## Sunday, September 13, 2015

### Off Angle California Valley Framing

Off Angle California Valley Rafters can be calculated using one of my RafterTools+ apps.

On this house the main roof slope is an 4:12 pitch and the off angle California framing is at an 6:12 pitch. First enter 4:12 for both the Main and Adjacent Roof Pitches, with an Eave Angle of 90°. The calculated results will give you the Main Roof Hip Rafter Slope Angle = 13.26268° and the  Main Roof Hip Rafter Back Angle = 12.92097°.

To calculate the California Jack Rafter Foot Miter Angle and Saw Blade Bevel  Angle for the Off Angle California Valley Framing  can be accomplished by entering an Eave Angle of 45°, Main Roof Slope Angle = 18.43495° (4:12) and Adjacent Roof Slope Angle = 26.56505° (6:12)

Roof Eave Angle = 45°
Main Roof Slope Angle = 18.43495° (4:12)
California Valley Roof Slope Angle = 26.56505° (6:12)

Main Roof Hip Rafter Slope Angle = 13.26268°
Main Roof Hip Rafter Back Angle = 12.92097°

With the RafterTools+  calculated results you get an

Valley Sleeper Saw Blade Bevel Angle = 48.46304°

For the Jack Rafter Foot  Miter Angle you add the California Valley Roof Slope + Main Roof Hip Rafter Slope Angle.

Jack Rafter Foot  Miter Angle = California Valley Roof Slope + Main Roof Hip Rafter Slope Angle
Jack Rafter Foot Miter Angle = 26.56505 + 13.26268 = 39.82775°

For the Saw Blade Bevel Angle used on the Jack Rafter Foot Cut

Saw Blade Bevel Angle at Jack Rafter Foot Miter Cut = Main Roof Hip Rafter Backing Angle
Saw Blade Bevel Angle at Jack Rafter Foot Miter Cut = 12.92097°

The  RafterTools+ has the California Jack Rafter Length Difference  or use the following Trigonometry formulas.

Roof Sheathing Angle = arctan(sin(Jack Rafter Foot  Miter Angle) ÷ tan(Main Roof Hip Rafter Back Angle)
Roof Sheathing Angle = arctan(sin(39.82775) ÷ tan(12.92097) = 70.29288°

California Jack Rafter Length Difference = O.C. Spacing ÷ tan(Roof Sheathing Angle)
California Jack Rafter Length Difference = 24” ÷ tan(70.29288) = 8 5/8"

The Valley Sleeper Miter Angle is not built into the RafterTools+ apps. You can use the following formula for the miter angle at the foot of the Valley Sleeper.

Valley Sleeper Miter Angle = arccos( cos(Sheathing Angle Angle) × cos(Jack Rafter Miter Angle at Foot))
Valley Sleeper Miter Angle = arccos( cos(70.29286°) × cos(39.82772°)) = 74.99102°

With a Valley Sleeper Saw Blade Bevel Angle of 48.46304°, you can use this formula for the snap line dimension on the Valley Sleeper for the edge bevel.

Edge bevel width = Valley Sleeper Thickness / tan(Valley Sleeper Saw Blade Bevel Angle)
1.69323 = 1.5 x tan(48.46304°)
or 1 11/16" = 1.5 x tan(48.46304°)

Set the saw bevel angle to 48.46304° for the Valley Sleeper edge bevel.

After you have edge beveled the valley sleeper you can use the Valley Sleeper Miter Angle (74.99102°) for the Valley Sleeper foot cut.

This porch has trusses and I aligned the valley sleeper with the edge of the truss for the location of the valley sleeper.

The ridge cut has a 4:17 miter angle to set on top of the main roof valley rafter. I scribed the miter angle for the valley sleepers at the peak.

For the Off Angle California Valley Jack Rafters I laid out the 6:12 level cut, then used the 39.82 angle for the Jack Rafter Foot Miter Angle.

For the Off Angle California Valley Jack Rafters length difference I used the 8 5/8"  from the RafterTools+app.

The extra blocks at the ridge are for a CS14 strap that runs the full length of the roof. The second row of blocks are for plywood sheathing edge nailing.

1. Richard BirchSeptember 18, 2015 at 7:49 AM

Sim,

Nice Job!

I Deleted previous comments, . . . not really useful. Answered my own questions, I think.

Aproaching things a little different . . .

Once you have the Off Angle Valley Sheathing Angles: Main (28.5°) Lay-Over (19.7°)

And the (Main) Regular Sheathing Angle: For the 4/12, (46.51°)

CLO Valley Board Head Miter Angle is the Regular Sheathing Cut Angle for the Main Pitch Minus the Main Sheathing Angle. i.e. (46.51° - 28.5° = 18.0°)
Foot Miter Angle is Sum of The Reg H/V Sheathing Angle plus the Main Sheathing Angle: i.e. (28.5° + 46.51° = 75.0°)

And . . .

Since both the CLO Ridge and Jacks land on Regular H/V Plan-view angles it stands to reason that . . .

Head-Cut and Foot-Cut Bevel Angles are the same, the Regular Backing Angle for the Main Pitch. Regular 4/12 H/V Backing Bevel, (12.92°)

( . . . which is the same beves used on the Jack's Foot cuts.)

1. Good logic Richard on using the regular sheathing angle to calculate the CLO Valley head and foot cut.

2. thanx, but very little about 6/12 roof pitch, check here http://myrooff.com/6-12-roof-pitch/

3. Thanks but very little about 6/12 roof pitch example, check here https://roofgenius.com/6_12_roof_pitch.asp