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.

Read more: //www.diynot.com/forums/garden/help-building-a-concrete-base-in-garden.362404/#ixzz2QimDHOKP

 

[Alastairreid]

Whats the base for?

 

[boilerproblems]

Whats the base for?

Part of it will be used for a shed. The other part, I am planning on paving to use for a dining area etc.

 

[Alastairreid]

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

 

[boilerproblems]

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

Thanks.

The broken concrete - what is the maximum size of pieces that can go in? And once topped up with type 1 mot, do I need to get something to flatten/compress it?

Do I need to put anything down below the concrete/type 1 mot in order prevent roots penetrating through? We have removed as many roots as possible, but there is one root that is part of a tree we are planning on keeping that runs just under the concrete/type 1 mot. Is that likely to cause the whole base to raise/split?