Hi All,

We are in the final design stages of our plans before consent and there is one thing that I am unsure about. We are building on TC2 (chch requirement) land so we will be using a rib raft foundation. The main living areas of the house will have a polished concrete floor and for heating, we have opted for a Hydronic underfloor heating system. To maximize the thermal efficiency we will be insulated the edges of the slab. We have only just been made aware of the fact that when doing this you would normally use 140mm framing? I am assuming this will add cost to the build which we have not made allowances for. Our builder has suggested that we just increase the wall cavity and keep the 90mm framing but lay the bricks on the edge of the slab. Are there any potential issues with increasing the space behind the brick and frame? My main concern is rodents getting in there. HAs anyone had an experience with this or have any advice? Regards

Further to my question above. Will the added wall thickness with a standard 90mm frame mean that windows will be inset? Will windows just have a larger sill?

Hi ZachB,

Firstly, before you look into workarounds - check out our site Sponsor Maxraft. They are South Island based, cater for TC2, offer fully insulated slabs and will have lots of detail for you on their website.

You are correct to think about the impact on window positions, which can have annoying knock on effects, particularly around compliance etc.

https://www.ecobob.co.nz/info-and-news/building-design-construction-and-renovations/maxraft---new-zealand-s-only-fully-insulated-concrete-slab/