Wooden floor load capacity

Discussion in 'Engineers' Talk' started by Andrew987, Jul 7, 2022.

  1. Andrew987

    Andrew987 New Member

    Hello folks,

    Possibly a bit of a random question here, but here goes.

    I've recently acquired myself a 640 litre fish tank that I'm planning on putting in my living room. I completely neglected to consider the weight of the thing before buying it, and I'm wondering if my floor will hold it.

    Unfortunately the living room is the only downstairs room with a wooden floor. The tank is 6 foot wide with a flat base rather than legs so the weight would be distributed over 4 joists (I think they're 16" apart), and it would be up against a solid brick wall between me and my neighbour.

    To further complicate matters, on the opposite side of the room which is 3m wide at that point, there's a piano and an organ which are close to 200kg each.

    So, is sticking another 700kg (ish) on my floor going to make it collapse and flood my house? (I suspect it will!) :confused:

    Any advice appreciated,
  2. MRY

    MRY Screwfix Select

    Pictures are always useful... but assuming you can support the bottom of the tank properly, why not have some friends around, and stand them on the floor where your fish tank might go, and see whether or not they fall through it? Perhaps not very good friends if you're worried...
    Neil1987 and Andrew987 like this.
  3. Jord86

    Jord86 Screwfix Select

    In the absence of any engineers, I’d reinforce your floor joists and notch 4x2 props under them bearing down on the subfloor.
    Andrew987 likes this.
  4. Severntrent

    Severntrent Screwfix Select

    Without joist size and span question cannot be answered
    Andrew987 likes this.
  5. Greentram

    Greentram Member

    640 litre tank will weigh about 650kg. Domestic floors are generally designed for a uniform imposed load of ~150kg/m2 (30lb/ft in old money). Even allowing for an unloaded space in front of the tank equal to the tank size you're probably pushing it, but as previous answers it's not possible to give a definitive answer without knowing the joist size, span and spacing. If you're lucky the room size might mean that the sleeper walls (assuming it's a suspended ground floor) are closer together than necessary making the floor stronger than necessary.
    Andrew987 likes this.
  6. stevie22

    stevie22 Screwfix Select

    In the real world you are highly unlikely to have any problem. The chances are there will be sleeper walls and the organ & piano won't actually affect the area you are looking at and you are at the end of the joist either way.

    Design codes for timber are based on deflection not strength so the issue would be the floor bending too much not breaking.

    I'm actually sitting in my office looking at floor to ceiling book cases loaded to the gunnels and wondering if I'm brave enough to work out their loading (first floor)
    Andrew987 likes this.
  7. Andrew987

    Andrew987 New Member

    Thanks for the replies everyone, much appreciated.
    I'll try and get under there over the weekend and see exactly what's there.

    My only slight issue is, I've just finished redecorating the living room and my other half might kill me in my sleep if I start ripping floors up now!

    Assuming I survive, I'll report back with my findings.
  8. Andrew987

    Andrew987 New Member

    So I've done some poking around and here's what I have (see attached diagram (not to any kind of scale!))

    The room is 2.52m wide
    The joists running front to back are 2"×4" spaced at 14" on centre.

    As luck would have it, 1.4m from the back wall there's a solid wall supporting the joists, which is pretty much where the middle of the tank will be, so I'm assuming this wall will be more than capable of carrying the load. 20220709_171201.jpg 20220709_171201.jpg

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