Concrete Slab costs: New Zealand Pricing Guide 2024

At Tidy Slabs HQ, customers ask questions like “How much does a concrete slab cost in NZ?”, “How much does a concrete foundation cost for my house?”, “Can you give me a ballpark estimate for my slab?” or “can you give me a concrete slab pricing rate sheet?” 

When it comes to concrete slab pricing in New Zealand, it’s hard to give a concrete (excuse the pun!) answer and I'll explain why. At the end of this article, you’ll be more informed as to what your slab will cost. I’ll give you some ballpark figures and some things to consider when planning your concrete slab.

Before I begin, when I talk about concrete slab costs, this includes concrete pads, concrete foundations, and concrete floors. They are all the same to us.

Firstly, I need to mention three things we can’t control that will influence your pricing.

  1. Location: Depending on where in the country your foundation needs to be built, the raw material and labour costs may very well be different. Generally, this will be governed by the distance to cart materials to your location as well as access to skilled labour in your region.
  1. Your section's ground condition: We can’t give you a comprehensive breakdown of concrete slab pricing without mentioning the varying ground conditions throughout New Zealand. The ground under your slab and how it’s ‘interpreted’ by the ‘experts’ can impact the overall price of your foundation greatly.  To make it more confusing, each Engineer (as well as each individual council) will interpret the ground, and how MBIE’s guidelines on liquefaction, expansive soils and flood zone risk will be applied, differently to the next. So what does this mean for you? This adds more ambiguity to calculating the cost of your concrete foundations. It is a bit of a moving target as to what the cost impact may be. We know this doesn’t sound all that comforting, however the best piece of advice we can give is to engage a slab contractor as early as possible - they are not geotechnical engineers, but they certainly know what is working in each region. The good ones will help you to navigate the process and give useful advice on constructability as you are presented with options by your consultants.
  1. Building code changes. Yes, New Zealand's Building Code insulation rule changes. The latest H1 insulation rule changes will most likely affect your concrete slab cost. Our comprehensive guide to these changes is coming shortly.

Well, all of the above will affect your slab price. Below is a list of common cost components that’ll help give you a realistic cost for your slab. So here goes…

The five main costs that effect your residential concrete slab price

Once we’ve added all the materials and labour, a concrete foundation (slab) for a stand-alone house can cost anywhere from $155 to $300 per square metre. On top of that you will need to think about the earthworks and piling costs, which again depending on the design, can vary greatly. Why is there a big difference in price per square metre? Here’s a list of factors that will impact the costs of your foundations… 

  • Total square metres of the slab - A portion of slab set-up costs are fixed. If the area is under 150m2 or so, the m2 rate will cost more to cover those fixed costs. For slabs over 150m2 the m2 rate starts to flatten out.
  • Ground conditions under the slab - After the area of the slab, this is the greatest contributor to the price. If the ground meets the building code definition of “Good Ground” and TC1 (Technical Category 1, which means that future land damage from liquefaction is unlikely) then you are in luck - costs will be fairly consistent.  However, if your ground is soft or it is prone to liquefaction (solids can turn to liquid) - then you could add in piles, or significant earthworks to the bill.
  • The structure above the slab ( Is it one story, two-storey, using timber cladding?) Single-story timber-clad house = lowest cost foundation Three-story brick veneer cladding = highest cost foundation
  • What foundation system has been designed Conventional? Pod floor, Plastic Pod floor?
  • If you have in-floor heating and/ or polished concrete floors your slab will cost more.
  • Which Climate Zone are you in? 
  • Using the Schedule method for calculating your H1 requirements II you live in the North Island (Climate Zone 1-4) you will need to achieve an R-value of 1.5 which generally will require additional under slab and edge insulation. If you live on the South Island (Zone 5 and 6) you will need to achieve an R-Value of 1.6 and 1.7 respectively
  • Using the Calculation method for calculating your H1 requirements You may not need any insulation at all, it will come down to what R-Value the other elements in the build achieve. Talk to your designer or us for advice on how to do this.
  • Do you have inslab heating? You will need an R-Value of 2.5 and will most definitely need edge insulation. If you do need insulation - depending on the target R-Value it will cost an additional $30-$60 per m2.
  • If there are specific floor heights that need to be achieved for council requirements. This could be due to being situated near a river flood zone.
  • If there are multiple heights within your foundation- this slab will cost more.

