# Calling all woodworkers: questions about framing to support 300lb fish tank **URL:** \ **Category:** In My Humble Opinion\ **Created:** [April 21, 2012, 3:09pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502 "2012-04-21T15:09:14Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [April 22, 2012, 3:36pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/21 "2012-04-22T15:36:49Z")
> [@John\_Mace](#): > > Yep, but door and window headers usually use 4x material, I thought they were 2-2 x 4 with a piece of 1/2 " plywood in between. šŸ˜• ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 22, 2012, 3:39pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/22 "2012-04-22T15:39:54Z")
> [@carnivorousplant](#): > > I thought they were 2-2 x 4 with a piece of 1/2 " plywood in between. šŸ˜• You can do it that way, but itā€™s more work. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 22, 2012, 3:52pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/23 "2012-04-22T15:52:51Z")
> [@carnivorousplant](#): > > I thought they were 2-2 x 4 with a piece of 1/2 " plywood in between. šŸ˜• Itā€™s common to do that with any 1/2" material in the center. Itā€™s matching the depth of a doubled 2x4 (3") to the width of a 2x4 side (3 1/2"). For a lintel or header, itā€™s the vertical 3 1/2" that counts most for strength, not the horizontal depth. Using two 2x4s is often easier than using a 4x4 because you canā€™t cut the 4x4 wood with a single cut on a common circular saw, and often no 4x4s are available while thereā€™s always an excess of 2x4 lumber. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 22, 2012, 4:01pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/24 "2012-04-22T16:01:57Z")
> [@TriPolar](#): > > Itā€™s common to do that with any 1/2" material in the center. Itā€™s matching the depth of a doubled 2x4 (3") to the width of a 2x4 side (3 1/2"). For a lintel or header, itā€™s the vertical 3 1/2" that counts most for strength, not the horizontal depth. Using two 2x4s is often easier than using a 4x4 because you canā€™t cut the 4x4 wood with a single cut on a common circular saw, and often no 4x4s are available while thereā€™s always an excess of 2x4 lumber. I see a lot of new construction, and Structural Plans always call for 4x headers. On a professional job, you plan in advance what material you need for things like headers, so that isnā€™t a problem. DIY, and all bets are off. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [April 22, 2012, 4:30pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/25 "2012-04-22T16:30:19Z")
> [@John\_Mace](#): > > You can do it that way, but itā€™s more work. Seen it both ways. Depends on whatā€™s on hand. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 22, 2012, 4:35pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/26 "2012-04-22T16:35:42Z")
> [@John\_Mace](#): > > I see a lot of new construction, and Structural Plans always call for 4x headers. On a professional job, you plan in advance what material you need for things like headers, so that isnā€™t a problem. DIY, and all bets are off. Sure if itā€™s in the materials list theyā€™ll have the 4x4 material. But Iā€™ve seen specifications for headers that only provide the depth of the header, as 2x4, 2x6, 2x8, etc., and the builder is expected to know how to construct a header. CA has some strict building codes and possibly using 4x4 is required there. Since weā€™re having the OP rebuild his entire house now, Iā€™d suggest checking the joist size on the floor under the fish tank. Besides reframing his windows he might have to rebuild the floor also šŸ™‚ Back to just the fish tank, I donā€™t think the wall strap is useful unless you have a weak or unstable stand to start with. Fish tanks are heavy, and would be very difficult to tip over. A sturdy stand is the best way to ensure safety. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 22, 2012, 6:31pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/27 "2012-04-22T18:31:52Z")
> [@TriPolar](#): > > Sure if itā€™s in the materials list theyā€™ll have the 4x4 material. But Iā€™ve seen specifications for headers that only provide the depth of the header, as 2x4, 2x6, 2x8, etc., and the builder is expected to know how to construct a header. CA has some strict building codes and possibly using 4x4 is required there. I think everyone in the US is on the UBC now, just like CA. ---
