Bath Weight?

Discussion in 'Builders' Talk' started by Virtual Voodoo, Apr 27, 2008.

  1. Virtual Voodoo

    Virtual Voodoo New Member

  2. Captain Leaky

    Captain Leaky New Member

    360 litres = 360kg + you + wifey + bath etc
  3. Captain Leaky

    Captain Leaky New Member

    over half a tonne probably altogether!:O
  4. lojo

    lojo New Member

    most of us builders (I may be wrong) will tell you that the joist span/joist size is well within the limits, and that sort of loading is not unreasonable, however that assumes the weight is spread evenly on a ply subfloor(ie. feet not inbetween joists on a knackerd pine floorbrd)and also assumes the timbers are in good condition, have'nt been half milled out by sparks and plumbers, and have suitable bearing (I saw a bathroom issue once where decent sized joist all sat, notched over a 2x1 cut nailed to the brickwork!)

    however unless someone here can offer some maths, try the engineers forum (and get them to sign it!)
  5. Virtual Voodoo

    Virtual Voodoo New Member

    Forgot to say that the floor material is 22mm green chipboard.

    I'm assuming that I'll have to get a Chippy to make a suitable stud frame to support the bath and therefore the weight will be spread across multiple joists.
  6. Measure2cut1

    Measure2cut1 New Member

    Baths should only rest on their feet and not a frame.

    You could do what I did once. I had an old metal bed frame and hacksawed the ends off the angle iron sides and used those under the feet to spread the load. Probably was not necessary but I had oldish floorboards.

  7. ecm

    ecm New Member

    VV, you need to double the joist(s). I've done the calcs but had to make some assumptions as you didn't provide all the info required. Here you go,

    Assumed dead load of bath=75kg
    Assumed surface area of bath=2.4m2
    Total dead + imposed load = 435kg / 2.4m2 = 181.25kg/m2
    181.25kg/m2 = 1.77kN/m2

    Assumed joist span of 3.6m @400mm centres C16 220x47.

    TRADA tables have max permissible span of 3.99m (C16 220x47 @400 centres) for dead load more than 0.50Kn/m2 but not exceeding 1.25kN/m2. All joists beneath a bath should be doubled as per 4.1.4 of the TRADA span tables.

    From TRADA span table:
    The UDL of a full bath can exceed 1.5kN/m2 (you have 1.77kN/m2 with a full bath) imposed load for which normal floor joists are designed. This is why Section 4.1.4 says that joists beneath a bath should be doubled.

    So all things considered I would give some serious thought to doubling up the joist(s) under the bath.

    Hope you can follow that.
  8. brickbaron

    brickbaron New Member

    ecm knows his stuff. also all baths require patresses to be installed under the feet to spread the load, most installers don't do it but i think it takes 5 seconds and it makes sense. frames around baths are only there to carry bath panel and not to carry weight all baths are designed to be supported via the bath feet and therefore you need only worry that they are fixed properly and on patresses. dont know whats under your bath ie ceiling height but you could consider halfing the span of the joists by installing an RSJ transversely, if you can go masonry to masonry,get it?
  9. Virtual Voodoo

    Virtual Voodoo New Member

  10. ecm

    ecm New Member

    Not sure if doubling of the joists is entirely
    practical emc. :(

    How about this version of a round bath which is
    designed to go in the corner of the room and hence
    would create less stress than mounting the other
    model in the center of the room?

    The specs for that bath show the same surface area (look at the PDFs on the dimension page) and capacity as the first one so the calcs will come out the same for the loading on the floor. The fact you want to put it in the corner rather than the centre of the floor has no bearing on the loadbearing capacity of the floor joists in those locations - it makes no difference.

    Now I know you say it's not entirely 'practical' to double up the joists but your looking at spending the best part of £700 on your bath and a piece of C16 220x47 @4000 is going to cost £10+vat. What are causing you the problems running another joist(s) alongside the existing(s) and doubling up? There may be an 'easy' way to do this.
  11. Virtual Voodoo

    Virtual Voodoo New Member

    Hi ecm

    Are you talking about bolting additional joists next to the 4 or 5 that will be directly underneath the bath?

    That might not be to difficult to do, but setting them in to either side the walls, if required, may prove messy?
  12. ecm

    ecm New Member

    VV, I reckon you will probably away with doubling up 2 joists, (3 at the maximum) if you look at the 'footprint' dimensions on that bath. You only need to double up directly under the bath.

    Your best option is to chop into the brick/blockwork to provide a bearing for the new joist and bolt through to the existing joists. Alternatively, you could use hangers, slightly offset from existing joists (for obvious reasons), pack-out, and bolt through (but I don't like that idea really and it depends on the fixings you can get in the wall.

    hope that helps

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