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Published on 8/5/2017

Published by marketing@concretebroker.com.au

How much concrete, steel and accessories do I need?

And how much do concrete slabs cost in Australia?


 

 

Cover photo source : by Adriana Velásquez on Unsplash

 

Concrete broker was founded to give the Australian public the tools, resources and information necessary to purchase and pour concrete

 

 

How much concrete, steel and accessories do I need?

And how much do concrete slabs cost in Australia?

 

 

Whilst in Australia prices vary depending on supply and demand though here at concrete broker 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.

Let us take the example today where Joan and Paul 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 Paul some extra storage room for his tools, lawn mowing equipment and bar fridge. 

 

Step 1. Concrete

How much concrete do Joan and Paul 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 broker 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

Do I need any steel? Accessories?

 

Photo source : Juliette Leufke on Unsplash

 

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. 

Paul and Joan 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 broker we would recommend laying some plastic above Joan and Paul'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 Joan and Paul 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 Joan and Paul are going to have some left over after they have purchased the 2 bags of bar chairs required to fulfil their requirements.

Then Joan and Paul are going to need to place keyjoint 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 keyjoint, dowels, dowel serts and expansion joint they were able to control cracking within the slab.

How much is this 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. At concrete broker we are recommending Joan and Paul pay no more than $225 per cubic metre for their concrete as they are close to the plant in a relatively well built up area.

8 cubic metres x $205 = $1,640 plus gst

Steel and accessories

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 keyjoint, dowels, dowel serts and expansion joint 
3 x $120 = $360 plus gst

The total cost of concrete, steel and accessories is $2,640 plus gst

Joan and Paul don't have a truck or trailer to pick up the mesh and accessories an 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 $2,730 plus gst.

Having rung around, even though the ground where the slab is located is relatively flat,  Joan and Paul have been advised to purchase $270 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 slab. As a consequence the costs of materials for Joan and Pauls concrete slab for their outdoor shed stand at $3,000 plus gst

What about a concreter? And how much do they cost?

 

Photo source : Adriana Velásquez on Unsplash

 

Step 3. The concreter

Paul is a retired accountant and Joan is a school teacher. Suffice to say concreting is not something they make a living from. At concrete broker 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. Joan and Paul have none of these tools or equipment.

At concrete broker the concreters we recommend may or may not be licensed, depending upon the state in which you live. Paul and Joan are in NSW where choosing a concreter with a license gives them the surety of knowing their concreter is insured. Here at concrete broker 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 Joan and Paul have their concrete shed slab estimate from concrete broker at $5,520 in total or approximately $77 per square metre.

NB. For the purpose of Joan and Pauls concrete slab all prices are exclusive of GST.  
When GST is added the cost per square metre cost is increased to approximatel $84 per square metre.

 

Photo Source : Clark Young on Unsplash

 


The prices quoted herein are an average researched from concrete broker members throughout Australia and should be taken as a guide only. At concrete broker we recommend you seek advice from concrete professionals within our network, or simply email us info@concretebroker.com.au where we can provide three product and service providers within your area. 

 

Related Articles : 

 

How to lay a concrete slab : https://www.concretebroker.com.au/Blog/View/16

I need concrete. How do I choose a concrete plant? : https://www.concretebroker.com.au/Blog/View/24

 

HAVE A CONCRETING PROJECT?

If you are ready to go with your next concreting project fill out a quote form here and at concretebroker we can put you in touch with a concreting expert near you. In fact we'll go further, we'll match you with 3 concreting experts.  Assess their quotations, read about their business online at concrete broker, and make an impartial, calculated decision.

 

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Tags: accessories bar chairs concrete concreter keyjoint plastic shed slab steel


This article was written by marketing@concretebroker.com.au all rights reserved. The views and opinions expressed in this article are those of the author(s) and do not necessarily reflect those of concretebroker.com