**Author:** ![simster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/simster/32/1047_2.png) [@simster](https://boards.straightdope.com/u/simster)\ **Post date:** [April 22, 2012, 8:26pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/28 "2012-04-22T20:26:34Z")
> [@TriPolar](#): > > Sure if itā€™s in the materials list theyā€™ll have the 4x4 material. But Iā€™ve seen specifications for headers that only provide the depth of the header, as 2x4, 2x6, 2x8, etc., and the builder is expected to know how to construct a header. CA has some strict building codes and possibly using 4x4 is required there. > > Since weā€™re having the OP rebuild his entire house now, Iā€™d suggest checking the joist size on the floor under the fish tank. Besides reframing his windows he might have to rebuild the floor also šŸ™‚ > > Back to just the fish tank, I donā€™t think the wall strap is useful unless you have a weak or unstable stand to start with. Fish tanks are heavy, and would be very difficult to tip over. A sturdy stand is the best way to ensure safety. If weā€™re going to talk floor joists - I would set the tank in the room so that it runs perpindicular and accross as many as possible - and if you have to have it running parallel - plan your stand to be atleast 18" deep to account. While a 300 pound tank is ā€˜not muchā€™ - if you donā€™t set it correctly, you may end up causing a weak floor structure by splintering/splitting the underlayment. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [April 22, 2012, 10:31pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/29 "2012-04-22T22:31:36Z")
> [@beowulff](#): > > A single 2x2 can easily support 300 lbs of vertical load. You will have 4 of them. > The issue is ā€œrackingā€ or shear force - you need to brace the box diagonally, or use a plywood skin to remove any possibility that a side will change from a rectangle into a parallelogram. When your stand is done, you should be able to brace the bottom edge and push with all your strength on the opposite top edge, and not move the sides out of true. If so, your stand will support the tank with no issues (although tying it to the wall isnā€™t a bad idea, as mentioned above). From my structural engineering days, thatā€™s basically correct. A structure can fail in several ways: Compression - In the case of the OPā€™s fish tank frame, the weight of the tank would crush the vertical 2x2 columns, causing them to splinter. This is unlikely as the compression strength of a 2x2 of wood is well over 1000 lbs. Buckling or torsion - While the cross section of your 2x2 can handle the compressive force, that is assuming an axial load directly applied along the center of gravity. In reality, slight imperfections and uneven load distributions actually result in a somewhat ā€œeccentricā€ loading. In laymens terms, the longer your vertical columns, the more likely it might buckle or twist (torsion) under the same weight. IOW 6" long 2x2s will support a 300lb fish tank but 10 foot long 2x2s wonā€™t. Not without some sort of cross bracing. Shear failure - Unlike a buckling or torsion failure, your individual columns will remain intact. But a slight push to the side will collapse the whole thing like a house of cards. It doesnā€™t matter how think your columns are because the failure is in the joints. My advice if you want to make a solid fish tank frame: Take 2 38" x 14" pieces of plywood. (2" wider than the base dimensions of your tank). Make a box using the plywood sheets as the base, top and 4 2x4 s the desired height. Use appropriately sized nails and wood glue for each connection. The long side of the 2x4s should be parallel with the long side of the tank Cover the back and sides with sheets of plywood, glueing and nailing all along the edges. Nail a 1"x1" edge around the top that the tank will fit into. That should be pretty solid. 2x2s would probably do the trick, but why take chances for a few bucks? Also, a 2x4 gives you more space to use heavier nails. [This PDF is helpfull if you want to get all ā€œscientificā€.](http://www.awc.org/pdf/WSDD/wsdd.pdf) ---
**Author:** ![xanthous](https://avatars.discourse-cdn.com/v4/letter/x/53a042/32.png) [@xanthous](https://boards.straightdope.com/u/xanthous)\ **Post date:** [April 23, 2012, 1:15am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/30 "2012-04-23T01:15:01Z")
I live in a ground-floor apartment with no basement. So I guess the floor is likely cement under the carpet? ---
**Author:** ![xanthous](https://avatars.discourse-cdn.com/v4/letter/x/53a042/32.png) [@xanthous](https://boards.straightdope.com/u/xanthous)\ **Post date:** [April 23, 2012, 1:19am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/31 "2012-04-23T01:19:32Z")
Oh, and also- this stand is being built in my boyfriendā€™s basement, and will have to be transported here, and itā€™ll also move with me one day when I move, so if itā€™s structurally possible that it can be built safely/sturdily with 2x2s, then i suppose itā€™ll be that much less difficult to transport. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [April 23, 2012, 1:36am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/32 "2012-04-23T01:36:02Z")
The commercial ones I have assembled are made of 3/4" plywood or particle board, and Iā€™d hate to move one. The racking strength would be shot to hell, that is, they would become wobbly after being push and shoved around. If it is to be moved, Iā€™d go for 2x4s and screws. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 23, 2012, 1:37am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/33 "2012-04-23T01:37:50Z")
To give you an idea of how strong wood is, [here](http://www.youtube.com/watch?v=OmLnxIKHJYY) is a video of a ā€œtoothpick bridgeā€ contest, where a bridge made only out of toothpicks and glue, and weighing no more than 100 grams ends up supporting 3,000x itā€™s weight (!). ---
