So the oldest portion of our personal Xanadu is slated to become a solarium like space with exposed beams, double height cathedral ceilings and lots of light. Upon closer inspection it became obvious that our future solarium was mimicking a somewhat inebriated lean, the architectural equivalent of hanging loose. At some point many years past when they installed the North facing dormer they did so by just cutting through the center rafter, lacking the parallel pressures to hold things in line our walls have started to push out. Not a huge amount, but it's probably good that the chimneys are there to serve as a supportive friend. We had an engineer come in to review our plans and to determine if taking out the floor (not beams) would exacerbate the issue, and whether our plan to use steel turnbuckles to pull everything back true would work. To our surprise he said forget about pulling things back, it would probably cause more problems and that all we needed to so was add some braces up high to hold things together as they currently stand. So with that in mind we found some age appropriate lumber (since the ties will be exposed) and installed them up high.
Here you can see Graham's favorite tool, the Bostitch framing nailer and a couple of the ties. We measured the angle of the roof and cut the ties to match. We use the framing nailer to tack them in place.
Once the ties were in place we drilled pilot holes and then really tied them all together using long screws. We opted to use screws instead of just nails since they will be able to grip better and we expect the roof will flex a bit over the years. The rafters are all tree trunks dating back to the 1700's, amazing how well they have held up. We would love to leave them exposed, the need to have insulation trumped aesthetics this time around.