For example, if you're needing a 160m2 standard single-storey timber-clad house with no piles needed under the slab, you are looking at around let’s say $160 per m2 mark. If you took that same building and added edge insulation, brick veneer rebates, and additional slab thickness to accommodate in-floor heating - you could be looking at up to $170 - $200 per m2, by the way this excludes the cost of the in-floor heating installation, which varies from $100-150 per m2 depending on the system used.

5 major costs you’ll also need to pay

1. Earthworks and Piles

The most underrated and risky expense of the concrete foundation process is the cost to prepare the ground ready for the slab. This will include both earthworks and pile driving (timber and concrete piles)  - these must be done before the slab can be set out, boxed up and poured. 

It is the foundation of the foundation and must be done right. 

The Earthworks contractors will excavate and remove topsoil and any organic material. They'll level your site, then add and compact a small layer of gravel. Finally, it will be finished with a 25mm layer of sand, this ensures that the waterproofing polythene layer sitting directly under the slab cannot be punctured by sharp rocks.

But there’s more! Depending on the ground conditions, it could also include the construction of a Gravel Raft ( See ‘What is a gravel raft?’), concrete in situ piles or timber driven piles (see different types of piles article).

Factors that will effect the cost of the earthworks on your residential or commercial build:

  1. Depth of topsoil / organic material to be removed - the deeper the topsoil, the more we have to remove from the site and the more we have to bring in to fill the hole back in.
  2. The specific floor level of the slab on the plans - if a floor level is specified by the council and the current ground level is significantly lower, we will need to import more gravel than standard.
  3. An unlevel site - this requires parts of the site to be cut lower, and other parts to be built up. Difficult to estimate until on-site.
  4. Depth to “Good Ground” - if the hard ground is found lower than anticipated, it may increase the export volumes.
  5. Geotechnical engineer's recommendations - These can vary greatly depending on which engineer is handling the job.
  6. Distance from tip site or quarry - if the round trip to the tip or quarry is greater than 1-1.5 hours, this will increase the cost significantly.
  7. Access to the section - if access is limited to smaller plant or trucks it will increase the time to complete and the cost.

Naturally some projects will require more site prep than others, which will affect the cost. Below are the typical site costs for the following examples:

Example #1 - Flat site with timber piles specified by the engineer - In NZ, this is the most common situation.

150mm of Topsoil removed and replaced with 100mm of AP40 - $45 - $60 per m2

150 SED Timber Drive piles to 4.2m depth - $60 per m2

Blinding Sand Supply and level - $15 - $20 per m2

Total - $120 - $140 per m2

Example #2 - Flat site with concrete piles specified by the engineer.

150mm of Topsoil removed and replaced with 100mm of AP40 - $45 - $60 per m2

Concrete Augured Piles to Depth of 4.2m - $115 per m2

Blinding Sand Supply and level - $15 - $20 per m2

Total - $175 - $195

Example #3  - Flat site with a 1m deep gravel raft specified by the engineer - this is for the special sites where the good ground can not be found at a depth that a timber pile can reach. Canterbury = very common. The rest of the country = uncommon.

Gravel Raft - $300 - $400 per m2 of slab

Blinding Sand - $15 -  $20 per m2

Total - $320 - $420 per m2 

Feeling overwhelmed? We created a simple guidebook that’ll provide you with helpful insights in preparing your building site. The specific costs and benefits of the above options and how to get the most economical and fit-for-purpose result from your engineer.

2. Engineered design 

If you get a foundation designed where the constructability has not been thought out by the designer, you run the risk of major project delays, and your project may become susceptible to material shortage and additional unexpected and unnecessary costs. There are many variables to the foundation, and because things like building codes and MBIE guidelines are often changing - we cannot expect all engineers to know the cost and time impacts of the calculations as they too, change. 

What does that mean for your project? Well, it can mean that there are cheaper and easier ways to do your foundation than what is designed (while still meeting both the building code and MBIE guidelines; however, your engineer may not have thought about them.

How much extra can an overspecified design cost you? 

