Floor joists: step by step

In a previous post I discussed my ideas about how to cut a dovetail tenon and the arc I planned for the floor joists. At that point in time, all I had done was to try out my ideas with the portable band saw. Last Wednesday, August 15, Mark the Intern and I began putting my ideas into action on the floor joists. The frame has 33 first floor joists, 26 second floor joists, and 37 purlins. All of these are cut from 12 foot oak 4"x6"s. We started with the first floor joists since these wouldn't be seen. This gave us 33 to practice on. As I've mentioned earlier, we are only going to have one end completed before the raising. Once the frame is up, we can measure to make sure that the floor joists and purlins are the correct length. Some beams and rafters have a little bow to them and all the timbers' actual measurements don't correspond exactly with their nominal measurements.

Here are the steps we took for cutting the dovetail tenons and decorative arches on the joists and purlins:

First, we have the 4"x6"s in the garage on the saw horses. We worked with four at a time because this amount gave us enough room to move them around and work on them.

For the second-floor joists and the purlins, we planed the visible surfaces. We were able to run the two vertical sides through my 12" Powermatic planer, but because it can plane a 5" maximum thickness, we had to plane the bottom of each by hand. We didn't plane the first-floor joists because they won't be visible from inside the house. (Yes, that's me in the picture.)

After planing the joists/purlins, we marked and cut one end square. The other end will be cut square at the time it is finished. The next step was to mark the dovetail and the arc on the end using the templates I had previously made.

Once the end was marked, we cut the bottom of the tenon with the circular saw. We also cut across the bottom of the joist on the line next to the arc.

After making these two cuts with the circular saw, we knocked out the square at the bottom of the joist along the underside of the tenon and in front of the arc. The portable band saw doesn't have a deep enough throat to cut the arc without removing this block of wood.

Using the portable band saw, we next cut the arc. It's quite easy to cut this crooked until you get a feel for the saw as one side or the other cuts higher, lower, faster, or slower than the other side. It wasn't critical on the first-floor joists since they won't be seen. So, that gave us 33 to practice on.

After cutting the arc, we used the circular saw to cut the shoulders of the dovetail to the correct depth, and then we used the band saw to cut the angle from the corner to the shoulder.

After completing all these steps several times, we had a stack of floor joists ready for raising day.