Since the theatre would have two rows of seating it was essential that the back row be on a riser. Using a few different formulas I calculated that the riser would need to be a minimum of 13″. The final dimensions would be 10’x6’x13″.
I used 2″x12″s for the frame and 2 layers of 3/4″ plywood for the surface. The only reason I doubled up on the layers was to gain that extra 3/4″. Once the underlay and the carpet were installed I would have my 13″ minimum height.
I really had to rush the build on this since the carpet install was already scheduled. I finished construction of the riser at 3am the night before the carpet would go in.