The California FHB House Framing in Pictures
Strategic use of engineered lumber and steel connectors in this high-performance home allow for open living spaces while also meeting seismic requirements.
The California Fine Homebuilding House uses advanced-framing principles. A key feature of this framing method is the 24-in. o.c. framing layout, which reduced the amount of framing lumber used—an efficient use of resources—and improved performance by creating more space for interior insulation. Building on an elevated pan deck meant that the walls and roof were framed before going to back to frame, insulate, and sheath the first floor. TJIs were used liberally not only to span large, open spaces but to create deep floor and roof bays for the thick insulation needed to reach Passive House performance levels.
View the SLIDESHOW below for a detailed account of how this house’s structure went together.
More from the 2018 FHB House project:
- Why Do Most Passive House Projects Use European Windows?
- Installing Rockwool for Continuous Exterior Insulation
- Air-Sealing a High-Performance House
Framing started with the garage. It’s essentially a bank barn, with car parking on the upper level and shop space below. This main beam will carry the floor-framing load with a single post below.
After the main girder was rolled in place, 11 7/8-inch Trus Joist TJIs were set, and the floor was sheathed with AdvanTech subfloor.
Once the elevated slab had been poured, the framing of the house could begin. Portions of the slab that are close to grade have curbs to prevent water from getting between the floor and the wall framing. Elevated sections of the slab, where water infiltration isn’t a concern, are flat right up to the edge. Because of the changes in grade and floor level, there are three plate heights for the first-floor walls in the house.
The framing is out of sequence from a typical platform-framed house. The walls and roof are framed before the first floor because mechanicals and insulation need to be installed before the floor is sheathed. The floor over the mechanical room in this photo is temporary while the walls are framed, since the height of the floor framing is above the slab level.
Wall plates are typically made from pressure-treated lumber because their proximity to the damp concrete foundation puts them at risk for rot or mold growth. The plates in this house were wrapped with flashing tape as a capillary break, so the builder was able to make them out of conventional framing lumber.
The long south wall was raised with wall jacks and then straightened.
The house is in the same seismic zone as San Francisco, which required that every exterior wall (and a few interior ones as well) were built as sheer walls. In addition to the standard J-bolts, there are lots of Simpson Strong-Tie holdowns like this one. They are used to tie the house to the foundation and also to tie the second-story floor system to the first-story wall assembly.
The second-floor system in the center of the house is framed with Trus-Joist TJIs and Simpson Strong-Tie hardware to reinforce the cantilevered overhang.
The second-floor deck relies on AdvanTech subfloor and subfloor adhesive for a squeak-free finished floor.
Once the walls were raised, a TJI off-cut was used as a guide for setting the Simpson Strong-Tie hangers for the TJI rafters.
The Trus-Joist rafters provide plenty of depth for insulation, span the width of the room to create a large open space, and are light enough to be moved by a single carpenter.
The walls and roof are both framed 24 in. o.c. so that rafters stack directly over the studs for a continuous load path.
A cant strip at the top of the wall sets the low-slope roof angle for the rafters.
Second-story wall framing moved forward at the same time that first-floor rafters were going in.
The builder chose to frame rough openings in the wall with Weyerhaeuser’s TimberStrand engineered studs because they are superstraight. The TimberStrand 2x6s were also used for the plates because they make for a straighter wall with fewer splices.
Where the breezeway roof connects to the garage, the ledger can be attached directly to the wall because the garage and breezeway are unconditioned space.
Where overhangs and roofs over unconditioned space (as on the porch shown here) connect to the house, Maine Deck Brackets are used to reduce thermal bridging and allow continuous insulation on the exterior of the house walls.
The porch roof is also framed with TJIs. This deep porch on the west end of the house provides an outdoor dining area and solar shading to control heat gain in the house.
Once the walls and roof are complete, the floor can be framed over the slab. The deep TJIs over 4×4 sleepers allow for lots of insulation.
After mechanicals were run and the joist bays insulated, the AdvanTech subfloor was glued and nailed.