Cold water tank loft support

28 Aug 2012
Reaction score
United Kingdom
Hi all,

I'm looking to fit a Polytank Cold Water Coffin Tank (70 Gallon) into our loft to replace the existing 40/50 gal circular tank that is already up there. The dimensions of the new tank are 1650 x 610 x 500mm

The new tank will go up the loft hatch fine and I am sure the old one will come down ok but I was wondering where to position it and would the loft joists would take the weight of the new 70 gal tank?

I was thinking I get some ply wood and sit it on that going across the joists but would this be enough to support it or should I look to lay wood across the joists and put on top of that.

Also I don't think there is a load bearing wall that I can fit it over as the walls on the first floor are stud walls.

Any suggestions or advise would be greatly appreciated.
Sponsored Links

Use 2 lengths of 6" X 2" on edge so they span at least 4 joists and ply on the
top of them to support the base of the tank.
This may sound a dumb question but do you need to lay the 6"x2"s flat on the 6" side (so standing 2" up) or lay them on the 2" edge (so standing 6" up)?
Sponsored Links
I've got the tank in the loft and I have an idea of where I would like to put it BUT the concern I have is will it be strong enough to hold where I want to position it.

Its a semi detached house. The roof is a dormer roof and our loft has two sides bricked up to the top (one is the gable end the other is the join to the house next door) and the other sides are where the dormers are which is timber frames with stud walls below. The middle part of the loft has been border up.

I would like to position my new 70 gallon polytank as close the the edge where the rear dormer is (so centrally but away from the boarded middle of the loft and pushed as close to the edge of the loft).

I can see the joists going parallel to the gable and there is one length of timber (going cross joist if that's the correct term) which is 5 inches deep by 2 inches wide. I was thinking I would get some more 5x2's (perhaps 4 or 5) and screw them in then put a 18mm bit of ply on top of this then sit the new tank on top of that?

Does that sound ok and the the loft being able to take the weight of the new tank in this position? Are there any engineers on here that can give me a thumbs up on this?
Can you position it over an internal wall? If not you will have to be content with the fact that the old tank stayed there for so long.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local