Next up, we assembled the fascia trim as four-sided boxes, which we would later lift into place. As careful as we were with the assembly, we struggled to maintain an exact alignment when joining the miters. It was critical when joining these corners to keep the highly visible 1/4-inch lip on the side panels aligned (in some instances, we compromised on the alignment of the 2x2 and bullnose to achieve this).
Each fascia consisted of three visible pieces: the 1x8 side panel, a 2x2 “cornice,” and a 1x3 bullnose cap over the cornice. A fourth piece—a bevel strip dadoed into the cap—was added to direct the LEDs toward the ceiling. For the side panels, Cregg plowed 5/16 inch of material out of the back of them in two passes on a 12-inch jointer. He left the bottom 1/4 inch of the boards intact, creating a lip that would overlap the bottom grid and cover the joint between sides and bottom. In addition, because much of our wider, 1x8 cherry stock was lightly cupped, we ran parallel saw kerfs on the back, allowing us to force the boards flat when joined at the corners.
A site-built jig was used to accurately align the 2x2 cornice on the 1x8 side panel. We glued and screwed the 2x2 from the back. Later, we glued and screwed the bullnose piece from the top and then the bevel strip (cut from scrap mahogany) was glued into the dado and wouldn’t be visible from the floor.
In addition to the cupped wood, we found that the 12-inch Bosch miter saw we were using for the miter cuts flexed across its armature, throwing the cuts up to 2 degrees out of true. Once this was diagnosed, I overcame the problem by applying a little opposing force as I cut. Since we couldn’t re-trim the pieces without throwing off our tightly held dimensional tolerances, and starting over would have been enormously costly, we had to proceed with them as is; nearly every joint was a trial.
We’d also installed splines across the miters to restrain future movement. I cut the spline grooves on a sliding miter saw in two passes to get the 3/16-inch width required, using the saw’s depth stop to limit the cut. We cut cherry splines on a table saw, keeping the grain oriented perpendicular to the joint. To ensure a straight cut across cupped boards, I clamped them flat to the sliding miter saw bed and pulled the blade across at a 45-degree tilt.
We then used Clam Clamps and Maestro M1201 spring clamps to join the mitered corners of the individual units. The clamps were essential because the corner joints of the fascia boxes were extremely difficult to pull together.
We installed lots of trim-head screws, along with glue, to hold the joint together.
We sanded the fascia boxes with a Festool finishing sander prior to installing.