How big a water tank can I put in loft?

[locoloic]

Hi all,
So, I have 6x2 beams in my loft, spanning a little over 20ft.

assuming no supports part way along the span, what is the safe loading per beam midway along the span?

I’ve got a water tank up there already, but looking to change it out to a direct pressure. Just wondering how big I can go.

thanks all.

 

[Deleted member 174758]

6 x 2s (145 x 44mm) C16 joists on 400mm/16in centres are supposed to clear span only 3.1 metres (circa 10ft) with a 0.25kN/sq.metre dead load (or about 2lb/sq.ft) according to my joist tables. Your ceiling centres are more likely to be 600mm, so you are going to be pretty limited on the additional load you can carry, especially when you consider that a gallon of water weight 10 lbs and that a 250 ltr (55 gal) tank holds circa 550 lbs (or about 1/4 ton) of water without taking into account the weight of the tank. TBH I think you need to talk to a structural engineer, but don't be surprised if he tells you that you'll need to massively beef-up your ceiling joists to carry any additional load

 

[foxhole]

Does the tank have to go centrally?, you can use more than one smaller tank linked to spread load.

 

[Leofric]

Structural engineer to advise.

 

[Chunkytfg]

FWIW i'm in the process of doing this with a 250L unvented tank.

SE has calculated 2 lots of 3 lengths of c24 8x2 bolted together side by side spanning 5.8m.