• If you are planning on attempting a small DIY concrete job it is extremely important that you calculate the correct amount of concrete to order. Concrete is always ordered in cubic meters.

First off you need to identify what the new concrete area will be used for.

ie: Footpath, garden shed, driveway

Different concrete applications require different thickness’s.

Use this as a basic guide for square and rectangle areas

Footpath – 80mm thick
Small shed slab – 80mm thick
Driveway for standard size cars – 100mm

Use the formula below –

L = Length W= Width H = Height or thickness

(L) x (W) x (H)

driveway:

If the driveway is 5 meters long x 4 meters x 100mm thick

5x4x.1= 2 cubic meters of concrete required

The same formula can be applied to strip footings, steps etc.
To work out the required concrete for a triangle area the formula is as follows:

1/2 = half B = base H = height

1/2 (B)x(H) this gives you the square meters of the area, with this square meter amount the cubic meter volume can then be worked out

If a triangle has a base length of 5 meters and a height of 4 meters the equation would look like this

2.5×4 = 10 sq meters (2.5 is half of the base height being 5)

Now that we have the square meters of the triangle area we can work out the cubic meter volume

10 (sq mtrs) x.1 = 1 cubic meter

There are quite a few different types of concretes available inc. plain, coloured, exposed aggregate, terrazzo, limestone, light weight, eco concrete etc

There are a few main factors which affect the type of concrete required. Different applications may require more strength or a large aggregate size etc

For a standard driveway the type of concrete you would order is 25/14/80

25 = 25 MPa 14 = 14 mm aggregate size 80 = 80 slump

For a footpath the type of concrete required would be 20/14/80

For footing the mix would be 25/14,20/80

During winter or colder months the mix would also need to be a “Winter mix”. A winter mix has a low dose of accelerant in it to help speed up the curing time.

During summer a decellerant may need to be used to slow the concrete curing time down.

Paying careful attention to the points listed will help the DIY to not only save money on over ordering concrete but choosing the correct type of concrete to order.