**Author:** ![simster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/simster/32/1047_2.png) [@simster](https://boards.straightdope.com/u/simster)\ **Post date:** [April 23, 2012, 1:45am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/34 "2012-04-23T01:45:47Z")
> [@xanthous](#): > > I live in a ground-floor apartment with no basement. So I guess the floor is likely cement under the carpet? Depends on if it is built on a slab or if it has a crawlspace. ---
**Author:** ![appleciders](https://avatars.discourse-cdn.com/v4/letter/a/85f322/32.png) [@appleciders](https://boards.straightdope.com/u/appleciders)\ **Post date:** [April 23, 2012, 1:53am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/35 "2012-04-23T01:53:12Z")
> [@xanthous](#): > > I live in a ground-floor apartment with no basement. So I guess the floor is likely cement under the carpet? Maybe. Thereā€™s almost certainly a cement foundation, but there may be another layer between you and the foundation to accommodate electrical conduits or plumbing. Itā€™s hard to say. ---
**Author:** ![xanthous](https://avatars.discourse-cdn.com/v4/letter/x/53a042/32.png) [@xanthous](https://boards.straightdope.com/u/xanthous)\ **Post date:** [April 23, 2012, 10:47am UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/36 "2012-04-23T10:47:37Z")
> [@carnivorousplant](#): > > The racking strength would be shot to hell, that is, they would become wobbly after being push and shoved around. > If it is to be moved, Iā€™d go for 2x4s and screws. hmmm, I donā€™t like the sound of this. My BF lives an hour from here, and intends to transport this in the back of his truck. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 23, 2012, 1:22pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/37 "2012-04-23T13:22:23Z")
Well, you can listen to the people who are telling you what you want to hear and build it out of 2x2s, or you can listen to the people who know what their talking about and build it out of 2x4s. 2x2s spanning 3 ft and at a counter height of 3 ft will be wobbly as hell unless you brace the shit out of it. In which case you might as well build it out of 2x4s to begin with. And definitely use screws, not nails. You can do something fancy like taper the 2x4s at the bottom so they donā€™t look so bulky or just drape the whole thing in fabric to hide the structure (the easy thing to do). Framing lumber, Doug Fir, is not very attractive anyway. ---
**Author:** ![xanthous](https://avatars.discourse-cdn.com/v4/letter/x/53a042/32.png) [@xanthous](https://boards.straightdope.com/u/xanthous)\ **Post date:** [April 23, 2012, 2:55pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/38 "2012-04-23T14:55:09Z")
> [@John\_Mace](#): > > Well, you can listen to the people who are telling you what you want to hear and build it out of 2x2s, or you can listen to the people who know what their talking about and build it out of 2x4s. 2x2s spanning 3 ft and at a counter height of 3 ft will be wobbly as hell unless you brace the shit out of it. In which case you might as well build it out of 2x4s to begin with. And definitely use screws, not nails. > > You can do something fancy like taper the 2x4s at the bottom so they donā€™t look so bulky or just drape the whole thing in fabric to hide the structure (the easy thing to do). Framing lumber, Doug Fir, is not very attractive anyway. The plan is definitely to skin it with a decent quality, stain-able 3/4" plywood, so whatever frame there is would be anchored by the skin (and screws, not nails). According to my woodworking boyfriend (yā€™all are my second opinion šŸ˜‰ ), a 2 x 2 frame with 3/4" plywood is way more support than the store stands provide. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [April 23, 2012, 3:53pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/39 "2012-04-23T15:53:34Z")
Weight wise (probably cost wise too) I think you would be better off with 2 by 4 s. Use 1/4 or perhaps 3/8 inch plywood for the sides and back. Use good long screws, along with good quality wood glue where any wood surfaces come together and that sucker will be plenty rigid IMO. Give the wood glue as much time to dry as you can stand before you load it up with the tank. ---
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [April 23, 2012, 5:03pm UTC](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502/40 "2012-04-23T17:03:05Z")
> [@xanthous](#): > > The plan is definitely to skin it with a decent quality, stain-able 3/4" plywood, so whatever frame there is would be anchored by the skin (and screws, not nails). According to my woodworking boyfriend (yā€™all are my second opinion šŸ˜‰ ), a 2 x 2 frame with 3/4" plywood is way more support than the store stands provide. Now I am confused. If you are definitely to skin it with decent stain-able plywood then why not consider Shop steel metal shelving at Loweā€™s? There are good explanations, perhaps no Loweā€™s with reasonable distance. The question is part rhetorical and part inquiry. [Previous page](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502.md?page=1) [Next page](https://boards.straightdope.com/t/calling-all-woodworkers-questions-about-framing-to-support-300lb-fish-tank/619502.md?page=3)