We used round poles harvested on campus for the roof rafters. We flattened one surface of the poles, on which the roof will lie, and then scribed (traced) two cuts on the opposite sides for the rafter to attach snugly to the timber frame beams.
To do that, we first laid out vertical and horizontal coordinate lines on the ends of the poles. We measured 1/4″ down from the vertical point and drew a level line there. We snapped these lines with chalk along the length of the pole. (We found that snapping the string in the same plane as the drawn line resulted in a more level surface than snapping the string perpendicular. This is because any bumps and valleys in the pole will distort the string when it is snapped perpendicularly.) We then measured 5.5″ down from the 1/4″ line and snapped that line also. This line defines what the depth will be of the joint with the timber beam.
Using hand saws and chisels we removed the top 1/4″ from the poles.
We lifted the poles on the timber frame and there we traced the cuts where the poles will sit on the beams. We used a simple method called “block scribing”. We measured the height from the timber frame to the 5.5″ layout line on the pole (at the lower edge of the joint.) We measured on both sides of the pole, making sure that this height was the same on both sides.
Then we took a level block of wood of that same height (say, 1″) and placed it on the beam, parallel to the pole. We drew a line on the pole, tracing across the top of the wooden block.
Then we traced the width of the cut along the inner and outer edges of where the pole overlaps the beam.
Then we cut out the traced area with hand saws and chisels.
In this last photo, you can also see that we added one additional post for support on the front wall, to the right of the door opening. That right side of the front wall will be almost all glass.