As the insulation fell away and the existing framing was exposed, the trouble mentioned earlier found us. When the addition had been built, a structural valley had been added to just one side. The valley framing on the other side was a hybrid, with a structural valley meeting a doubled rafter, and a "California valley"—with one roof resting on the other—continuing the rest of the way.
The builder had then suspended the ceiling-joist support beam from the rafters above using vertical 1x6s. The problem was compounded by the fact that both ridges were non-structural. These techniques were right out of the Rube Goldberg school of home building.
The framers inserted a post to support the existing triple 2x8 valley as well as the new structural ridge. They continued the post down through the wall framing below, and down into the crawlspace, where we poured a footing to pick up the point load. The framers also removed the section of original roof framing that continued under the roof of the addition; this exposed the entire length of the valley from below.
With the roof supported, all the original ceiling joists were taken out and the old roof at the valley supported temporarily with vertical 2x4s until a new double 2x10 valley was in place between the ridge and the inside corner of the ell.
My goal was to keep the original unvented roof intact, so for insulation, we decided to use 10 inches of spray foam to give us the required ceiling R-value without venting. To get enough depth, 2x10 rafters were sistered onto each of the original 2x6 rafters, using framing nails and Timberloks.
Jack rafters were either sistered or added as needed along both valleys. To deal with uplift issues without opening up the roof, 2x4 collar ties were used to join each pair of rafters. The ties gave the ceiling a flat section at the top, but the clients were fine with that compromise, and it gave the electricians a level place to mount the ceiling fan.
With all the new rafters in place and both ends of the ridge supported on posts, the crew ran furring strips over the whole ceiling and filled in the framing above the bathroom walls and over the flat ceiling.