060°
19:12 = 57.72436°
19.5:12 = 58.39250°
20:12 = 59.03624°
20.5:12 = 59.65675°
21:12 = 60.25512°
21.5:12 = 60.83239°
22:12 = 61.38954°
22.5:12 = 61.92751°
23:12 = 62.44719°
23.5:12 = 62.94940°
24:12 = 63.43495°