There are several ways to calculate irregular hip rafters and jack rafter lengths. I'll cover the most efficient method i've found, which uses the RedX Roof App. Here is what the app will automatically calculate for us:
• Full cut list.
• 3D model of the Hip Rafter and Jack Rafters
• Calculate all Jack Rafter Lengths
• Calculate the Hip Rafter and Jack Rafter saw bevel angles
• Calculate the Hip Rafter backing angles
• Calculate the Hip Rafter offset from the corner of the wall
• Show the wall height difference, or choose to keep both walls at the same height
Below is an example 3d model of corner hip you will be creating
Measurements needed
The measurements we will need to to enter into the app are as follows, We will go into details on all of these later on.
Roof Pitch (or roof angle) 1
Roof Pitch (or roof angle) 2
Facia overhang
The Bottom Run of the common rafter
Jack rafter spacing
Optional Customization
There are many things we can customize like:
• Hip rafter thickness and depth
• Jack rafter thickness and depth
• Facia thickness and depth
• Different fascia overhangs
• Choosing to have different wall heights or keeping them both at the same height
• The depth of the birds mouth cut
3D Viewer
After the inputs, the magic begins. The Hip Rafter Builder will automatically generate an interactive 3D model of the corner hip, offering a detailed visualization that you can pan, zoom, and toggle between 3D and 2D.
Full Cut List
Scrolling down, you'll find a comprehensive cut list, which includes the quantity of required pieces, the material size, the length of the cut, and the use of each part.
Material List
Just below the cut list, there's a material list with all the required lumber.
You'll notice in this list, every component has a Label that will correspond with the label on the top down view (plan view) of the 3d hip rafter builder, along with the quantity, material size, overall length of the component, and the component use.
Viewing Rafter Plans
Each component in the cut list is selectable, selecting one opens up the corresponding rafter plan. You'll notice i've selected the hip rafter in the list. You can choose to view the hip rafter with the rafter plan viewer inside the app or or you export or print the rafter PDF plan.
Hip Rafter Plan Viewer
With the plan viewer you can view all sides of the rafter along with all of its measurements. Below every rafter plan is a list of measurements like total rafter length, saw bevel angle, rafter angle, fascia overhang and more. Selecting any of these measurement will automatically zoom into that measurement on the rafter plan. This helps with understanding all of the measurements.
Hip Rafter Layout
For the hip rafter and fascia boards, you'll see a 'Show Layout' button when pressing it, it will show you where all the jack rafter intersects the main rafter, with the measurements for your layout.
Calculating the Hip Rafter Backing Angle
If you wanted to be fancy and bevel the top of your hip rafter In the list of measurements for the hip rafter, you can press the 'Show Backing Angle' button to view the backing angles for the hip rafter.
Finding the Hip Rafter Offset for Irregular Hip Rafters
With irregular hip rafters the hip offset can be hard to calculate. The RedX Roof App simplifies this by showing you the hip offset measurement from the corner of the wall. The image below shows how the hip offset is calculated and displayed in the app.
Viewing the Jack Rafter Plans
To view all of the jack rafter plans, just select it from the cut list and you'll see the corresponding rafter plan will open up below.
Create a Rafter PDF Plan
If you want to create a pdf plan of the hip rafter or jack rafters it's supper simple, there are 2 main ways to do this.
Option 1 Export 1 Rafter Plan: Press the blue export button in the top right corner of the rafter plan, 3 options will come up, choose to either print, share or save the rafter pdf plan to your photos.
Option 2 Export All Rafter Plans: At the top of the cut list on the right, press the menu button, from here you chan choose to share all rafter plans, print all or save all to your photos.
Viewing the Wall Height Difference
To view the difference in wall heights it's easy, use your finger to pan around to the corner of the 2 walls, to press the "front" button and the app will automatically rotate to the front, from here if you look at the corner of the 2 walls you can zoom in to view the wall height difference.
Lets Go Over The Details
Now that you’ve seen what the app can do let me show you all of the details.
The Measurements You Enter Into The App
View the rafter terminology section below for more information on these terms
- Roof Pitch 1 or Rise From Wall for this first input you can enter either the roof pitch of the first side (blue side) if you know it, or the common rafter rise from the top of the wall to the top of where you'r common rafter will finish.
- Run 1 This is the the horizontal distance from the outside of the wall to where your common rafter ends, this is the run for the first side (blue side).
- Overhang 1 Here you enter the fascia overhang of the first side (blue side), the horizontal distance from the outside of the wall to the inside of the rafter.
- Overhang 2 Enter the fascia overhang for side number 2 (green side)
- Roof Pitch 2 Or Run 2 Here you can enter either the roof pitch of your second roof side (green), or you can enter the run of this second side (the horizontal distance from the outside of the wall to where your common rafter ends for the second side.
- Rafter Height Above Plate or Fascia Drop: Here you can enter either the Rafter Height Above Plate, Or the Fascia Drop Measurement.
- Wall Have Equal Heights Here you choose to wither have different wall heights, or keep both wall to be the same height.
- Rafter Spacing This is the distance from the centre of one rafter to the centre of another rafter.
Rafter Terminology
For more information on all the different rafter terminologies have a look at the in depth tutorial i made here Everything You Need to Know about Rafters: Key Concepts and Terms Explained
Save And Load Jobs
To learn more on how to save and load jobs on the RedX Apps view the in depth tutorial here Saving And Loading Jobs On RedX Apps
Print and Share The Plan
To learn more on how to print and share your jobs on the RedX Apps have a look at the in depth tutorial here Print and Share Plans with RedX Apps
Conclusion
As you can see the RedX Roof App makes it super easy to get every single measurement and rafter detail to build an irregular hip roof or a same pitch hip roof. There are lots of other great features like Valley Builder, Rafter Calculator, Turret Roof Builder, Plywood Angles, Dormer Builder and others...
Do you think this is something that you would use? Let me know in the comments.
Thanks to all of you who made it this far!
