You have to take long steel poles and a temporary beam in the center! Then jack the center back to level all the while use your comealongs to pull in the sides! After you bring the sides in and the centers raised install new collar framing to tie it together! Install new supports back to the center! She should stay together!
The ridge-line bellying down is not always indicative of the center supports being low, it is rather the eve sides being low. If the gable ends are relatively where they were designed to be, and the sides of the building sag, the top plates (where the rafters are attached) sag as well. This changes the angle of the rafters as well as lowers where they meet at the ridge pole. Sometimes just raising those low sides back to level also straightens the ridge-line.
We are in the middle of trying to do that now to an old barn . Not the same design or height that you have there now but the 4' walls are sitting on top of 8" cinderblock walls that were probably installed when the bottom of the original wood walls rotted out many years ago. The 4' walls are leaning outward 3-4" and we are trying to ratchet the walls back in but need a few more ratchets and cables to do that.
Yes, this is what I did on an old barn with lig rafters. I built a temporary floor across the beams at the top and then put a large beam against the underside point of the roof. I screwed boards together for the beam with the center board sticking up so it could get where the two rafter met. Then I jacked away to make it better. Then I used string in an x across the whole roof. If the string touches in the middle you have four points that are on the same plane. I sistered boards to the logs. There a lot of other tricks too.
You have to take long steel poles and a temporary beam in the center! Then jack the center back to level all the while use your comealongs to pull in the sides! After you bring the sides in and the centers raised install new collar framing to tie it together! Install new supports back to the center! She should stay together!
Thanks for posting this - insightful!
The ridge-line bellying down is not always indicative of the center supports being low, it is rather the eve sides being low. If the gable ends are relatively where they were designed to be, and the sides of the building sag, the top plates (where the rafters are attached) sag as well. This changes the angle of the rafters as well as lowers where they meet at the ridge pole. Sometimes just raising those low sides back to level also straightens the ridge-line.
We are in the middle of trying to do that now to an old barn . Not the same design or height that you have there now but the 4' walls are sitting on top of 8" cinderblock walls that were probably installed when the bottom of the original wood walls rotted out many years ago. The 4' walls are leaning outward 3-4" and we are trying to ratchet the walls back in but need a few more ratchets and cables to do that.
Would it help to jack the ridge up while you’re pulling the rafters together?
Yes, this is what I did on an old barn with lig rafters. I built a temporary floor across the beams at the top and then put a large beam against the underside point of the roof. I screwed boards together for the beam with the center board sticking up so it could get where the two rafter met. Then I jacked away to make it better. Then I used string in an x across the whole roof. If the string touches in the middle you have four points that are on the same plane. I sistered boards to the logs. There a lot of other tricks too.
Thanks Mark