1. Home
  2.  / Shining The Spotlight On Building Materials

Shining The Spotlight On Building Materials

The key contributor to the value of property investment comes from the quality of construction materials and methodology, writes Anthony Corin.

By: Anthony Corin

30 November 2022


When buying your next investment property, how important is it for you to know how it is constructed?

The key contributor to the value of property investment comes from the quality of construction materials and construction methodology. There are several construction method options presently used in the New Zealand construction industry; timber frame, steel frame, concrete block and poured-in-place concrete being the most common, plus some other minor use methods. There is one that has been used in New Zealand that has proven its excellence overseas. This method is insulated concrete formwork, commonly known as ICF.


TIMBER The most common residential construction method used in New Zealand, past and present, is timber construction. This started from when we built houses in the late 19th century as readily available forests were ripe for harvesting. Typical natives used were kauri, rimu, totara and matai. This lead to the first radiata pine plantations from 1920s and 1930s once those native sources were depleted.

As timber can decay when wet, an early treatment was used to prevent this. This treatment involved painting timber with Creosote; a preservative made from coal tar. This was used up until around 1940 when it was replaced with tanalising, which is a pressure treatment system with water using copper, chrome and arsenic (CCA).

This would appear to be an effective and simple solution to stop timber rotting; treat the timber with toxins so the rot-causing bacteria cannot survive. But how good is this for our health? CAA is either banned or has restrictions placed on its use in the United States, Canada, France, Spain, Italy, Germany, the United Kingdom, Ireland, Japan, Indonesia, Vietnam and Australia.

CCA has pesticide and anti-fungal properties and New Zealand is one of the world’s biggest users of CCA treated timber products.

STEEL FRAME Recently galvanised steel framing has gained popularity and has the same dimensions as timber but is two-thirds lighter and does not require tanalising. Steel-framed houses have much straighter walls but still require water egress protection to prevent eventual rusting.

CONCRETE BLOCK Concrete blocks are pre-formed with thin walls and a space in the centre for reinforcing steel to be placed then filled with concrete. They are made to standard sizes and joined with a 10cm-thick cement mortar. As the blocks are porous they need coating regularly to prevent moisture egress as this could cause the reinforcing steel to rust. Concrete block houses are very solid, however, and have a higher fire rating than timber builds.

POURED-IN-PLACE CONCRETE Stronger again are houses made from poured-in-place steel reinforced concrete. Typical formwork used (to pour concrete inside of) is plywood; metal and plastic are also used. These builds require an additional internal timber or steel frame for housing the insulation and services as well as plasterboard substrate. However, ICF construction does not require this additional internal framing.

INSULATED CONCRETE FORMWORK Insulated Concrete Formwork is an advanced and innovative building technology that meets New Zealand Building Standards and exceeds minimums required by code. ICFs are hollow lightweight insulated forms that are erected at the construction site, and are typically filled with 150mm of
reinforced concrete.

ICFs provide the benefits that have made concrete the material of choice for home building worldwide. ICFs provide two built-in layers of foam insulation which in turn offers over twice the council insulation requirement. This gives an ICF building some sizable advantages over traditional building methods: fire resistance, earthquake resistance, longevity, greater energy efficiency with up to 70 per cent energy savings, temperature control throughout seasons, and increased soundproofing.


For my choice, I only use ICF construction and fill it with waterproof concrete for additional longevity and future liability. The benefits of ICF when compared to alternative construction materials make it an innovative solution for New Zealand construction.

Related Articles