Valley Rafter task Model

Testing the Roof Framing Geometry Propositions – Axioms on a under purlin with lip cut, lower claw, intersecting a valley rafter. The Roof Framing Geometry Propositions – Axioms work on a purlin rafter to valley rafter, however the geometric lines are reversed for the upper and lower claw lines on the purlin rafter that intersects a hip rafter. 

Notes:

1. The Valley Rafter Claw Line,Bottom Edge of the Valley Rafter, Planes with the Top Edge of the Purlin Rafter.
2. Intersection of Valley Rafter Foot Print Line & Extended  Purlin Rafter Top Edge Plane Line defines the Valley Rafter Claw Line.

Drawing with a purlin intersecting a hip rafter and valley rafter.

Roof Framing Geometry Proposition – Axioms # 10:
The intersections of the valley rafter roof surface line, at the foot of the valley rafter, and the profile rafter foot print line defines the valley rafter claw line for the upper claw lines on jack rafters.

Roof Framing Geometry Proposition – Axioms # 11:
The intersections of the valley rafter foot print line and the top of the purlin rafter top edge plane line defines the valley rafter claw line for the lower claw line on purlin rafters.

Verkanteter Gratsparren Axiom # 9

After looking at a 37 page solution to the jack rafter claw angles in a PDF file designed by a German Trainer for the World Skills Carpentry Competition, I'm adding a new Roof Framing Propositions – Axiom that applies to hip rafters rotated into the roof surface. This Axiom should eliminate a couple of the geometric steps to draw out the lower claw lines for jack rafters that are plumb to the earth. The  German Trainer's task model has the Verkanteter Gratsparren, canted hip rafter, with the jack rafters lower claw geometric development. His geometric development for the lower claw lines wasn't understandable, maybe because I don't understand some of the German Zimmerman drawing techniques yet. However, this Axiom should make it easier to draw out the lower claws lines for jack rafters no matter what  language you speak or read.

Roof Framing Geometry Proposition – Axioms # 9:
If the hip rafter foot print line is parallel to the jack rafter run line, then the lower claw line for the jack rafter is parallel to the jack rafter run line.

This Axiom will apply to roofs with an eave angle of 90°, with equal or unequal profile roof slope angles.

If you have Tréteaux Angles for RafterTools+ app for iPhone or Rafter Bevel Angles app with the Tréteaux Angles , you can check your drawings using P17a-DP for the upper claw angle, P16a-DP for the lower claw angle and P18a-DP for the back bevel angle on the top edge of the jack rafter. In this example I entered an Eave Angle of 90°, Main Slope Angle of 55.00798° and an Adjacent Slope Angle of 48.01279°. The hip rafter width does not affect the lower or upper claw angles in the app.

Some of the drawings to develop the DP line of the hip rafter rotated into the roof surface.

Verkanteter Gratsparren DP Line

Drawings showing the development of the DP Line for the Verkanteter Gratsparren, canted hip rafter.

Roof Framing Geometry Proposition – Axioms  # 8:
The intersection of the Rafter Run Line & TC Line locates Hip Rafter DP Line.

Verkanteter Gratsparren

Verkanteter Gratsparren translates to canted hip rafter in German. In these drawings the canted hip rafter is rotated into the roof surface plane on a ground plan with equal roof slope angles and the eave angle is 60°. This example uses my Roof Framing Geometry Propositions – Axioms on a jack rafter that's plumb to the earth and the German Shiften method for locating the upper and lower claw angles from the width of the jack rafter in plan view.

California Valley Sleeper Saw Blade Bevel Angle

On this job, a 1200 square foot addition to an existing house the built in the 1950's the structural engineer called out the 2x beveled sleeper on the plans. This is the first time I've seen a structural engineer call out a beveled California Valley Sleeper.

It's fun to draw out the California Valley Sleeper Bevel Angle using geometry, but on the jobsite you need to know the actual California Valley Sleeper Saw Blade Bevel Angle. You can use one of my iPhone or Android apps to get the California Valley Sleeper Bevel Angle or use trigonometry. The California Valley Sleeper Bevel Angle is 90° minus the sum of the main roof hip rafter backing angle plus the adjacent roof hip rafter backing angle. You also need to know the California Valley Sleeper Bevel offset dimension, to snap a line on the California Valley Sleeper Material.

4:12 Equal Pitched Roof Slope Example:

C5m Main Hip Rafter Backing Angle = 12.92097
C5a Adjacent Hip Rafter Backing Angle = 12.92097

Valley Sleeper Saw Blade Bevel Angle = 90° - (C5m + C5a) = 64.15807

The California Valley Sleeper Bevel offset dimension is:

Material Depth × tan(Valley Sleeper Saw Blade Bevel Angle)

in this example the material thickness is 1.5"

1.5" × tan(64.15807) = 3.09711" or 3 1/8"

In this picture you can see the red snap line on the face of the 2x12 valley sleeper material for the California Valley Sleeper Bevel offset dimension. However, the Valley Sleeper Saw Blade Bevel Angle was greater than the bevel angle settings on my saw, so I use 90° - 64.15807° = 25.84193° or 25.8° and cut the material from the edge of the material instead of using the 64.15807° on the face of the material. First I used my 7 1/4" SkillSaw to cut the bevel angle, then I used my Bigfoot Saw with the 10" blade to finish off the cut. You could also use a Bigfoot saw with a swing table to make the 64.15807° bevel angle on the face of the material. 

California Valley Sleeper with the roof sheathing miter angle on the face of the sleeper and the bevel angle for the plumb cut using the roof slope angle.

The existing house built in the 1950's has California-Okie Valley Framing. 1x8 vrustic for the sleeper, 2x4 jack rafters and 1x4 ridge that's sagging 2" or 3" from the roof spreading apart. 

New 2013 California Valley framing requirements.

Install flat blocking below the new California Valley Sleeper.

Nail off the new roof sheathing at the Shear Wall Schedule nailing pattern. 6" O.C. in this example. Then nail off the valley sleeper material at 6" O.C.  The level cut of the valley jack rafters must be fully supported. For this house it meant using a 2x12 valley sleeper that's beveled and a 2x8 sleeper to support the  level cut of the valley jack rafters.

Install hangers or clips at the ridge and the level cut at the foot of the valley jack rafters.