I'm building a 12" high riser for second row seating in a HT room in the basement. The area is around 6ft by 12ft. Currently I plan to have 4x2 treated lumber and vapor barrier for the first layer of wood (laying flat), then will sit 8x2 (laying tall) untreated, and need an extra final layer of 4x2 laying tall before adding the plywood surface.
My question is, does the 4x2 have to sit on top of the 8x2 in parallel or can I run the 4x2 at 90 degrees to it ?
I want to do it like this guy did (but he has different dimension lumber): https://serialstartups.co/wp-content/uploads/home-theater-riser.jpg
..is there anything wrong with that? Every other install I see, that uses multiple layers of lumber, they tend to run the lumber/joists all in the same direction.