Three people worked well for the roofing. Here we have four (and my Dad "supervising". You can see some timbers balancing on the peak that later become the observation deck. It took three days to attach purlins and roof. You use self-threading screws with rubber gaskets to attach the roof to the purlins. No pre-drilling needed.

Greg stayed on for the frame but was done before the roofing, siding (skin) and stalls. It was more economical for me to finish the rest myself and he was missing home. One thing that drove him crazy was that I wanted an observation deck on top of my barn. I thought it would be a shame to have such a high building without a good place to sit and watch the stars or survey the property from. To keep things simple, I designed the timbers to sit on top of the completed roof. I used some timberlocks up through the rafters and metal roofing to secure the legs of the observation deck. Its real sturdy and doesn't leak. I built a lid type cover to access the deck from the third floor. So my barn has four floors if you count the observation deck.