# Building a stand: Place a board under or not?



## Jayse (Feb 15, 2012)

Well, I'm finally getting around to doing my build on my 112 gallon. I have the frame which was left from the previous stand that I will be using. I am getting ready to skin the frame out with 1/2" fir plywood.

My question is, should I place a sheet of plywood directly under the tank? What are the benefits to having a board under the tank versus not having one?? Also being that it is plywood, wouldn't it possibly crack under the weight of the tank sitting on top and just be a waste of time? The tank originally just sat on the bare 2x4's with the frame skinned around it.

I already have the wood, and have enough so that is not a factor.

Thanks for any advice


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## smitty814 (Sep 27, 2012)

Plywood under the tank would spread out the weight


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## ShortBus (Aug 17, 2005)

If its a typical glass tank, all the weight is distributed on the edges of the tank trim to the stand, you have different options from plywood to foam sheet to make the surface even and flat


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## Jayse (Feb 15, 2012)

Yes it is a typical standard aquarium with the trim on the bottom and top. So would there be any disadvantage to doing the plywood under other than extra work staining and sealing the wood?


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## smitty814 (Sep 27, 2012)

The plywood will help hold the framing together. Yes much more extra work. Ex. plywood edge looks terrible.


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## DanniGirl (Jan 25, 2007)

Unless the stand was designed with the need of a board, I wouldn't put it in there. It adds weight and unless it's marine grade plywood, chances are it will have voids within the sheet.


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## smitty814 (Sep 27, 2012)

I know that plywood of any grade will keep the top of your cabinet square. I would put it on the bottom as well. This is important so the structure doesn't rack with water and tank movement and collapse. Marine grade just means it's impervious to water not that it's a better grade. There are many grades of plywood that are plugged. Meaning no knot voids. It doesn't need to be 3/4" it could be 1/4" as it's job is to keep the framming square. So extra weight? Non issue.


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## lilscoots (Mar 13, 2012)

Like smitty814 said, the plywood would hold the framing together and square and doesn't need to be thick.


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## matt121966 (Mar 6, 2012)

board yes.


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## nodima (Oct 3, 2002)

It is not necessary, but would not hurt either. A possible downside is water getting between the tank and plywood and sitting there. I've never felt the need to use a plywood sheet under a glass tank. As long as your frame is reasonably well built the plywood skin on the ends and back is more than adequate to prevent racking.


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## DanniGirl (Jan 25, 2007)

nodima said:


> A possible downside is water getting between the tank and plywood and sitting there.


That's exactly why I would go with marine grade, the voids.

Unquestionably it would help with stability but if the stand is constructed to uphold the weight, then it's not necessary.

*Jayse*, are you going to skin the outside of the stand?


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## smitty814 (Sep 27, 2012)

If it's painted it doesn't matter what the top is made of. Paint keeps the water from penetrating. Sooooo because it may get wet is'nt a good enough reason to buy marine grade plywood. I personally don't have plywood on mine but wish I had. When I was moving it around while installing new flooring the stand developed a little wobble. Of course the tank was 3/4 full.


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## DanniGirl (Jan 25, 2007)

smitty814 said:


> If it's painted it doesn't matter what the top is made of. Paint keeps the water from penetrating. Sooooo because it may get wet is'nt a good enough reason to buy marine grade plywood. I personally don't have plywood on mine but wish I had. When I was moving it around while installing new flooring the stand developed a little wobble. Of course the tank was 3/4 full.


There are voids in construction grade plywood. Period.

My concern is the user could end up with unsightly voids after they rip the plywood to size.

Marine grade grade plywood must meet very *stringent naval criteria*. Period. 
Marine Grade plywood has a higher structural integrity than construction grade plywood.

ALL wood (EVEN marine grade plywood) must have a protective coating applied if it's exposed to water.

In this case, we're not looking at structural strength issue, I'm looking for a nice finished edge with no voids.

There really is no need to place plywood on the top of the stand. To put the plywood on the top will not stop racking. Racking is caused by lateral forces, not gravitational forces.* Smitty814* has a good idea to add plywood on the sides and especially the back to prohibit racking. Or, they could add an X brace to the back and sides.

*Smitty814*, was someone after you to move your stand? Was that why you moved it with a tank 3/4 full of water?


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## smitty814 (Sep 27, 2012)

DanniGirl you may know about fish......but leave construction to those that build.


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## nodima (Oct 3, 2002)

smitty814 said:


> If it's painted it doesn't matter what the top is made of. Paint keeps the water from penetrating. Sooooo because it may get wet is'nt a good enough reason to buy marine grade plywood. I personally don't have plywood on mine but wish I had. When I was moving it around while installing new flooring the stand developed a little wobble. Of course the tank was 3/4 full.


