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kc27 03-21-2010 07:04 PM

How Much of A Load Can A Floor Take?
I'm checking options of where to place a 55 gallon aquarium and solid oak stand and was looking for some advice. The total estimated weight of the filled aquarium and the stand is 700 to 725 pounds. The base of the stand where it comes in contact with the floor is 14" x 52".

I've read that aquariums of this size should be placed so that they are against a weight bearing wall, with the floor joists running perpendicular to the tank in order to spred out the load on more than one joist. Does that sound logical?

In my home, all the preferred spots for the tank would have the tank sitting parallel with the floor joists. Would having over 700 pounds of weight parallel to the floor joists damage my home?

Any ideas on this would be appreciated.

Daniel Holzman 03-21-2010 07:12 PM

This topic has been discussed repeatedly on this forum, check old postings. A heavy aquarium such as you describe is a point load, and a 700 lb point load is a lot. Consider that standard floor loading for a bedroom is approximately 40 pounds per square foot, so a single joist spaced 16 inches on center, 15 feet long, would only pick up approximately 750 lbs total, spaced over 15 feet. If that aquarium happened to be located over a single joist near the middle, there is a good chance you could cause failure of the joist.

Locating near a bearing wall is a good idea, and spreading over several joists is also a good idea. If this is not possible, you should retain a structural engineer to evaluate your specific situation. The fish might appreciate it.

Scuba_Dave 03-21-2010 07:26 PM

When we went looking for a new house I brought a tape measure & checked floor joists
I have a 125g that I wanted to install
At this house I ended up installing it over a main beam in the basement

I've had a 55g tank at both houses
At the last house I installed support in the crawl space to support the tank
At this house one end was over a support beam
It was against a wall that had 2 joists under the wall

The weight can cause a failure of the floor joists as Dan said
It may not habppen on Day one or even the 1st month
But it can happen or cuase the joists to sag
Then as they sag the tank goes out of level ...and can fail

Is there a basement below where you can add support ?
What size are the floor joists ?

kc27 03-21-2010 08:29 PM

Thanks guys. I wasn't being lazy, I started with a seach for floor, load, aquarium, and only came up with the guy who needed advice about a 360 gallon aquarium, which didn't seem to fully apply to my 55 gallon question.

Here are some additional details: the joists are are 2 x 8s, 16" apart. The span from a floor support beam to the exterior wall is 10 feet. The house was built in 1938. I do have an unfinished basement below, and could reinforce the floor from below with one of those adjustable posts that are sold at the home centers. Or I could just leave the tank in the basement.

Here is a crude diagram of what I've got. Thanks again for your help

Scuba_Dave 03-21-2010 09:13 PM

Basement is best w/solid concrete
If you want to move it upstairs then you need to re-inforce/support the floor
I'd sister another joist along the one the tank will be on all the way to the support beam
Possibly even the ones one either side too
Then at the other end of the tank install another support beam spanning at least 3 joists
Tie the joist the tank will sit on into the ones on either side with blocking

kc27 03-21-2010 09:27 PM

Thanks for the response ScubaDave. After thinking more about it, adding a post for the additional support beam is going to be a real obstacle in the basement.

It seems my options are to either change the aquarium placement so it is against the wall that is above the support beam or against the exterior wall. Or maybe leave it in the basement where their are no support worries with the concrete floor.

I guess on the bright side I'm considering the load on the floor before moving the tank, rather than after, when damage would have been done. Thanks again for the advice.

Scuba_Dave 03-21-2010 09:44 PM

I built my 125g basically "in wall"
But I opened the wall it sits on the wall & on a 1/2 stand I built into the wall
Each corner & the middle are 4x4 posts, then 2x's between them
All sitting on a 2x6 that spreads out the weight
You never want a tank to leak

4just1don 03-22-2010 07:42 AM

dont buy such 'heavy fish,lol. If you get that much weight out of that tank,,the tank weghs more than I think it does. 8# a gallon is 440# for 55 gal. which you prob neverfill to the very rim.

more like 400 I am guessing plus maybe 50 pounds for tank and base. think your weight is one of those 'shipping weight' values

kc27 03-22-2010 10:08 AM

For anyone else considering a similar question, I did find this article, written by a structural engineer, titled "Residential Wood Framed Floors and Aquarium Weights". The article goes into a lot of detail about the load that an aquarium can put on a floor

Scuba_Dave - your tank installation looks like a well thought out plan. I took another look at the area in question of my floor, just to revisit the idea of sistering the joists. It would be more trouble than I care to go through - electrical and phone cables are attached to, and in some cases go through the joists..

4just1don - I got the aquarium weight from this chart

HooKooDooKu 03-22-2010 12:16 PM


Originally Posted by 4just1don (Post 417907)
8# a gallon is 440# for 55 gal. which you prob neverfill to the very rim. more like 400 I am guessing plus maybe 50 pounds for tank and base. think your weight is one of those 'shipping weight' values

A rough ESTIMATION of the weight of a fish tank is 10# per gallon. Water is only part of the equation. First of all, there is the weight of the glass. Then, water isn't the only thing in the tank. There is usually rock or sand which is much more dense than water.

In this case, kc27 also made mention of a stand. That can add to the weight by a few pounds for a light weight metal stand to 100# or more for a fully custom built cabinate.

Then you have to add things like pumps, filters, lights, etc.

So 700# for a 55 gallon fish tank is quite reasonable to expect.

stuart45 03-22-2010 12:32 PM

I've got a 45 gal cold water storage tank in the loft which is spread across 4 ceiling joists by 4x2 bearers on a plywood base. This is normal for Building Regs, although for smaller tanks 3 joists is enough.

Scuba_Dave 03-22-2010 12:49 PM

The tank alone weighs about 80 lbs, stand could be another 50 lbs
50g of water x 8.34 = 417 lbs
Many aquariums also have a hood & lights in the hood
Pumps, air pumps, filter, cleaning equipment, fish food etc
Then of course items will be stored in the stand

In addition you need to figure additional weight of a few people standing around looking at the tank
I've had as many as 8 people looking at my tank at once, that can be over 1000 lbs right there
That load will normally be taken up by the surrounding floor

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