Well, we have seen many instances where the foundation designed by the well-meaning engineer was up to 2-4 times more than a standard Pod floor. Many times, we have also been able to rethink the design of the foundation along with the original design engineer for some amazing cost-saving results. Long story short - after the earthworks, the design could end up being your biggest cost. So if you are serious about controlling the cost of your foundation, engage with your specialist slab contractor as early as possible. 

The cheapest way to build a slab is to work with a slab contractor who can also facilitate the design on your behalf - they are the experts and can go to bat for you. At Tidy Slabs, we offer this very service - click here

3. Council delays

By not dotting your I’s and crossing your T’s at the design stage (and when submitting your plans for building consent), you run the risk of delays when the council requests more information (RFI).  Key details that may be fishhooks for your application…

  • Correct Geotechnical report.
  • Correct testing completed (CPT, Test Pits, Penetrometer) - MBIE guidelines dictate which areas require which test and which reports, but if you aren’t aware of what you need - it could be a time vampire.
  • Identifying services and load of piles, etc - if your plans don’t accurately show where the existing services are on-site and how your foundation is designed to accommodate them (not all sites will need this) - the council will start asking questions.
  • Correct PS1 documentation and insurance - if you have not submitted a fully compliant certificate from your design engineer (PS1)  then you will have an RFI coming your way
  • Identifying the correct ground conditions - if your design engineer has not correctly identified the ground conditions, then the foundation will not be designed correctly, and the council will send it back.

So what does that all mean?

The councils aim for a 21-day turnaround for building consent applications, but they often leave it up to the final days to submit their RFI’s back to the builder - this “stops their clock” so to speak. If you give them reasons to stop the clock, they will take it.

An unexpected delay from the council at the start of your project could mean you lose the “window” with your key sub-trades (Slab contractor, Plumber, Earthworks). The result of losing this window could add months of delays to your project and additional work rescheduling every other trade that follows. If you get your details right up front, you can avoid the rescheduling - if you don’t you're running the risk of delays. What is the cost? - months of additional holding costs.

4. A foundation that is delivered late

Potentially the largest cost (and often overlooked) for the slab may  well be the late delivery of the slab. Here’s a sad industry fact - 50% of all construction tasks are planned more than once - what is the impact of this on your business?

  • A slab not delivered on the date specified requires rebooking delivery of frames, roof, windows etc. The cost of admin and missed timeframes from sub-trades is substantial.
  • What are the holding costs and opportunity costs for dealing with delays?
  • An disorganised contractorl can really set your project up for failure.

5. A foundation that is not correct

  • A slab in the wrong position, wrong rotation, on the wrong site, or with the wrong dimensions,  incorrect concrete strength or steel is even worse than a delay.
  • The result could be at the worst, pulling the house down and starting again, or at the best delays in schedule while remedial work is completed.
  • Your contractor needs to have a reputable supply chain, robust QA processes and a credible reputation in the market - ie they will be here tomorrow.
  • The long-term cost for your project, business and reputation are in the hands of your subcontractors.

A residential concrete foundation cost breakdown

Example of Concrete Slab Components

Now, we’ve got the earthworks out of the way. It’s time to take a closer look at the actual concrete foundations. I hope you’re starting to get a good idea of why it’s hard to give one magic number when you ask for concrete slab pricing. What goes into a concrete slab? Here’s a  rough percentage breakdown of what goes into a concrete foundation:

Polystyrene / Plastic Pods: 10%

  • This will fluctuate based on the specified depth of the slab. An engineer may require either a 220mm pod or a 300mm pod.
  • Further polystyrene insulation may also be specified depending on the R-value requirement. (Hint: The higher the R-Value requirement, the larger the cost)
  • Sometimes it will make more sense to go for a plastic pod system instead of a polystyrene pod system. What are these? (link to article)

Reinforcing bar and Mesh: 15%

  • It will fluctuate depending on the steel and mesh specified by the engineer. Two-story houses with more load-bearing walls may require more.
  • Standard allowance of H12 straight bar reinforcing and Se62 Mesh

Concrete supply, pump and place: 50%

  • Concrete supply costs - $220 - $280 per m3*
  • Concrete pumping costs - $25 - $35 per m3*
  • Concrete placing costs - $8 - $12 per m2*
  • *All fluctuates depending on locations, concrete strength and finish of the slab required.
  • The volume of concrete, and hence, pumping costs will fluctuate depending on the depth of the slab specified by the engineer.

