DIY wooden stand for 96Lx30Wx24H -- What size lumber around the top frame if I only wanted one center support in the middle vs two

[brobak]

I'm planning out an unusually tall stand for an in-wall tank build from my garage through to my den. Given there is a 14" step up from the garage floor to the den, the stand will be over 50" tall, vs the more typical 36" stands.  I'm planning to go by the bog standard plans for DIY wooden stands you see in use all over the internet.

But given that I have a little more height than usual to work with, sI wouldn't mind losing a bit of it to the top frame if it meant I could have only one middle support leg vs the more traditional two required when you use 2x6's, if that is even safely possible.

 

I was wondering if anyone knew the right size lumber to use to make sure it wouldn't bow too much with just the one middle support. 2x8? 2x10? 2x12? More? Double up on any of those?

 

Would appreciate any insights. Thanks!

[cpeguero]

Shooting from the hip here - I had to reinforce the floor under my tank (similar size to yours, but a foot shorter). Had a structural engineer do the work. They just doubled up the 2x6 joists under the tank, on a 12-ish foot span. You might be able to just do something like that. Maybe  3 or 4 2x6’s running the length of the tank? If you want to be extra careful, run another support across the middle, between your two mid-span supports to support the center 2x6’s mid-span. 

[Origami]

Brobak, this is snapshot of a beam deflection calculator that I used in the past to design my in-wall tank setup over ten years ago. Its purpose was to validate the beam deflection and therefore beam size needed to meet my goal of having two posts (one at either end of the beam to maximize access underneath the tank. First, I want to point out that my beam construction actually uses a main beam plus a 2x4 oriented horizontally to stabilize the beam from horizontal warping. You'll see that in the drawing.  I'll also note that I addeda 3/4" plywood top, not shown. The legs in my (72") stand are constructed of two 2x4's arranged perpendicularly along their long edge and mounted to a 2x4 baseplate fastened to the concrete floor. The front of the stand is fastened into the wall studs to provide stability against racking. My 220 gallon tank sits 41 inches off the ground with this design using oversized 2x6's as the main beam. I've run the numbers for this design extended to your 96" - 300 gallon tank and it'll work with 2x6 beams, but I'd recommend that you go with the 2x8 for the added margin if you choose to go this route. Also, for safety's sake, given the long legs, I'd upgrade the top beam stabilizer, base plate, and legs to 2x6's. The calculation shows the beam deflection under the distributed load of the tank (estimated at 3600 pounds total) should be less than 1/20" using this design.

 

Hope this isn't too late and that it helps.

 

[brobak]

@Origami this is fantastic! Not too late at all, as I'm still several months away from water in the tank and finalizing the whole project. Just to be clear, are you plans calculated with no middle brace at all and just the open span?

 

I'm actually surprised that it'd work with 'just' 2x8's. Without the benefit of this calculator, I had just upped my plans to use 2x12's around the top, 2x6's on the legs, with one center brace in the front and two in the back, with a 2x4 base. I can trivially upgrade those plans to a 2x6 base, and I really like the idea that you have there where they are laying flat and are secured to the concrete floor vs vertically oriented, which will save me a few more inches in height.

 

Attached is what I had come up with without the benefit of this calculator.

[Origami]

Yes, just use 2x8 beams. No center post required. But note that there's an extra 1. 5 inches under the beams from the top stabilizer. This gives extra support for the vertical load, while providing some stability against warping (sort of like an i-beam).

Sent from my Note 10+5g using Tapatalk

[brobak]

@Oragami Yep, I see what you have going on there, and I can accommodate that easily in my plans.  Would you mind sharing the load calculator spreadsheet you have? No big deal if you dont want to, but I'd love to be able to run some different configs/calculations.

[Origami]

@Oragami Yep, I see what you have going on there, and I can accommodate that easily in my plans.  Would you mind sharing the load calculator spreadsheet you have? No big deal if you dont want to, but I'd love to be able to run some different configs/calculations.

Happy to do so. PM your email to me.

Sent from my Note 10+5g using Tapatalk

[brobak]

PM sent.

[AlanM]

This is a bit out of left field, but I'm a fan of making stands out of 3/4" plywood rather than 2x4 or other pre-sized lumber intended for framing.  Plywood is more dimensionally stable with less risk of a collapse from racking to the side if there's a sideways force applied to the top accidentally.  Yours looks like it will be very solid, but plywood does have the advantage of leaving lots of room in the stand for things if you need it.

 

Here were some build pics of the one I made for my 75g tank at the time showing how the pieces fit together.

 

 

[brobak]

I appreciate the nod towards the plywood, but I don't really have the tools that I would need to work with larger sheets like that. I do plan to tie the stand into the wall, and to put some 45 degree diagonal braces in to prevent racking and such on the back side where I don't need access.