If your new home is going on a concrete raft slab, it is almost certainly a pod floor — a grid of lightweight void formers that the concrete is poured around, leaving stiffening ribs between them. The choice most people never get asked about is what those pods are made of: expanded polystyrene (EPS), or moulded recycled plastic.
Heritage Homes uses QPOD, a New Zealand-made pod manufactured from 100% recycled plastic. Here is what a pod floor actually is, how the two materials differ on site, and why we made that call.
What a pod floor actually is
A raft or waffle slab is built up rather than dug down. The site is levelled, drainage and services are set out, edge boards and a damp-proof membrane go down, and then the pods are laid across the area in a grid with spacers between them. Steel reinforcing goes over the top, and the concrete pour fills the gaps between the pods and covers them.
The concrete that runs between the pods forms a grid of ribs — the “waffle” — and those ribs are what give the floor its stiffness. The result is a strong, stiff slab that uses less concrete than a solid slab of the same overall depth, which is why raft systems are common on sites where ground conditions call for a stiffer floor.
The pods themselves do no structural work once the concrete has cured. They are formwork that stays in place. That is exactly why the material they are made of is a construction and environmental question rather than a structural one.
Polystyrene pods vs recycled plastic pods
| EPS (polystyrene) pods | Recycled plastic pods (QPOD) | |
|---|---|---|
| Material | Moulded expanded polystyrene, roughly 98% air | 100% recycled plastic, moulded and made in New Zealand |
| On-site waste | Cutting releases loose beads that travel on the wind | Offcuts effectively non-existent, and recyclable |
| Stability during the pour | Light; can shift and needs managing in wind | Interlocking, so units stay put during the pour |
| Delivery | Bulky — volume means multiple truck loads | Compact — a house lot fits on a trailer or ute |
| Storage on site | Bulky and vulnerable to wind and damage | Stacks on a pallet — around 50m² of product per pallet |
| End of life for surplus | Difficult to recycle once contaminated on site | Recyclable at New Zealand recycling depots |
| Certification | Systems vary — check the specific product | CodeMark certified |
Product specifications change, so confirm current details with the supplier for your build. The pattern, though, is consistent: the two materials behave very differently between delivery and pour, and identically afterwards.
The polystyrene bead problem
This is the one that decided it for us. Expanded polystyrene is made of fused beads, so the moment a pod is cut or knocked, loose beads appear — and they are light enough to cross a site on a breeze, collect in fence lines, and find their way into stormwater drains and waterways. On a windy site, containing them is a genuine daily task.
Recycled plastic pods do not produce beads. Cutting is largely designed out because the units assemble to standard foundation dimensions, and what surplus there is stays as solid, collectable, recyclable material. For a builder, that is a cleaner site with less chasing; for a neighbourhood, it is the difference between a tidy build and polystyrene in the gutters for a fortnight.
Why Heritage Homes uses QPOD
- No loose beads. The environmental and site-tidiness reason above, and the one clients notice.
- It stays where it is put. The pods interlock, so the grid holds its position through the pour rather than needing constant adjustment — including in wind.
- It stores on site. A house lot arrives on a trailer and stacks on a pallet at roughly 50m² per pallet, instead of consuming a corner of the section and blowing around it.
- Recycled and recyclable. Made in New Zealand from 100% recycled plastic, with surplus recyclable at NZ depots — a genuine circular story rather than a claim on a brochure.
- CodeMark certified. Certification gives the building consent authority assurance of Building Code compliance, which means one less question in an application.
That last point matters more than it sounds. Consent delays are overwhelmingly caused by requests for further information, and every certified, well-documented component is one fewer thing for a council to query — as covered in our guide to getting a new build through council.
What about insulation?
The reasonable objection to swapping polystyrene for plastic is thermal: polystyrene is an insulator, so surely the floor performs worse without it?
In a pod slab, most of the insulating effect comes from the air voids the pods create rather than the pod walls, and plastic pod systems are designed to deliver comparable performance to an EPS waffle slab. It is also worth knowing that pod depth has less influence than people assume — published analysis suggests doubling waffle pod height increases the added insulation value by only around 14%. Because the numbers depend on the specific system and depth, confirm the R-value for your build with the supplier and your designer rather than working from a rule of thumb.
Is a pod floor right for your build?
A raft slab is one option among several. It suits sites where a stiffer floor is wanted, and it pairs well with in-slab underfloor heating because the slab is the thermal mass. It is not the answer on every section — sloping sites often favour a timber floor on piles instead, which also gives you subfloor access and storage. That whole comparison is in concrete slab or timber floor on piles, and the ground conditions that drive the decision are covered in choosing a section for a character home.
Heritage Homes builds character homes on both slab and timber-floor foundations across New Zealand. Where a raft slab is the right answer, we build it with recycled plastic pods.
Frequently asked questions
What is a pod floor or waffle raft slab?
A raft or waffle slab is a concrete floor built on a grid of lightweight void formers — the pods. The pods sit on the ground between edge and internal footings, and concrete is poured around and over them. The concrete that fills the gaps forms stiffening ribs, so you get a strong, stiff floor using less concrete than a solid slab of the same depth. It is a common New Zealand solution on sites where ground conditions call for a stiffer floor.
What is the difference between polystyrene and plastic slab pods?
The material forming the void. Traditional pods are moulded expanded polystyrene (EPS), which is about 98% air and cuts easily on site. Recycled plastic pods are hollow moulded units that clip together to form the same grid. Both create the voids that produce the concrete ribs; they differ in how they behave during construction, how much waste they generate and what happens to offcuts afterwards.
Why do polystyrene beads end up around building sites?
Because of what EPS is. Expanded polystyrene is made of fused beads, so cutting or breaking a pod releases loose beads, and they are light enough to travel on the wind across a site and into drains and waterways. It is the most common environmental criticism of polystyrene pods, and it is a site-management problem for the builder as much as an environmental one.
What is QPOD and why does Heritage Homes prefer it?
QPOD is a New Zealand-made raft foundation pod manufactured from 100% recycled plastic, and it holds a CodeMark certificate. Heritage Homes prefers it for practical reasons as much as environmental ones: the pods interlock so they stay put during the pour, there are effectively no loose beads to escape, offcuts are minimal and recyclable, and they stack compactly enough to store neatly on site.
Do plastic pods insulate as well as polystyrene pods?
In a pod slab, most of the insulating effect comes from the air voids the pods create rather than the pod material itself, and plastic pod systems are designed to deliver comparable thermal performance. Because performance depends on the specific system and pod depth, confirm the R-value for your build with the supplier and your designer rather than assuming a figure.
Does a CodeMark certificate help with building consent?
It helps. CodeMark is a product certification scheme under the Building Act, and a current CodeMark certificate gives building consent authorities assurance that a product meets the Building Code when used as specified. That does not guarantee any consent outcome, but certified products give the council one less thing to query — and queries are what stall consents.
Ask us which floor system suits your site
Prefer to talk? Call Heritage Homes on 0508 40 30 20 or email sales@hhomes.nz.