Sunday, January 25, 2009

Trimming Rafter Tails

The trusses in the main part of the house are attached at the top to the main roof girder. That girder is made up three layers. In theory, the girder should be perfectly straight and a uniform thickness from one end to the other, but in practice it's really not. It bows a bit and bulges in places where there are steel gussets between the layers.

So, even though the trusses are all the same length, the rafter tails that stick out at the front of the house don't all stick out the same amount. They vary by as much as 3/8". Although that's not very much, once the gutter board and fascia are on, the front of the eave would look wavy when you looked up at it.

It's difficult to trim the rafter tails in place, especially when you're only trying to cut such a small amount off the end. The solution was to build a jig that allows me to cut them off with my circular saw.

I measured the last rafter on each end of the house and determined how long the tails should be. Then I measured 5" up from there and snapped a chalk line across the top of all the rafters. (The 5" offset is needed because that's the width of the bottom plate on my saw.)

To trim the tail, I just clamp the jig to the rafter, lining up the front edge of the jig with the chalk line. The side of the jig hangs down the side of the rafter tail. I just run my saw up against the edge of the jig, and it trims the tail to the right length. You can see in the photo below that I've cut about half way through this one, trimming off about 1/4". (Click on the photo to enlarge it.)

Now when I run a string line along the front of the rafter tails, they all line up straight.


  1. are you a carpenter mate?
    didnt know it was all THAT complicated
    thanks for the insight = )

  2. Hello! Not that complicated really. It probably took less time to do the work than to explain it in words. Cheers!

  3. Hey I really like how you are documenting your experience, I follow your blog as I'm building our house at the exact same time as you. Keep up the good work!

  4. Thanks Chris. I appreciate your comment. Have you got any photos?

  5. Lots of photos, I don't have any for the last month or so, maybe I'll take a few more this week.

  6. I'd love to see some photos of your project. If you want, you can email them to me at