I've seen far more stands where hidden surfaces are raw wood than those where hidden surfaces are painted or otherwise treated. Face it, most people are lazy, and if something ain't gonna show, it ain't gonna get a finish. Most people would not even think of wasting time finishing plywood on top of a stand.

Frankly, your stand would have developed a wobble whether or not it had plywood on the top - the racking forces from moving the tank would not be mitigated by a plywood top.


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## smitty814 (Sep 27, 2012)

nodima said:


> smitty814 said:
> 
> 
> > If it's painted it doesn't matter what the top is made of. Paint keeps the water from penetrating. Sooooo because it may get wet is'nt a good enough reason to buy marine grade plywood. I personally don't have plywood on mine but wish I had. When I was moving it around while installing new flooring the stand developed a little wobble. Of course the tank was 3/4 full.
> ...


Yes I agree ppl are lazy. If you're going to take on what I would call a furniture build however, you should want to do it right and make it a piece of furniture. Not a shipping crate. As for my stand. Yes plywood would have kept it from racking.
Now back to the OP.
Plywood under the tank? Up to you. 
Benefits? Stated above.
Plywood cracking under the weight? Not a chance.
Waste of time? Again up to you.
Merry Christmas all......... :fish:


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## DrgRcr (Jun 23, 2009)

If you don't want to use plywood, you can accomplish stabilizing the tank without it. You can intall cross bracing or corner gussets to the framing in each direction to accomplish the same thing. I did the latter on a 125g over 75g 2x4 stand in my fish room. Very stable. If you do use plywood, you can hide the edges with iron on laminate edging. If you take your time and do it right, it will look like a finished edge. I did that on a 125 stand made exclusively with oak plywood and it worked very well. Here's the build thread from a few years ago.
viewtopic.php?t=197773


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## Jayse (Feb 15, 2012)

Thanks for all of the responses... I guess I should have explained the stand a little better. I'm the 3rd owner of this stand/ aquarium. Apparently for whatever reason I don't know, the original owner put some type of epoxy on the top of the frame in spots. My guess is to cover rough spots in the 2x4's. These spots can be seen in the 5th pic of my other thread here and are grey on the top of the frame:

viewtopic.php?f=4&t=242440

The aquarium had sat on these spots at my friends house for a few years with no issues. However, I didn't like the skin on the stand so I removed it, and I'm in the process of re-skinning it. I've already decided to add the top piece of plywood. The stand had only a piece of wood laying in the bottom section to hold the sump and pump. I've decided to also add playwood to that area as well.

Both the top piece that will lie under the aquarium will and the piece inside the stand will get stained as well as polyurethaning them and any joints.

Again, thanks for all the responses on here. Feel free to follow me build thread which I'm a bit behind on adding some pics to


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## Mschn99 (Dec 24, 2012)

i would not put any plywood under the tank. It will not distribute the weight out at all, because thats what the subflooring in your house is already designed to do. It will the the same load over the same number of square feet of subfloor either way. the second downfall (from first had experience) is if you have a moderate to major spill, you will get water under it, and its a pain at that point to get cleaned up. Its much easier to clean under a thin frame and get it dry than it is under a whole sheet of wood that you cant access at all. If your already putting a piece on top, that is plenty of support to keep it square and true.


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## Jayse (Feb 15, 2012)

Mschn99 said:


> i would not put any plywood under the tank. It will not distribute the weight out at all, because thats what the subflooring in your house is already designed to do. It will the the same load over the same number of square feet of subfloor either way. the second downfall (from first had experience) is if you have a moderate to major spill, you will get water under it, and its a pain at that point to get cleaned up. Its much easier to clean under a thin frame and get it dry than it is under a whole sheet of wood that you cant access at all. If your already putting a piece on top, that is plenty of support to keep it square and true.


 The plywood on the bottom inside is for a floor within the stand to hold the sump and pump along with other miscelaneuous equipment. It's not being placed underneath the whole stand itself or being used for any weight distribution.


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## Mschn99 (Dec 24, 2012)

Jayse said:


> Mschn99 said:
> 
> 
> > i would not put any plywood under the tank. It will not distribute the weight out at all, because thats what the subflooring in your house is already designed to do. It will the the same load over the same number of square feet of subfloor either way. the second downfall (from first had experience) is if you have a moderate to major spill, you will get water under it, and its a pain at that point to get cleaned up. Its much easier to clean under a thin frame and get it dry than it is under a whole sheet of wood that you cant access at all. If your already putting a piece on top, that is plenty of support to keep it square and true.
> ...


ever think about raising it up on some 2x2's so that if you ever had a spill you would have some airflow, and access for cleanup?


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## Jayse (Feb 15, 2012)

Mschn99 said:


> Jayse said:
> 
> 
> > Mschn99 said:
> ...


 It is raised. Look at the pics of the frame in the link within this thread.


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