Water tank on roof - question about weight

[ppmoore]

Hello,

I'm in the process of installing a rain water tank on my flat roof to store water to water the garden with during the summer. I've bought a

200 litre plastic tank (weighing 200 kilogram when full), and was wondering if flat roofs in general can take this weight. I was thinking of setting the tank on two 1 metre concrete beams, side by side, to spread out the weight, but these together with a concrete block I was also thinking of putting in the tank to stop it blowing away when empty, is also extra weight.

Can anyone advise?

Many thanks, Paul

[Brian Gaff]

I'd say no. Though it really depends on the roof.

Brian

[Andrew Gabriel]

You'll need to get a structural surveyor to assess this in conjunction with determining the roof structure. Note the roof also needs to support a depth of snow.

I had a structural surveyor check before I removed an upstairs wall which was not far from the storage tanks in the loft. Fortunately in my case, the water tank weight was spread across 6 of the A frame ceiling joists with a well sprung timber frame, so he said none of the upstairs walls were supporting it. Indeed, when I pulled off the coving, I found the wall didn't actually go right up to the ceiling, and had been built after the ceiling was plasterboarded ;-) But this is the sort of thing than needs checking first.

[Newshound]

I agree with the other posters, but instead of concrete how about two or more 3x3 tanalised fence posts, say 2 metres long. Set perpendicular to the joists, if you can determine which way they run. Rather than a concrete block inside you could bolt the tank on to the posts with coach bolts, penny washers, and silicone or mastic to seal.