Cutting Hip Rafters
When cutting hip rafters I prefer to cut them one at a time, because of the size and complexity, gang cutting is impossible.
If you are not already familiar with the parts of a hip roof feel free to click on the link which will take you to a page showing the components and their placement position.
The first step is to find the hip rafter length and select the appropriate length and size of lumber. Hips are usually one size bigger than the common rafter stock.
I prefer to only load one hip on the cutting horses at a time and cut them individually because of their size and the complexity of the layout procedure.
When using a framing square hold the tongue on the pitch of roof and body on 17 inches for all plumb and level cuts.
If using a big 12 speed square make sure to hold it on the Hip/Val marks for the pitch.
Layout and Cut the Hips
Cutting hip rafters is easiest if you lay them out and cut them as you go to make them easier to measure.
Begin by standing the rafter stock on edge with the crown facing up. Start on the end that will be the top or plumb cut.
Using a speed square near one end make a 90 degree mark and also mark the center. This will be the long point of the plumb cut.
Next lay the rafter down with the crown away from you and mark the plumb cut on the side of the rafter. Then flip the rafter over and mark the other side.
Make two 45 degree lines from the center mark to the outer edge towards the tail. This outer edge will be the top of your plumb cut
Make the Plumb Cuts
Set the saw for a 45 degree cheek cut and make the cut on one side of the rafter, then flip it over and cut the other side.
One cut will have to be made from the top of the rafter and the other from the bottom.
After you are all done with the plumb cut it should look like the three photos to the right.
Measure and Mark Rafter Length & Tail
Stand the rafter on edge with the crown facing up and hook a tape measure on the long point of the plumb cut and mark the length to the backside of the birds mouth.
Next measure and mark the amount needed for the tail. Now make two 45 degree lines from the center and back up towards the top plumb cut. These will be plumb cuts for the tail.
Now is the time to flip the rafter back on the side and layout the birds mouth. I lay the rafter out with the same stand as a common rafter.
In order for the jack rafters to plane properly we must reduce the stand of the hip. For more on this please see the dropping hip rafters page.
We can now go ahead and with the saw set at 90 degrees cut the birds mouth. The level part of this cut needs to be accurate but I always over cut the backside of the birds mouth (an inch or even two) to allow it to fit the outside corner better
Next is to layout and make the tail cuts with your saw set at a 45 degree angle, as with the top cut one will have to be made from the top and the other from the bottom.
You should also make a level cut high enough that it will not hang below the fascia line.
Tips on Cutting Hip Rafters
- Use 17 inches on the body of the framing square and the roof pitch on the tongue.
- If the building is out of square all four hips will be different.
- You must reduce the stand or the jack rafters will be off.
Links to Related Carpentry Pro Framer Pages