I'm building a bench that measures 23" wide by 96" long, and I'm planning to use 3/4" ACX sanded plywood for the seating surface. My concern is whether this plywood will sag without any horizontal center supports in place, especially when it could potentially hold the weight of 3 adults or 6 children at once. I have to avoid horizontal supports under the bench because of the unique design and usage requirements, so I'm wondering if I should consider adding a frame to the underside of the plywood for extra support, even though that might increase the weight and make it harder to open the hinged bench. What do you think?
1 Answer
Yeah, I think it’s definitely going to sag without any sort of support in the middle. Just carrying a sheet of plywood that big already shows some flex, so adding a load of about 600 pounds (like three adults or a bunch of kids) isn’t going to help! You might want to reconsider how you can support it without blocking your access below. Maybe a frame along the edges or something might do the trick?
Would screwing a frame to the underside actually be strong enough to handle the weight, though?