Loft tank replacement platform question

[Wondering_Aloud]

Hi Everyone,

Wasn't sure whether this should go into plumbing or building but as it's the plumber that has to do tank replacements, I thought I'd put it in 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.

Any advice/words of wisdom, gratefully accepted.

 

[MeldrewsMate]

The nails are far too long, take them out and cut them down to 2.273" before hammering them back in...

But seriously, the nails are only there to keep the platform from wobbling over, they don't take any vertical load. If the 3x2s are screwed to the top of the 6x2s then extra stability has been added. If you want to add even more I suggest screwing a length of 3x2 to the wall, then replacing one or two of the existing 3x2s with slightly longer ones that reach this new piece of timber, then fix the parts together with screws or nails. 1" sheet for the tank support is admirable (as long as it's not MDF or similar!)

 

[Wondering_Aloud]

Hiya,

Thanks for that, I feel a lot more settled regarding the current set up but am aware that the two 25 gallon tanks are loading the platform up in a different way to the original round one. I think the nails may be shorter and I was making an assumption (always a mistake) I suspect the 3x2s have been screwed but I haven't had the platform out yet so can't be sure. My main problem is that although I'm happy with my plumbing, I don't know enough about platforms to be comfortable. I cross posted this on the building forum and someone suggested putting cross pieces in at each between the 6x2s so it forms a box, so I have a large length of wood in the living room.

I'd think it'd add a lot of stability but as I say, I don't know enough to be confident on it and I'm wary of the weight of water.

Thanks for your help.

 

[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.