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  • Writer's pictureJim Martin


The marking out of rafters is another excellent opportunity to dust off some of the old math skills. Simple rafters like these are a tour-de-force of the right triangle. My old geometry teacher would have been all over it.

So, after all my pontificating about Pythagoras, I have to confess... the rafters themselves were so small, and the distances in question so relatively short, I opted for the brute-force method. I cut a 2x4 roughly to length. Jenna and I held a 2x4 in place, and I marked off the angled cut at the ridge, then what get's called the bird's mouth cut at the other end. I made these cuts and test fit the rafter. After one more set of slight adjustments, the rafter fit well on both sides of the gable end of the house. We were ready to go!

If you want more specifics in how to lay out rafters that are too big for the brute-force method, here's a great ~8 min YouTube explanation. It offers a basic primer on different ways to measure the pitch of the roof, how to use a speed square (another favorite tool, though not nearly so ancient) to mark out the rafter, and several other helpful things.The Perkins Builder Brothers are great in general--goofy, knowledgeable, super clear, and helpful. And, in the rafter video at least, one of the brothers sports quite the hat.

For my process, once I had one rafter that fit, I used it as a pattern to mark out the remaining rafters. I used the chop saw for the angled cut at the top. For the bird's mouth cut, I started with my circular saw set to max depth of cut, then finished with a hand saw.

Here we are getting started on the first few sets of rafters over the kitchen. (I must be taking a break here...)

Oh, baby. Looking more and more like a tiny house every day! Again, I'm using a combination of framing nail gun and three inch decking screws to secure the rafters. But because it's a tiny house and will be hauled around at least a few times, the house needs to be prepared for high winds. So, some hurricane strapping is coming later.

Here's the first set of rafters completed! This forms the cathedral ceiling (more like a chapel ceiling in a tiny house, I guess) over the kitchen and living room. (I must be taking another break...)

There are all these little joys along the way. I mentioned the joy of standing on the deck of the project and surveying your handiwork. Another is what happens when you get enough plywood on the structure so that when you step inside, you actually feel like you are inside of something. Your voice sounds different as it comes back to you from the walls you built. Small but meaningful joys, indeed! Not unlike the feeling of sitting in your very first car with your very first full tank of gas. (Okay, that last part is a shameless plug for some of the posts I've been putting up about my own very first car, The Beloved Corona. That series is sort of the origin story of how I became a tinkerer--someone who might some day decide to build a tiny house.)

If you look closely in this picture you'll see the plumb bob hanging from the first rafter (down past the kitchen window). The plumb bob is employed here by the same process and for the same reason. We need to make sure the rafters are sitting in the same plane as the studs they are set up over. That helps us keep the roof square so all the plywood sheets fit correctly. In this case I was just a little off. The plumb bob is hanging to the right of the mark. When I install the first sheet of roofing plywood, I will use it to wrack the rafters back in shape and bring the bob over the mark. More on that later.

The pitch of the roof over the loft changes to allow for a bit more headroom. So, of course, that requires a completely different set of rafters. Truth be told, I used the brute force method to cut this set to size as well. Here is what the transition looks like:

And, as usual, Bear is keeping a close watch on the progress.

In this final photo you can see almost all the rafters are in. The next step will be to frame out the loft which will serve as the "floor" underneath that last set of rafters. In this picture you can also see the trapezoid that will be the floor underneath the 2' bump out section. That will be bolted down to the hitch, and will support the center section of the cantilevered loft extension.

Again, with rain in the forecast, we had to pull the sheet of plastic back over everything. It's staying reasonably dry, but I can already see a piece of plywood sheathing that's warped enough that I'll probably have to replace it. I can't wait until we're dried in!

Bear is fascinated.

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