Laying a pad in 2 stages

[thomp1983]

Hi all,

I need to lay a concrete pad to support a large water butt.

The pad will be 1200mm w x 700mm l by 100mm deep.

It's on a slightly sloped piece of ground, is there any real issue laying it in 2 pours so I don't have to make a tapered frame to pour it into?

I'll be using all in one high strength concrete.

Thanks
Chris

 

[noseall]

Hi all,

I need to lay a concrete pad to support a large water butt.

The pad will be 1200mm w x 700mm l by 100mm deep.

It's on a slightly sloped piece of ground, is there any real issue laying it in 2 pours so I don't have to make a tapered frame to pour it into?

I'll be using all in one high strength concrete.

Thanks
Chris

Like two halves of a book or two layers of cake?

Book ok - cake no. Just make sure you trowel the joint tight.

 

[thomp1983]

It would be 2 half's of a cake I'm guessing, so basically lay the bottom say 50mm, let it set off then pack the former up so the top is level then lay the second half and use a board to tamp/drag across the top of the former to leave a level top.

If that's not acceptable then I guess I'll have to mess about tonight cutting some firrings in effect to allow the top of the former to finish level

 

[^woody^]

In context of this being for a water butt, no problem. Key the surface of the first layer.

 

[noseall]

In context of this being for a water butt, no problem. Key the surface of the first layer.

I'd just be wary of the summer sun and the thinner concrete layers.

 

[^woody^]

"Too hot for concreting". You don't hear that often enough.

 

[thomp1983]

The water butt in question holds 1200 litres so it does amount to a decent bit of weight when full.

My plan is to lay a level concrete pad to sit it on and attach the top to the wall of the house using resin fixings to stop it moving.

So based on the above I need the pad to be strong, if that means I need to make the former and lay it in one go then that's what I'll have to do, I was just trying to save a bit of messing about with the former but it's not worth it if it's going to compromise the overall strength.

 

[noseall]

The water butt in question holds 1200 litres so it does amount to a decent bit of weight when full.

Spread over the base and not point loaded, right?

 

[noseall]

It would be 2 half's of a cake

Make sure you wet the recipient layer before spreading the conc' and then drape a wet sack over it and keep it damped.

 

[thomp1983]

Yes spread, the sizes I put in first post will leave about 50mm all around it.

It's like that

 

[thomp1983]

So I've managed to make a former that will allow me to do 1 pour and get it level.

Next question is if I make the mix using all in one ballast in plastic bags and cement, what ratio do I want to be using given it needs to support about 1200kg when the water butt is full, I'm guessing stronger than the usual 1:4 ratio?

I need 0.12 cubic metres to fill the former so if I'm right that would be 0.12x2400=288 I can then divide that by whatever ratio I require and use that to calculate the amount of cement/all in one ballast I need?

Thanks
Chris

 

[noseall]

So I've managed to make a former that will allow me to do 1 pour and get it level.

Next question is if I make the mix using all in one ballast in plastic bags and cement, what ratio do I want to be using given it needs to support about 1200kg when the water butt is full, I'm guessing stronger than the usual 1:4 ratio?

I need 0.12 cubic metres to fill the former so if I'm right that would be 0.12x2400=288 I can then divide that by whatever ratio I require and use that to calculate the amount of cement/all in one ballast I need?

Thanks
Chris

You've barely even got 0.1 of a cube of conc (1.2 x 0.7 x 0.1= 0.84m³. You are probably looking at about 8 x 25kg bags of ballast and two 25kg bags of cement. Mix it (well) at a ratio of 6:1 or a bit stronger if you want. I'd take one of the bags of ballast out and add a bag of sharp sand so as to make the mixes a bit more fatty and mix at say 5:1.

 

[^woody^]

1

 

[John D v2.0]

Just out of interest how much is that water butt costing you?
I did a similar but ugly equivalent - a 1000L IBC propped up on 3 old pallets sitting on a few spare block pavers on the soil. And wrapped in some black DPM.
It works well but at 2-3 pounds a cubic metre for water I won't get my money back for about 50 years!

 

[cdbe]

Looks like the one in the picture is happily sat on a couple of 2x2 flags.