Systems we specify
An uninsulated slab is one of the biggest, hardest-to-fix heat losses in an ordinary Tasman home, so we default to a fully insulated MAXRaft foundation on almost every build. It is on The Green House, The Blue House, Tasman View and The Black House, among others, and pairs with Terra Lana, Mammoth or XPS underfloor insulation on the timber-framed builds where a raft slab is not the right fit for the site.
We choose MAXRaft because it does the most for the least: the polystyrene forms double as permanent insulated formwork, so the slab is warm from the first pour rather than needing extra work later to fix it. On the cold valley floors and clay sites common across Nelson and Tasman, a warm slab keeps floors comfortable underfoot through winter and takes real load off the heating system for the life of the home, whether or not the rest of the build goes all the way to Passive House.
MaxRaft fully insulated slabs are designed specifically to increase the performance of your home from the foundation up: a healthier, more cost-effective home from the very first pour, and one of the most cost-effective performance gains you can make on a new build.
Terra Lana wool-blend underfloor insulation outperforms other underfloor products because of its ability to breathe, a safe, healthy, low-impact choice for a suspended timber floor.
Mammoth Modern Insulation is 100% polyester, much like your duvets and pillows. It is non-itch, non-toxic and made in New Zealand by a carbon-zero certified manufacturer, from recycled fibres including plastic bottles.
XPS is a high-performance rigid foam board insulation with high compressive strength. It is especially useful in under-soffit applications and for cavity walls, roofs and other types of flooring.
On real homes
The Green House, the Blue House, Tasman View and The Black House all stand on a fully insulated MAXRaft slab, a performance win built in before the first wall goes up.
Good questions
An insulated foundation slab wraps the concrete in rigid insulation underneath and around the edge, instead of leaving it to lose heat straight into the ground. It is one of the biggest, cheapest performance wins available on a new build, because you cannot add it later.
Yes. MaxRaft fully insulated raft slabs are one of our standard foundation systems, specified to lift a home's performance from the very first pour rather than trying to catch up later.
Yes, for most sites. A warm slab means warmer floors and a smaller heating load year round, which matters in a region with cool winter nights and a strong case for keeping running costs down over the life of the home.
Yes. Our Green House build in Upper Moutere runs on a MAXRaft slab with ducted heating in the floor, built as part of a continuous insulated envelope to the Passive House standard.
We specify Terra Lana wool-blend or Mammoth polyester underfloor insulation depending on the design, both packed to well above the Building Code minimum so a suspended timber floor performs just as well as a slab.
Talk to us about the insulated foundation system that suits your design and site.
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