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I am planning on building some furniture which has to support 2 aquariums. I have found many examples online of a simple design which uses 2x4s constructional softwood to build a box for the aquarium to sit on.

I am wondering if I picked a hardwood to build it, if I would be able to use smaller dimensions of the wood for the same strength?

For example, if I used maple could I achieve the same strength using 1x3s?

Update

The aquariums are going to be 300 litre 120cm x 50cm x 50cm (48" x 20" x 20"). So lets round up and say a live weight of 400kg per tank.

I was thinking of using this design:

https://www.aquariacentral.com/forums/data/attachments/129/129127-077d722003f604ee5ee3f8dc284d5061.jpg

https://youtu.be/jN4Y9AYuwcQ?t=980

The key parts are:

  • Going to put ply on the back and the top
  • Weight is supported by the timbers not the screws
  • 8 legs in total (two in each corner)
mmathis
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Andy Flatt
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    Andy can you provide some more details on the tank you are planning to put on top of the stand you are making? Knowing how much weight it needs to support is important to know in answering this question. – James Oct 22 '18 at 14:58
  • Some refs: http://workshopcompanion.com/KnowHow/Design/Nature_of_Wood/3_Wood_Strength/3_Wood_Strength.htm, https://www.engineersedge.com/lumber.htm –  Oct 22 '18 at 15:02
  • The basic answer is most definitely a yes, as you can see easily by comparing the form of typical softwood tables with hardwood ones which typically have much skinnier legs and often a thinner top too. But for holding significant weight there's so much more to it than just the inherent stiffness of the wood species used, There are numerous ways to impart strength while slimming down on the structural members, not limited to 1) by incorporating one or more panels of MDF or ply, which greatly add to stiffness if used right, 2) by adding diagonal braces 3) choosing the strongest joints. – Graphus Oct 22 '18 at 18:40

3 Answers3

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It depends.

Hardwood and softwood are not terms describing the strength of the timber - they describe whether the trees are conifers or broad-leaf trees. Different timbers have different strengths and in general, hardwoods tend to be harder than softwoods ... but as I say "it depends". Both ebony and balsa are hardwoods, and their structural properties are ... not identical.

Having said that, for most timber the difference in strength and stiffness is not that great. I would not expect to be able to go from a cross-section of 8 square inches to 3 square inches - more like 4x2 to 3x2.

Martin Bonner supports Monica
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There are tools on the internet such as the sagulator (click on the 'design' tag and select more info to find a link to the sagulator) that can assist you in determining if a piece of wood can support the weight of an aquarium. In all likelihood the corner posts will easily hold the weight, but the horizontal spans will be much more questionable. You will need to consider the species of wood being used, the length of span, and the depth of the beams (the beam width should not be less than 3/4"). Remember that water weighs 8.4 pounds per gallon. To that you must add the weight of the aquarium and any rocks or other decorative items added to the tank environment.

Beyond weight bearing, the most critical consideration is with the connections. Heavy loads will have a tendency to twist the individual beams and posts that may also affect the entire frame assembly. The connections between members must be able to transfer the weight and resist any lateral loads that occur in the assembly. One way to resist these loads is to include firmly secured plywood panels at the sides, top and near the bottom of the frame. I do not recommend screwed connection but instead use traditional woodworking connections including mortise and tenon connection and plenty of water resistant wood glue.

Ashlar
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Weight is supported by the timbers not the screws

The tank will crack, because the support is in the four corners.

You need to support the entire perimeter of the tank's base. Water tanks sit on small edges with the floor of the tank unsupported. In the video reference example, the tank would have to sit with the footprint near the edge of the table to ensure safely.

The tank should be on a flat surface that is level and will not deform under the weight of the tank. So the surface itself needs to be evenly supported.

The stand should be able to resist a tanks weight from a lateral force. So you need the stand to support 400kg of force from the side. Picture a small child running upto the tank and slamming into it with their hands.

If you are in doubt about how to build a tank stand, then I advise you to purchase one from a pet store that is rated for your tank. You are describing a large tank and the forces there are huge.

Reactgular
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