Will this shelving design safely hold 2100lbs?

Question

I would like to add some built-in shelves to a room in my house. It will hold several aquariums, so they need to be quite strong.

I’ve sketched out a plan (see below), but I’ve never built anything like this before and I’m wondering if this will work.

The shelves will be about 72 inches long, 22 inches deep, and there will be three of them.

Each shelf will need to support about 700 pounds, evenly distributed.

My idea is to support the back edge with a cleat attached to the four studs with GRK structural screws. The front of the shelves will be attached to 4x4 posts.

My plan for the shelves is to make them out of three-quarter inch plywood supported in the front by an LVL 2x4 spanning between the two 4x4s. The plywood will be screwed into the LVL 2 x 4 and the cleat. The plywood span between the front and back will be supported by 2x4 braces on on each end and every 16” on centers, screwed into the LVL and the back cleat.

I was going to cut dados in the 4x4s to support the LVL 2x4 and the plywood, and use structural screws to attach the LVL to the 4x4s.

I’m planning to use the LVL 2x4 to accommodate the long span. I realize that a center post would make this all easier, but for aesthetic and usability reasons, I really would like to avoid a center post.

The wall and the 4x4 posts both rest on the slab foundation.

Answer 1

The 2x4 rails will not be adequate. The walls of the aquarium are very strong in shear, but guidelines suggest full support anyway. This won't give you that. For a 72" span I'd want single or even doubled 2x6--something with a taller section.

Then, unless your aquariums are also 22" deep you need support under the plywood at the aquarium permiter. Don't rely on the plywood to span much at all.

Also, keep in mind the critical nature of diagonal bracing. If you use wall cleats you're covered. If not, you need something robust to prevent a flop. X-bracing of some sort or a back panel would do if well anchored.

Otherwise I think you're ok. Do consider a simple stack of concrete blocks with layered shelves, though. A pair of 4x6s (on edge) with no plywood would work well, even without plywood.

See also my answer to a similar question.