Help - building a concrete base in garden

[boilerproblems]

Hi all,

I would like to create a concrete base in the garden - as part of this, I have had to dig up a lot of existing re-inforced concrete (from a WW2 bomb shelter) which I would like to use in the base (rather than getting rid of it, which will be a nightmare).

As a result, I have dug a hole which is about 45cm deep. In order to accomodate all of the rubble from the bomb shelter, I have built shuttering which also extends about 30cm above the ground.

I know the depth is overkill, but it means I can avoid having to shift the rubble.

Here come the questions:

Can I just break up the concrete into small pieces (say the size of 2 pint glasses) and place in the hole, before pouring concrete in and levelling?

Do I need to have a subbase, or will it be ok if I have small pieces (as described above) before pouring the concrete.

What about any membranes (dampproof or weed proof).

The dimensions of the area to be filled with concrete are: 2.5m x 6m).

Any help appreciated.

 

[paul_v]

you haven't actually said what you want to use this "base" for. Can't advice if we don't know what kind of strength is required.

 

[boilerproblems]

you haven't actually said what you want to use this "base" for. Can't advice if we don't know what kind of strength is required.

Hi, apologies. It will be used for a shed (on one side), and then paved for a patio for dining table etc. I guess there might be an opportunity at some stage to just place a log cabin on there (but this is in the distant future).

To accomodate the shed/paving area, this is what someone suggested:

Break up the concrete and top up with type 1 mot.
25mm sand blinding followed by DPM and finished with 100mm concrete.

.

Would this be suitable? I am conscious that this implies that the hardcore/type 1 mot becomes the sub-base, but there will be a heck of a lot of type 1 mot to fill the gaps. If I take this approach, is there a maximum size the hardcore pieces can be? Will I need to ensure the layer of concrete/type 1 mot is compressed? Do I need a weed membrane as well?

 

[boilerproblems]

Hi all - any thoughts on this?

 

[rxbren]

i personally wouldnt use the broken concrete and thick pieces the size of two pint classes would not compact enough and leave too many gaps
id skip the concrete and use type 1 at least 100mm - if using more than 150mm compact it in layers of 100mm (some people use crushed concrete but im not a fan) then once compacted put a layer of 1200 gauge polythene down and pour the concrete a sheet of a121 steel mesh is optional then tamp down firmly smooth off arris trowel the edges and brush finish the top