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Question DetailsAsked on 1/6/2017

1930 house second floor, will it hold a 2500 lb fish tank spanning across 7 beams 28 square foot area not flat fl

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I once researched 1930's building design codes for a complete building reconstruction job - NYC the code in much of the 30's called for 15 psf - 15 pounds per square foot - residential loads, though I have since seen actual design documents for a brownstone row house from the end of the 1920's that showed 10 psf design live load (in addition to the building materials dead load) for top-floor bedrooms. Modern design loads are generally around 30 psf for bedrooms and 40 psf for other rooms in residences. And bear in mind back then 30" and even 36" joist spacing was not uncommon with 2-4 inch thick solid plank flooring - so unless you have actually seen them, do not count on 24" joist spacing. Ditto in walls - back then many were built at 24" stud spacing or even with 2x2 or 2x3 studs on interior walls, so counting on the joist supporting walls to carry the load might be hopeful wishing also. In fact, some interior non-load bearing or bedroom floor-only bearing walls before about the late 1940's were actually 1x3 or 1x4 material set sideways as "studs" - not so much for strength as just to provide something to apply the lath and plaster to, so the "wall" those floor joists sit on might actually just be a plaster shell, not a structural load-bearing wall at all. Something to check out.

You are talking around 90 psf ! Far above and beyond any residential loading. While the floor joists MIGHT take the load IF the room does not have other substantial loading, if the tank was along a real load-bearing (at next floor down) wall oriented particular to the floor beams, and IF you never have parties with lots of people in that room ... And remember, this would not actually be a "live" load like people - it would be a long-term dead load, so deflection of the beams comes into play, because you do not want massive sagging could be several inches easily) even if the beams can safely carry the weight. And of course, the condition of the joists and the josit connections at beams or walls wouldneed to be confirmed.

I have seen cases where even relatively modern homes had floor failures due to water beds - at about 40-60 psf floor load and similar or a bit less total weight than your tank, so be cautious.

Also - be sure in checking capacity that the tank, any supporting frame, the full-tank amount of water, AND any bottom gravel are counted in the weight. Also seismic loading and tiedowns appropriate to your locale.

Also check your initial weight estimate - sounds low - at 28SF of bearing area (so 2x14 feet if 24" joist spacing), assuming minimum say 200# tank weight (and likely a lot more, especially if it has a decorative base), I get about 16 inch tank height - is that right ? Seems like that big a footprint tank would normally be 3-5 feet high - which would weigh several tons or more.

I certainly would not chance it without a good check - get a Structural Engineer (your Search the List category) to assess the strength of the existing structure and determine if it will bear it, and if so whether you need to build a structural "bed" for it to sit on to be sure the load is evenly distributed. You may need a "bed, at least "sleepers" (longitudinal timbers) anyway if the floor is warped, just to custom-fit the sleepers to the floor profile so the weight is evenly distributed over the joists and so the tank is not point suported, which could easily cuase it's failure. Cost probably about $300-600 for the inspection and and required remedial design - plus maybe a couple or few hundred $ for a handyman to later repair a few inspection holes for the engineer to check out the floor and wall construction and condition. Plus of course any cost for a contractor to build any remedial structural fix to carry the load. Obviously, putting this up against a load-bearing wall or in a place where remedial columns can be put down to ground will reduce your cost significantly - mid-floor location, while a nice centerpiece, is likely to get expensive.

PS - good idea, if design will handle it, to put a catch basin under that large a tank (looks like 275-300 gallons) - can be concealed in the "bed", made of heavy pond liner with large-diameter drain pipes leading out of it so anything short of a catastrophic failure might be trapped and drained away without flooding your house. For this purpose, with "clean" water, most locales allow drain pipes (I would run a couple of 4" ones minimum unless bed liner is capable of holding most of the water from a failure until it drains out) running down through the floor and between the floor joists and exiting through an outside wall to the outdoors, because this is for emergency drainage of a leak which would commonly flow outside under the walls anyway so in most areas does not have to lead to a sewer. Don't forget insect screening or better yet louvers at the exit if you do that, and consider (if in real cold area) how to limit drafting through the pipe, like a hanging flap that closes or clothes dryer type louvered exit point.

Answered 3 years ago by LCD

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