Ballast instead of scalpings?

[jon92]

I'm about to concrete a 8x6 shed base and have put a layer of hardcore over the soil where I've dug down about 6". Although the hardcore is about 3" deep overall and fairly well broken up I thought I should fill in any minor gaps and level the surface, so I was wondering if I could use ballast for this rather than scalpings. No reason other than I have far more ballast than I need and it seems difficult to obtain small amounts of scalpings.
Is there any reason not to do this? Or is it ok to skip that stage altogether and concrete direct onto hardcore?
Thanks for your help.

 

[LanceCorpralJones]

I would have thought that the hardcore should be about 6 inches deep (150mm) and well compacted, to refusal. Ballast should be OK mixed in with the hardcore, as long as it is well compacted.
The other important point though, is that you should remove all the topsoil so that there is no further subsidence of any organic matter beneath the hardcore.
It is only a shed but you haven't mentioned it's intended use.

 

[jon92]

Thanks, it's only a garden shed so nothing heavier than a lawn mower in it. 6" seems a lot, I hope it won't need that much or I've got some more digging to do.
I'm not sure what 'refusal' means in this context - can someone enlighten me please?

 

[KenGMac]

jon92, Hi

In general terms, most construction / building specifications state. [they do go on a bit]

1/. remove the top soil, generally a change in colour from black soil to another colour, this other colour depends on the area of the UK you live in, another give away is the lack of roots in this second coloured strata.

2/. Compaction of Hardcore, [generally] compacted layers shall be not greater than 300.MM in depth, and compacted by a suitable device, generally on small work a whacker plate.

Refusal is generally taken to be when the material being compacted actually refuses to be further compacted and driven into the sub soil

As an aside, sand is at times used to give a fine surface finish so the DPM can be placed on to the surface, the sand is a buffer between the sharp pointed bits of Hardcore and stop any puncturing of the DPM by the Hardcore.

Hope in some way this assists?

Ken.

 

[maltaron]

Its a garden shed!! 3" hardcore and 3" concrete is plenty and ballast is fine.
Most garden sheds are set on slabs laid on the ground!

 

[jon92]

Thanks all for your help, I'm going with 3"/3" using ballast to top up and fill in the hardcore. My method of compacting consists of hitting it with a club hammer and stamping on it, I hope that will suffice but we'll see in a few months' time!

 

[noseall]

You are doing fine with your 8' x 6' shed.

LCJ thinks you are after a Building Control certificate.