This is quite large umm 36x30x24 or so. The bottom is extremely heavy likely 60 pounds or so for just the bottom the sides are only a few pounds and the top is likely 15 or so with the electronics (T-stat and light ballasts) All in all it weights a ton. No sag or any deflection at all. Baltic birch is very strong ply. 1/2 inch bottom, PVC may sag more. If I was not building for a basking animal I would use PVC with no hesitation.