The Building Diaries: Part 3: The Foundations :


Build me. Editor Hana Deavoll and family are building their own home in Queenstown. Follow the journey as they buy land, plan their dream home and oversee the building process. The Deavoll Family includes Hana (37), builder Sam (36), and their children Indy (7), Phoenix (4), and Sonny (2).



With our plans confirmed and building consent granted it was finally time to begin building our home. Our section is relatively flat, but even so a 250mm difference in height across the section meant a few days of earthworks to strip off the excess dirt, as well as the green matter that needed removing anyway. Once the site was stripped and flattened, then a layer of gravel was brought in and compacted flat, the house could be set out and the slab installed.


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 Photo: Sam getting stuck in with the digger


Slab Design

We are installing a MAXraft slab for our foundation. MAXraft is a fully insulated raft system which offers superior heat retaining properties for the home. A raft system is a slab that 'floats' on the surface. A MAXraft slab is engineered and prefabricated specifically for your home. In layman's terms, it is like a giant jigsaw puzzle of polystyrene, with bowl-like edges that hold the concrete within. The polystyrene acts as a thermal break, stopping any heat loss from your home out through your slab.

Benefits of a MAXraft slab include:

- R Value of 4.5 

- Faster installation time due to prefabrication of poly and limited boxing

- Full insulation with no breaks, including the entire perimeter and base of your slab.

- A warmer, more efficient home, meaning lower heating costs, and 40% more effective underfloor heating


The extra few thousand we are spending on the insulated slab will be made back within the first few years due to power savings.


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Photo: Close up of MAXraft insulation, photo by MAXraft 


Slab Installation

After the gravel was compacted and the house footprint set out with profiles, our plumber Daryn from Well Connected came and dug it all back up again in order to install the pipes for water and gas. A conduit to the island bench was also put in for electricity by RLS Electrical. The building crew then re-compacted the gravel around the services ready for the slab.

With a raft slab system, we started our foundation with a layer of polythene (black plastic) that sits on top of the compacted gravel. The builders made sure to tape up all the services (plumbing pipes etc) coming through to stop moisture coming into slab. They then put perimeter boxing up ready to enclose the MAXraft insulation.

Our MAXraft 'jigsaw puzzle' arrived as pre-cut sheets of polystyrene which fitted perfectly into our perimeter boxing, covering the entire building footprint. The MAXraft guys installed the insulation, which was later covered with engineered steel and mesh by our building crew (the photo below shows it covered in heavy items so that it doesn't blow away!)


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We also installed water pipes for the underfloor heating system we will be using, which will be heated by an air to water heat pump.


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Finally the builders could take a rest as we handed it over to the concrete crew to pour the concrete, this involved Allied supplying the concrete, AAA Concrete Pumping Services the concrete pump and J. Ashby Concrete expertly placing the concrete. The concrete pour is always exciting as it marks the overcoming of a huge hurdle to get to that point; the section, design, building consent, earthworks and slab prep. Myself and my two youngest boys went along and watched the mixer trucks as our new house foundations started to take shape.


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watching concrete truck, foundations, build me, building nz


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The concrete crew started at 9am, but unfortunately, later that afternoon the rain arrived and our slab started to suffer, luckily it didn't get too heavy so the placers floated it back smooth again. Overnight our newborn slab faced more problems with freezing temperatures. This resulted in some slight imperfections on the surface, but luckily not too much of an issue as our flooring (carpet and wood) will cover all the concrete. If we had been going with exposed concrete we would have had to hold off pouring the concrete for a few days, or risked a less than quality finish.


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Photo: The finished slab. The metal fixings are for the triboard walls. The boxing will be removed from the edges as soon as the concrete is set. You can see where all the bathrooms, sinks and toilets are as that is where the services are poking through.


Our Finished Foundation 

With the slab poured and set, we took the opportunity to stroll around our new home and get a feel for the size. This is the 3rd home we have built for ourselves, and I think this time we have the size just right. Our first house was an 80m2, 2 bedroom flat, a perfect size for a small family. We upgraded a few years later to a massive 250m2 4 bed house and felt it was too big, children were getting lost in there! So a year later we were back in the original 2 bed property, renting it from the new owners. But now we have finally outgrown that, and will appreciate the extra space that this new foundation will give us.


Next week - our prefabricated triboard walls and ceilings will arrive and the build will continue.




- A fully insulated slab is a great investment, especially if you are using underfloor heating.

- You need to decide on all floor coverings before your slab is installed.

- If you are having exposed concrete floors you need good weather conditions for the pour


Related Articles

The Building Diaries: Part 1, The Section 

The Building Diaries: Part 2, Design & Planning

The Building Diaries: Part 4, Framing & Trusses

The Building Diaries: Part 5, Roofing

How to Build a House

Free EBook - Building in NZ: An Essential Guide to Building Your Own Home