Helical staircase build, part 2.
We went with three layers of 1/2” CDX ply for the core of our stringers, veneered with 1/8” Baltic Birch ply on all sides. Both types have exterior grade glues, and we are using Titebond III wood glue for the laminations, which is also exterior grade. We cut the strips of ply for the laminations an extra 1-1/2” wide and will trim them down to final size after the glue-up to get good edges. We marked a layout on each stud so we’d have a reference for the rise of each stringer as it wrapped around the curve, and glued / clamped / screwed / stapled the laminations together one at a time, staggering the seams in each layer. Bought a bunch of new clamps for this job, and also borrowed a bunch from good friends!