Concrete mix for shed base

by EdwardH
(Nottingham)

Morning All, I'm looking to find out what mix of concrete and ballast I need for the base foundation of my 4m x 4m log cabin.
The concrete will be reinforced with a metal grid.

I am told the standard is 5 to 1, what would you advise?

Thanks

E

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Using ballast for shed base concrete
by: John

Hi Edward,

DIY concrete is generally mixed by volume and comprises 1 part cement, 2 parts sand and 3 parts coarse aggregate.

As you are using ballast which is a mixture of sand and coarse aggregate then the ratio of 1 part cement to 5 parts ballast is correct.

To get a good strong mix don’t go to heavy on the water.

Regards

John

PS.

Just a quick thought, how much concrete are you using?

For a 4x4m base @0.1m thick that would be 1.6m3.

Had you considered using a volumetric concrete mix?

A volumetric concrete mix is different from normal ready-mix concrete.

For normal ready-mix concrete drum mixer, all the concrete constituents are fed into the mixing drum at the batching plant. You have to order exactly the right amount. If you don’t order enough the base will be thinner than needed. If you order too much the company charges you to take it away or you have to find somewhere to put the extra volume! This can be quite stressful at the end of a concrete pour.

For a volumetric mix the lorry has separate compartments for the sand, aggregate, cement and water. The driver of the lorry/mixer is in control of the mixture and he can start and stop as needed. You don’t get stuck with extra unexpected concrete like you can when concrete is supplied in a mixer direct from the batching plant.

This method of concrete supply is slightly more expensive than ready-mix concrete, about £10/m3. I think because they are selling it in smaller amounts rather than by the whole truckload. But the convenience is worth it.

Is diy concrete cheaper than ready mix?

The benefit of ready mix concrete over diy concrete is the saving in time and effort. If you are pouring 1.6m3 of concrete from a ready mix supplier this will cost about £294.

To buy the materials for 1.6m3 of concrete, 2.67 tonnes ballast and 21 No. 25kg bags of cement, it would cost about £200. Plus hire of a mixer if you don’t have one.

The 1.6m3 will involve a days work at least for two diy’ers. You are shovelling about 3 Tonnes of material, by hand and then there is all the mess and cleaning up afterwards.

With a volumetric mix you are only limited by how quickly you can barrow the mix from the truck to the site. Probably about 20 mins.

What would you choose a day of hard labour and so-so quality over 20 minutes, consistent quality and getting on to the next part of your build?

The extra cost for mixing the concrete yourself is just under £100, you could easily spend that on a couple of visits to the chiropractor to sort out your back afterwards!

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