Labour to construct: 20%

  • Variable depending on the detail in the formwork and reinforcing steel, ie are there stirrups and starters required in the slab?
  • Additional labour allowances will be made for piles, rebates, and additional layers of mesh or stirrups.

Formwork and miscellaneous materials: 3%

  • Will fluctuate depending on the depth of slab and formwork and bracing required. A standard Pod floor requires a 305mm LVL formwork which is the most economical. However, a 500mm deep slab will require additional formwork and bracing.

Project Management and Quality Assurance: 2%

It’s important to note that the above percentages will vary based on a variety of factors. Regardless, it’s a great starting point so you have an understanding of what costs make up the slab price.

Concrete Slab prices - ballpark figures

To help you better understand where the price break comes from, here's a cheat sheet to get started for “Good Ground” conditions and no liquifaction risk.

  • If your overall square metre is 100m2  or less your price per square metre would be $200 - $300
  • If your overall square metre is 100m2 - 150m2 your price per square metre would be $175 - $200
  • If your overall square metre is 150m2 to 200m2 your price per square metre would be $155 - $175
  • If your overall square metre is over 200m2 your price per square metre would be $155

Once you get to this square metre range, your price will highly depend on your building features.

Please keep in mind that these are ranges based on current commodity market prices. These are not permanent prices and will fluctuate with the markets. 

Remember, cheaper isn’t always better.

Although the initial cost may seem intimidating, it doesn’t mean that you should purchase the gear you need from Mitre10 and give it a go yourself. Our first instinct is to compare prices and go with the cheapest option. From peanut butter to laundry detergent to cheese to cars, we’re all guilty of this practice. Save your thriftiness for another time - perhaps a cliche, but a very true one - this is the foundation, a lot hinges on this and you need it to be right. But just as important, this is the start of your project and you can either kick it off to schedule or you could have significant delays. Hiring a professional foundation contractor will generally ensure that all the I’s are dotted, T’s crossed and the slab is finished on time ready for the next trade. 

The old adage, “you get what you pay for” makes sense here. At first, a cheap concrete foundation sounds great. Realistically speaking, it’s a lower-quality product that may take longer and result in more work. In the long run, cheap construction will cost your bank account more. 

Besides, a concrete foundation is an investment - more than that it is literally the foundation for your entire build. The more time and money you invest in a project, the more value it will add — just food for thought.

So, how do I get the cheapest concrete slabs? 

  1. Commission a Geotechnical report that will meet the requirements of the Building Consent Authority that the slab will be built in.
  2. Work with your designer/architect AND your slab contractor to interpret the Geotechnical results before doing any groundwork or getting the slab designed - you never know. Your initial assumption of what works best may be wrong - there are many ways to skin a cat. Quite often this is skipped. 
  3. Request that your designer use the calculation method for H1 If you don’t have in-floor heating in your slab, request that your designer use the Calculation Method in designing your H1 slab insulation - there is a high chance you won’t need to add any additional insulation.
  4. Is your ground 100-150kpa? If the ground is 100-150kpa, you don’t necessarily need piles or significant earthworks - there are options out there - Talk to us to learn more. 0800 83 75 22
  5. Engage a specialist slab contractor who can complete and deliver the full package design and build for you as early as possible - this may save you the most amount of money on your slab, and if you build high volumes of homes - this could save you even more for years to come.

Are You Ready to Build Your Concrete Foundation?

Tidy Slabs planning saves you time and money

If you’re still following along, we hope you can see the array of factors that will influence your total project cost. No black-and-white number we’ve given you will work for everyone. 

Ultimately, the price comes down to:

  • how your ground conditions are
  • how you design your foundation
  • who executes it. 

We’re more than happy to be engaged early on your project and get you a reliable estimate at no cost.

Ready to take the next step in the building process? Give me or one of the Tidy Slabs team a call at 0800 83 75 22 or email to help get you your concrete foundation estimate.

I'll give you a rough ballpark quote; no obligation.

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