Get Jiggy with It

The Moundville ladies are preparing the roof and framing the extended edges and corners of the pavilion for roof sheathing!

In order to begin roof joists, blocking was attached using the bypass system off the trusses to give the hangers ample room to grab. This was necessary since the roof geometry is created using the planes of the joists and the connection to the ridge beam to create the inverted plane.

The blocking was installed to follow the string lines setting the roof heights. This allowed the team to mark 16 inches on center to install each joist that meets a truss on both ends. To place each hanger, an off-cut of a 2×8 with the correct, angled cut was used to temporarily place and screw in the hangers according to blocking height and spacing.

Then each joist was field measured and placed into the hanger, checking height obsessively to ensure a flat plane. Once a bay was placed, checked, and rechecked, the joists were nail gunned to the hanger and truss. Blocking was added to keep 16 inch spacing and fix any bowing in the wood.

Once the joists in the center of the bays were completed, there was a new challenge in determining the correct spacing where the joists hit the edge beams or ridge beam. Since the beams intersect the form at an angle, varying based on the tolerance in their placement, measuring along the beam produced too many inaccuracies in keeping the joist spacing and ensuring the boards aren’t skewed.

Jigs were created for each beam similar to the truss in which the slope and skew of the cuts were determined and a sample “joist nub” was used to place the hanger. A 14.5 inch piece of wood was then attached to the side to butt up against the previously placed joist to determine spacing 16 inches on center, perpendicularly from the joist. Another 2×4 was also attached running along the top of the “joist nub” and spacer to keep the correct height. This allowed the team to attach the hangers, place a joist and then adjust if needed based on spacing from the master joist and height along the existing plane and strings.

The edge beam along the short side and the ridge beam involved a similar jig and process with slight alterations to match the difference in angles and cuts.

Now, all of the roof joists are installed except for the two low corners (due to tight space constraints with the scaffolding platform, the ceiling needs to be framed in these areas first). The ridge was the last section to be completed, giving a real sense of the roof shape and profile!

Looking down the ridge as it intersects the middle, diamond truss which shows the two flat planes and their relationship to the overall form.
Seeing the joists framing the ridge from below, inhabiting the structure.

Concurrently, the team worked on building the pieces that will form the soffit. Each soffit “wedge” will attach to the edge beam and continue the differing slopes of the roof and ceiling to meet at a 4 inch edge. These pieces will extend the perimeter of the pavilion while allowing the structure’s edge to get as thin as possible. Due to the 18 inch depth where the joists terminate, each wedge was too deep to be engineered out of 2-by material. Therefore, the arrival of new 3rd-year students and neck-downs brought a week of much needed extra help to laminate plywood with both glue and screws as well as set up an assembly line to cut the wedges out (three of these cuts being angled).

Over 90 wedges were completed with four unique templates for each pavilion edge! The next few weeks will be spent installing them. Check back in for a fully framed soffit and roof (hopefully) soon! Meanwhile, enjoy these action and detail shots of this last month of progress!