Back on the jobsite in the beginning of March, we uncovered the foundation and started framing. We framed the posts like stud walls, on the ground between top and bottom plates, then stood them up. We installed only one doubled 2x6 at each post location—except at the two outside corners—adding the second doubled 2x6 in place later. This reduced the weight of the walls, making them easier to stand up. The second floor was framed using 2x12s at 16 inches on-center, running perpendicular to the house. We used LVL for end joists and doubled it up to serve as a header on the long wall of the sunroom. For bridging at midspan, we used solid 2x12 blocks. Next, we started the roof framing.
We framed the roof using Douglas fir 2x10 rafters, which were doubled up at the hips. We cut the seats so the top of the rafters ran flush into the rim joists; we would add the overhangs later to match the flare of the existing roof. The steep pitches—13:12 at the main roof and 20:12 on the end—required rafter bevel cuts well beyond the 50 degrees our saws would cut. Instead, we cut the inverse bevel on one end of a block that ran between the king common rafter and the hip, then cut the longest jack square to butt up against it. We repeated this with each jack, running a block from the longer adjacent jack to the hip, square-cutting the next jack and installing it against the block. It required a little more material, but saved a lot of time.
We sheathed the new roof with Zip System panels taped at the seams, which we like because they dry in quickly and are easy to walk on.
Where the new sheathing met the existing roof plywood, we fastened a layer of Grace Tri-Flex synthetic underlayment, the same material we would eventually use under the new shingles on the main house. We prefer this material to felt paper because it’s lighter and stronger, it comes in wider rolls, and—especially important in this case—it can be left exposed for up to 6 months without bubbling, curling, or degrading. Since we needed to open the roof in a couple of places while we built dormers, we needed durable weather protection for several weeks. When it came time for roofing, we ran a 36-inch-wide band of Grace Ice and Water Shield at the eaves. At the new roof, we left most of the release paper in place until the applied eaves were installed, then peeled it off and adhered the membrane to the flared sheathing.