Loft tank replacement platform question

[Wondering_Aloud]

Hi Everyone,

Wasn't sure whether this should go into plumbing or building but I posted in plumbing and lots of views but no replies so I've reposted here.

Our loft tank has stretched to the point where it's a couple of inches wider than its lid and while I have plumbed in copper and plastic during a spell in the the water industry, I'm less sure of the platforms the tanks sit on.

The original tank was a round, 50 Gallon that must have been loaded in through the roof before it was fitted as it sure as hell won't go through the loft hatch. Being a 90's build, it has a trussed roof and after making a cardboard model of a 50 gallon coffin tank, it's obvious that it will fit through the hatch, but won't reach the platform so two 25 gallon square tanks with link pipes is the practical option.

While I've been up surveying the situation, I've had a good look at the platform the tank sits on. There are two 4x4" beams that span the house, which I'm assuming are load bearing. Across them, are two 6x2" beams one near the wall that divides the house from it's neighbour, and the other about 3 feet out. Between those two beams are 3 3x2's, upon which sits an inch thick platform that supports the tank.

The thing that puzzles me is that the two six inch beams that are sat on the load bearing spars are on edge, and appear to be held in place by a single six inch nail at each point where they sit on the 4x4's. Is this normal? I'm assuming that the idea is that the weight of the water, about 230kg applied across the platform, keeps the beams underneath it in place but 4 six inch nails holding the whole plot in place doesn't seem enough somehow. As the old tank used to sit centrally over the centre 3x2 and the new tanks are going to be spread across the entire width of the platform, I can push a couple of extra beams under to provide better support but is it worth chocking up the beams? They've been there since the house was built with the old tank on and they were fine them but while I have the tanks out, it'd be a good time to add some bracing if required.

Hastily sketched diagram attached.

 

[Notch7]

Id be tempted to put a 6 x 2 down the middle and 1 at each end to make a solid box all screwed together, with brackets to hold it if needed.

3 x 2 doesnt that big, Id put a few more in, maybe screw 2 together as a double, I under each tank.

Is that overkill?

 

[Wondering_Aloud]

Id be tempted to put a 6 x 2 down the middle and 1 at each end to make a solid box all screwed together, with brackets to hold it if needed.

3 x 2 doesnt that big, Id put a few more in, maybe screw 2 together as a double, I under each tank.

Is that overkill?

 

[Wondering_Aloud]

That's kind of what I've been thinking. I dontddo much building but when I do, I tend to over engineer. On the one hand, it was there for 20 years with the old tank on it, but on the other, it does seem a bit lightweight for a quarter ton load. I was considering leaving the existing set up but putting in a couple of extra 3x2s and cutting a set of triangular braces out of 6x2 and screeing then into the load bearing 4x2s, butter up against the 6x2 beams to keep them upright. Hopefully that would avoid having to remove the platform which is cut around the roof trusses

 

[Wondering_Aloud]

One other possibility I had thought of was to add 2x6 boards along the sides to make a box and screw 4x4 blocks into the corners to hold it together. The loft hatch is awkwardly positioned for getting an additional 3m 6x2 into the loft but it I'll only find out by trying.

 

[Wondering_Aloud]

Hi all,

Just a quick update in case anyone else is asking the same question and would like to know what happened.

I posted on two forums and got several very helpful suggestions and in the end, the fact that the existing platform had lasted a fair time with the old tank on it meant it could obviously take the weight of water, and that the redistribution of load was the real question. The two upright boards were being stabilised by the 3x2's nailed across their tops so in the end I added another couple of 3x2s in between the existing ones to better support the wider footprint of the square tanks and then placed to 6x2 inch boards between the long 6x2s, fixing them in place with M6 coach bolts to blocks screwed to the main 6x2s. This took any wobble out of the setup and as the original setup must have been in a steady state as it hadn't collapsed, the actual load on the new boards should be trivial.

End result - platform is solid and stable and heavy duty enough to let me sleep at night.

Thanks again to all who replied.

 

[John D v2.0]

A bit late but deflection wouldn't really be an issue with a water tank platform as the are no finishes to worry about. The tank does need to be well supported so the spacing needs to be narrow enough. Regarding the lateral stability yes 6 by 2s on their side isn't perfect but in a situation without sideways load it would be extremely hard to overcome the stability and knock it over. A noggin at each end screwed into the 6 by 2 would be plenty if you're worried