Published on 4/3/2021
Published by email@example.com
What does a concrete slab cost?
CHECK OUT THIS EXAMPLE OF A CONCRETING COST ESTIMATE
1. How much concrete, steel and accessories do I need? and,
2. How much do concrete slabs cost in Australia?
Let concrete shopper provide an estimate for you.
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At concrete shopper we are going to take a look at how to work out what you require in your concrete slab, and roughly how much it shall cost. Obviously this is a quick ready reckoner guide only as individual costs change depending on your topography, sub base and your demographic. Whilst in Australia concreting costs and concrete prices do vary depending on your location.
Let us take the example today where Jill and Terry want to build a small shed to house their boat and caravan. They need to lay a 9 metre by 8 metre concrete slab to afford Terry some extra storage room for his tools, lawn mowing equipment and bar fridge.
Step 1. Concrete
How much concrete do Jill and Terry need?
Let's work out the square metres involved :
9 metres x 8metres = 72 sq. metres
Assuming the slab is 100mm (4 inches) thick, multiply your sq. metres by .1 to work out the cubic metres of concrete required
72 sq. metres x .1 = 7.2 cubic metres of concrete
Then to be safe add 10% for an uneven sub base, spillage and other variables
7.2 cubic metres of concrete x 10% = 7.92 cubic metres of concrete, or 8 cubic metres when rounded up
What strength concrete do they require?
20 or 25 MPA concrete would suffice for your shed, as there are not going to be any heavy vehicles traversing over the concrete. Though here at concrete shopper we recommend you always choose slightly higher strength concrete where affordable, as stronger concrete costs only approximately $5 per cubic metre more, and therein significantly reduces the chances of long term cracking under weight, deterioration and weathering. Additional water added on site may reduce the concrete's strength as well so it is better to be sure than sorry.
How much is this concrete going to cost?
Concrete in Australia can cost anything from $150 per square metre to $300 per square metre depending on where you live and the distance you are from a concrete plant. In this example Jill and Terry pay no more than $250 plus GST per cubic metre for their concrete as they are close to a concrete plant in a relatively well built up area.
8 cubic metres x $250= $2,000 plus GST
Do I need any steel? Accessories?
Step 2. Steel and accessories
It is recommended the concrete slab is supplemented with steel reinforcing mesh to increase the flexural (tensile) strength of your concrete. Mesh comes in 6 metres by 2.4 metre lengths in varying diameters.
Terry and Jill would be well advised to purchase either SL 72 or even the slightly stronger SL 82 reinforcing mesh, to further strengthen their slab.
To work out how many sheets of mesh required we divide the square metres of the slab by 12.2.
72 sq. metres divided by 12.2 = 5.9 or 6 sheets of mesh when rounded up
What about accessories?
At concrete shopper we would recommend laying some plastic above Jill and Terry's sub base to prevent moisture and damp rising up into the concrete and steel reinforcing above. Plastic usually comes in 50 metre by 40 metre rolls with coverage of 200 square metres so Jill and Terry shall have some left over to use elsewhere in the garden bed or around the house.
To raise the mesh up a bag of plastic bar chairs is required as the reinforcement must be at least 5cm above the compacted base and 4 cm or so below the top of the slab. 50/65 bar chairs would suffice. Bar chairs come in bags of 100 and you require about 18 chairs per square metre so again Jill and Terry are going to have some left over after they have purchased the 2 bags of bar chairs required to fulfil their requirements.
Then Jill and Terry are going to need to place key joint through the middle of the 9 metre section of their slab to ensure their concrete doesn't crack when in a hardened state. By cutting a groove through the centre of the slab and filling it with key joint, dowels, dowel inserts and expansion joint they were able to control cracking within the slab.
Steel and accessories cost
SL 72 and 82 are going to cost approximately $80 per sheet
6 sheets of SL82 mesh x $80 = $480 plus GST
1 Roll of plastic at $120 per roll = $120 plus GST
Two bags of 50/65 bar chairs at $20per bag are 2 x $20 = $40 plus GST
Three packs of 3 metre key joint, dowels, dowel inserts and expansion joint
3 x $120 = $360 plus GST
The total cost of concrete, steel and accessories is $3,000 plus GST
Jill and Terry don't have a truck or trailer to pick up the mesh and accessories and they have been quoted a $90 delivery fee taking the total cost of materials for their 9 x 8 metre concrete slab in Australia to $3,090 plus GST.
Having rung around, even though the ground where the slab is located is relatively flat, Jill and Terry have been advised to purchase $360 worth of crusher dust (including delivery) to line their sub base at 5cm thick in order to provide a firm, well drained base for their concrete shed slab.
As a consequence the costs of materials for Jill and Terry's concrete slab for their outdoor shed stand at $3,450 plus GST
What about a concreter? And how much do they cost?
Step 3. The concreter
Terry is a retired accountant and Jill is a school teacher. Suffice to say concreting is not something they make a living from. At concrete shopper we recommend they hire an experienced concreter. The concreter can bring the expensive tools and equipment required to lay and complete the concrete for their shed. They have plate compactors to compact the crusher dust, formwork within which to form the concrete slab, ties and tools to place the steel, screeds and trowels place the concrete and helicopters (electric trowels) the finish the concrete and give it an even surface. Jill and Terry have none of these tools or equipment.
At concrete shopper the concreter's we recommend may or may not be licensed, depending upon the state in which you live. Terry and Jill are in NSW where choosing a concreter with a license gives them the surety of knowing their concreter is insured. Here at concrete shopper we recommend they allow between $30 and $40 per square metre when budgeting for concreter expenses. Someone may quote them less though we recommend paying a good concreter who comes recommended more money per square metre to ensure they receive the end product they are searching for, that being a sound shed slab upon which to house their boat and caravan, for good!
Cost of concreter 72 square metres x $35 = $2,520 plus GST
Therefore Jill and Terry have their concrete shed slab estimate from concrete shopper at $5,970 in total or approximately $83 per square metre plus GST.
NB. For the purpose of Jill and Terry's concrete slab all prices are exclusive of GST.
When GST is added the cost per square metre cost is increased to approximately $91 per square metre.
Nb. The prices quoted herein are an average researched from concreting professionals throughout Australia and should be taken as a guide only.
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