Will this floor support a 55+?

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Aquarium Advice Freak
Mar 22, 2006
Redding, CT
I'm thinking of putting a good size tank in my bedroom, which is on the 2nd floor of our house. Its an old house which is constructed as a balloon frame.

I'm thinking about putting a 55-75gal in there. The floor joists are 2x6's @ 16" on center. The flooring in here (there's no subfloor, just boards on top) is 2" thick and 8" wide, pine.

This all seems to me like it would hold, but since its a balloon frame I'm not really sure. My dad says its fine with him that I put a large tank upstairs providing that I'm sure the floor wont collapse.

Can anyone provide some insight?

yea i wouldn't go 75, but stick with the 55 max.
sounds solid enough, I just wouldn't want the risk
I had my 55 on a top floor apartment. You could literally see the point where the floor dipped off from the level of the main room (it was kinda off in an alcove) and it creaked when you walked past. Every day I prayed it wouldn't go through the floor. We made it though :)
I doubt you'd have those problems. I bet your house is better contructed than our apartment. Wood can compensate for weight, in that it should give some warning if it won't hold - the floor or ceiling would bow. It won't just snap without warning. It just may not be much of a warning, heh. Just make sure there are no beds or whatever under it, to be safe, but yeah, you sound ok.
Are their any sites online where I could find a reference to its strength?

I doubt he'd have a problem with putting a 55 in, but I think he'd want better evidence than "these guys on this fish forum said it would be fine!"

But its looking good sofar. I think as long as I put it across the joists and maybe throw a 1/2" slab of plywood down then I should have nothing at all to worry about.

Thanks guys.
your gonna wanna keep in mind the age of your house, the older the floor joists, the worse off your gonna be, most modern day lumber is set to a standard of something like 1000lbs per square foot, don't quote me on the exact number though
I would contact the local building inspector. They should be able to come out and tell you if you can safely support even a 55.
fish_4_all said:
I would contact the local building inspector. They should be able to come out and tell you if you can safely support even a 55.

My advice as well. It may cost you some money but it will put both you and your parents at ease. 55g is a lot of weight, especially in an old house.

Houses in my area I wouldn't go over a 55g, even then I'd be a bit worried. Most are 100+ years old.
you could also use something like a load spreader, build a stand and make it wider than the tank and longer and that will help spread some of the weight over a greater distance than just the 48 x 12 rectangle footprint.
Thebluyak said:
you could also use something like a load spreader, build a stand and make it wider than the tank and longer and that will help spread some of the weight over a greater distance than just the 48 x 12 rectangle footprint.

I could do that. I plan on building my own stand anyways, so it wouldnt be hard to make it 2' longer or so.

Another thing I forgot to mention was that the floorboards in here arent done like a typical hardwood floor where you have many pieces of wood, the floorboards in here run the entire length of the room. So one board runs from the door to the opposite wall, which I'm sure would be great for added strength.
You would do best to locate the tank near a load-bearing wall and perpendicular to the floor joists.

Outside walls would be load-bearing.

you could try to set your tank like this to the joists (the dashes are joists and the Ts are the bulk of the tank). This will spread the load of the tank across multiple joists and have it as close to the load bearing wall as possible. Most houses can support a waterbed, so a 55G should not be a problem.

The houses are strong, otherwise the construction wouldn't be the basis for almost all housing today. The only real concern should be whether the floor joists sit on top of the walls or not. Some older houses don't, I know, I am living in one and the floor upstairs are not on top of the wall and therefore pulled away from the walls with standard bedroom weight. I can understand not wanting to call an inspector if dad might say no.

If you can see for certain that the floor joists are on the walls to the outside then there shouldn't be much worry at all. If in the middle of the room and of an exterior wall then you could be fine if there is a supporting wall under the wall you are putting it against.

This being said, I would still at least consult an engineer or the inspector to make sure you aren't setting up for a huge crash. 750+ pounds is a LOT of weight!
Older houses (depends how old) probably have stronger floors as they used lumber which wasn't planed so a 2 x 4 was actually 2" x 4" instead of 1 1/2" x 3 1/2". I'm not sure when they started planing the 1/2" off lumber. Probably in the 70's or 80's.

If the house is really old, and if it gets cold where you live, you might want to avoid placing your tank by an exterior wall, as older house may lack insulation.
Im an Architect and Ill do the best to give some rational to the discussion. There have been some good points made so far, but some people are missing the fact that this is a ballon framing system.

Ballon framing is a system in which the walls carry the floor load at levels 2 and above. The floors are "hung" on the wall, similar to how most people build decks. This type of construction is satisfactory as far as distributing uniform loads, however not good for point loads, or isolated conditions like in this instance, an aquarium.

The fact that you have 2" pine floor boards on top of rather small joists does help in the situation as it helps to carry some of the load to adjacent joists even if the aquarium isn't sitting on top of them. Most new construction of 5/8" or 3/4" plywood subflooring wouldn't have this kind of ability.

I do agree that your best bet is to position the aquarium so that it is crossing as many floor joists as possible. Older houses typically use actual size members so a 2x6 is truely 2 inches by 6 inches, however in my eyes, this still seems pretty small. Depending on the span of the room or the length the joists are running will be important in this equation. A shorter span means that the deflection (or how much the floor joists bend) are less, which in turn means the opposing bearing wall of the structure will begin to pick up so of the load, as well as the bearing wall you have the aquarium backed up to. I can't see the span being very long due to the size of your joists.

One concern I do have is the fact that this home may have been constructed to utilize this "upstairs" space as an attic area. Attics conversions typically arn't "beefed" up to the standard capacity as a designed floor would be. If this is the case, I would take great care. For instance, a typical uniform load for an attic is somewhere around 15 pounds per sq. ft. (depending on local building codes) where a second floor design would incorporate around 40 pounds per sq. ft.

If in fact you are living in an attic conversion, there are things you can do, however not much beyond yanking up your floor boards and providing "sistered" 2X6s on the existing to help in picking up the load, and reducing deflection. One other thing you may need to do is to beef up the connection to the wall. If the house is ballon framed, the capacity on the connections may need a little help.

If you have anymore questions, please let me know. As always, with out an inspection of the property and the construction type, as well as lack of calculations, this information is not guaranteed, and I cant be held liable for any subsequent concequences
That article is good with the exception that the Author pretty much only talks about one type of framing method.. platform. Most new construction is that way. The original poster is dealing in the type of construction as balloon framing:


which will have additional concerns above and beyond what that author talked about. You are right though, very good and informative article
Interesting read. What does a full 55 weigh with everything? 450-500lbs tops? That is realistically two big guys standing next to each other. I've had 55's in a couple of different rooms in my house and I've never noticed even the slightest sag in the floor. My buddy put his 125's all over his older home and agian we couldn't see any signs of saging and we had 2 125's withing 5 feet of each other. But then again these houses wasn't built like the one in question. Best of luck.
Actually probably closer to 700 lbs. This doesn't include the weight of the stand, the filters, the glass top, and the lighting. Ths also assumes 1.5 inches of substrate, not 2-3 inches. So it could be around 750-800. Add a sump and you add 100-200 pounds. Final weight of everything could be in excess of 1000 lbs.
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