In my utility room where I am placing my 50 gallon electric hot water heater, I have tall ceilings (10 feet), so I am trying to be space efficient and put my hot water heater as close to the ceiling as possible (accounting for piping, etc) and then making some use of the space below (like a cabinet or shelving). I should also note that my water heater is a short, wide model. So I am thinking that the stand I am building needs to be able to hold 500 lbs of weight. I was thinking that 2x4s for the legs (with 1/2" plywood for bracing/racking) and a top on which the water heater sits made out of thick plywood (at least 3/4").
Thoughts?
How tall do you plan on making your platform? Personally, I would probably err on the side if "stout" and use 4x4s for the legs and also attach the platform legs firmly to the adjacent wall studs if possible (lag bolts or metal strapping on both platform and tank to provide seismic bracing if area is prone to shakers). The 1/2" plywood should suffice for the racking braces and I would certainly use 3/4" minimum for platform.
You may also want to consider some sort of waterproof protection. Like if the tank leaks, a place other than your "below" storage or the floor for the water to go. Some water heaters sit in a sort of tray that has a runoff "spout" to direct errant fluids away from things you care about.
You can buy water tank trays at any big box home improvement store.
Ours is elevated about 18 - 20 inches. They built the framework out of 2x4's with 16" centers, 3/4" sub flooring on that.
I am hoping to make my stand tall enough that I can put a cabinet underneath...so at least 36", perhaps 48". I like the idea of affixing the stand to the concrete walls in addition to the earthquake straps. It is going in a corner with two concrete walls.
You could easily construct site built corbels or angled brackets out of 3/4" plywood , set a shelf on it, well attached with screws., Still strap your tank to the walls in the corners.
So your floor space could be free for other uses.