I then snapped a line 4 inches in from the edge of the uphill timbers. Measuring across to the downhill timbers, I snapped a second, parallel line. These parallel lines, marked out on both sets of runners, served as reference points.
We laid out the trusses along the snapped lines and nailed 2x4 blocks perpendicular to the lines to serve as stops for the trusses to bump against as we set them.
Since the smaller (20x20) roof was built several feet from a new garage, we braced the first gable truss to that.
Then we set the remaining trusses using Simpson's Spacer Bracers (strongtie.com) at three points along the top chord . We aligned the end of each bottom chord 8 inches from the snapped line on the uphill timbers.
We checked for plumb and verified the on-center layout, then nailed on the lateral bracing required by the truss manufacturer (5).Down the middle, I nailed two 2x6 catwalks to facilitate blowing in loose-fill insulation. We also stiffened the assembly by nailing on 2x6s 2 feet in and parallel to the ends of the trusses.
I laid the sheathing out from the peak down, which left a 20-inch opening at the bottom of the smaller roof, giving us a grab hole to move the airborne roof into place, as well as allowing room for fastening the trusses to the top plate. Starting 20 inches up from the sub-fascia, we nailed on the first course of 5/8-inch plywood sheathing. When we got to the top, we reversed course and shingled from the top down.
Since roofline trim would be installed when the house was clapboarded, I tacked on spacer blocks that simulated the width of the rake trim and eaves fascia before running the drip edge, which was nailed in place as we shingled.
The first course of shingles was nailed at the top so we could slip the last course from the next layout group under it before nailing off that course. We repeated the process until we were within a course of the opening at the eaves.
On roof-raising day, two cranes arrived at 8 a.m.; one small (10 tons) to set the steel rails, the larger (40 tons) to do the heavy lifting. Spectators came as well. Though this home is in the country, neighbors with digital camcorders appeared and passing vehicles slowed to a crawl so that drivers could watch.
The big roof would be set first. Two steel I-beams carried its nearly 3-ton weight. Rigging this roof took three hours, setting it only 30 minutes.
We had allowed ¼-inch clearance on either side of the wall framing for wiggle room. With two tag lines, we placed the roof with little effort.
The smaller roof was hoisted on two 8-inch round pipes. Probably due to its lighter weight (less than 1 1/2 tons), this roof dodged back and forth before settling down.