2x4 strength/spans etc

[Cory]

So I'm hoping either someone already knows where the article on this exists on the internet or can chime in with real life experience with aquarium racks.

basically I'm wanting to know how long of a span a 2x4 or 4x4 could hold 20g fish tanks. I'm thinking about makin ga modular setup in my fish room that allows me to change it if i want using 2x4 or 4x4 and cinder blocks.

The trick being that more supports aka cinder blocks ties up 8 more inches of rack space. So I'm wondering if I can get a 10 foot 2x4 and have it vertical with a sheet of plywood over it. support 4 20g tanks. With the 2x4s only being support at the ends making like an 8 ft span.

 

[Bob]

Couldnt you build it like Jay and Carols fish room?

 

[Cory]

Sure, I can build it any way really. I'm mostly doing concrete because I haven't done it yet. Short of welding up aluminum stands, I've worked with every other type of stand out there. All have their pros and cons. For instance, a wood stand can rot when wet etc. In fish farms a lot of times it's concrete so you can water change straight onto the floor and have it sloped to the floor drain.

Also it's another youtube video, how you can basically build a rack of fish tanks in about 20 minutes. I've been in contact with some big breeders who do it this way. I'm not longer worried.

 

[Cory]

Also I don't like wood racks in the center of rooms cause you have to anchor to ceiling/floor and it's not as strong compared to anchoring to a wall.

 

[hose91]

You would have a front and a back 2x4 supported on each end? I think with 20G tanks you'd probably be ok. Wood in compression is much, much stronger than wood in deflection, so at the midpoint you could use something as small as a 2x2 for a vertical support and it would alleviate any deflection issues. Alternatively, you could use a 2x6 on end instead. The stiffness in a rectangular beam is roughly proportional to the cube of the height of the beam. Going from a 2x4 to a 2x6 then requires nearly four times the force (weight) to create equal displacement at the center of the beam (the 5' mark).

So, you might be ok with a 10' 2x4 span and small tanks, but to be sure i'd put a small wood brace in the center, or I'd increase the thickness of the beam you're using.

 

[Cory]

Thanks. I think im gonna use 4x4s and put a block in the center also. Mostly because a 2x4 could roll and id have to build a platform out of it. A 4x4 should be stable.

 

[justin case]

Don't use 4x4s for any horizontal application. They are posts. Meant to be vertical. Go with 2x4 but use 3 with one in the middle and you will be fine. Or you could make a T using one 2x4 nailed in the center of another 2x4. But in general any board that is square isn't suitable for horizontal framing.