Baby’s First Ninety Degree Angle (kinda)

The Moundville Pavilion team finished all structural framing with the completion of the soffit pieces to form the pavilion’s final edge. Although the height for the low ridge and tall corners (at 12 feet and 20 feet respectively) was determined as the most successful in balancing circulation and rest, there was a concern among the consultants and clients that the roof may feel heavy in the site. Terminating the resulting eight-foot structural depth into a four-inch edge is an important element of the design to allow the structure to achieve a certain lightness and elegance, avoiding the feeling of a heavy floating object and emphasizing the openness of the high corners and the ceiling’s “wing-like fold” instead. This was accomplished in attaching plywood pieces to extend the edge past the edge beam and frame the final soffit.

The soffit wedges made during spring neck downs ready for installment!

The task in creating this edge and extending the soffit past both the trusses and the edge beams terminating the joists involved some creative thinking. The soffit wedges created during neck downs (see blog post: Get Jiggy With It) combined the differing slopes of the ceiling and roof with angled cuts along the top and bottom. The face connecting the wedges to the edge beam was angled to attach the wedge perpendicular to the roof joists in order to follow the seams of the plywood roof sheathing. Each side of the pavilion had a unique template and wedge design to account for any discrepancies in edge beam and joist placement along each edge.

Making these wedges during neck downs definitely saved some time, but installing the wedges accounted for its own challenges. Since these soffit pieces are forming the final edge of the pavilion, including the corners at the low and high points, they created a line working to a point that didn’t exist yet. On top of that, the pavilion edges slope in four different directions. As we explained in the previous post (Get Jiggy With It) temporary posts held strings to give a line to work towards. Chalk lines were snapped at 2 foot increments along the roof joists to use a jig to hold the wedges perpendicular to the joists as they are attached. Furring strips of 1-by material was attached the to bottom of the wedges to keep their placement and spacing.

Edge detail showing the face of the soffit wedge attached to the edge beam, with sheathing for the roof and ceiling.
The tip of the wedge is lined up to the string and measures 2.5″, the addition plywood on top and bottom will give it a structural edge right under four inches.

However, the weight of the two laminated plywood pieces measuring almost eighteen inches at one end meant that the wedges would sink the longer they were up. The team didn’t want to nail gun them into place before confirming the corners so temporary 2x4s attached the pieces to multiple roof joists at every third wedge to stiffen the members.

Although time consuming and the cause of quite a few frustrating days, the project team and, more importantly, the clients are extremely happy with what the soffit and resulting thin edge contributes to the overall space. Not only does it extend the boundaries of the roof, but it achieves the lightness and floating quality the design intended.

As the team continued the soffit framing to the low corners, it became very clear that additional framing members needed to stiffen the two way cantilever off of the small trusses. Since the corner of the pavilion extended ten feet past the face of the truss, there were concerns about stiffening the corner enough to prevent sag. Thankfully, our trusty structural engineer, Joe Farrugia, saved the day with a last-minute, 24-hour trip to Hale county to see the structure and work through possible solutions with the team.

Since the corner is acting at as a two-way cantilever, Joe recommended stiffening one edge using a laminated beam of 2, 2x6s that notches into three soffit wedges along one side, This beam could then be used as a stiff element to cantilever the fascia board for the opposite edge. Additional strapping (thanks to Jim Turnipseed and his donation of even more Simpson Strong Tie products) firmly attaches the beam to the soffit wedges, ties each wedge back to its partner roof joist, and connects the entire cantilevered corner of the small trusses to the adjacent truss bays.

Cutting notches in the corner wedges to place the beam into
The laminated, 2×6 beam is strapped into the soffit wedges with a tapered edge that reaches the soffit string that the fascia board can attach to
Additional strapping to connect the cantilevered bay to adjacent truss bay.
The end of the beam is tapered from the ridge to create a 2.5″ inch edge mimicking the soffit pieces, meeting the string where the fascia will attach.
Sketch done with Joe of beam solution at double-cantilevered corners.
The tall corners are framed!
It’s a lot of angles…BUT that corner is a near perfect ninety degrees, just sloping in two directions

Long story short, the wedges are installed, the corners have been framed, and everything is officially strapped and nail gunned into place! The team is very proud of making it to this point and excited to see many excited community members commenting on how they envision using the space. Another donation from Scotch Plywood and a forklift rental from Sunbelt rentals means the plywood for the roof, ridge, and soffit pieces is on the platform and ready to go for the next phase: sheathing and cladding!

During all of this, the project team still tried to balance the design and building processes and completed a full scale, bench mock up to finalize the design and continue to consider locations for seating.