Pumice house built to last

Alan Bakker (left) and Rob Reid. Picture / Alan Gibson

Their house will withstand earthquakes and hurricanes - and it's made of pumice.

Compressed pumice blocks, to be accurate.

Developers Rob Reid and Alan Bakker say the 180sq m house in Kawerau is also environmentally friendly, durable, warm in winter and cool in summer, fire-resistant, soundproof, rodent and insect-proof, handsome and affordable.

"This house breathes so, basically, it's a living unit," Mr Reid, a builder for more than 30 years, says of the prototype, which will be finished in a few weeks. "It will never fall to bits. I can't think why everyone wouldn't want one."

He says he can't wait to live in a pumice home himself.

Like some other parts of New Zealand, the Bay of Plenty has generous resources of the natural, volcanically formed material, which is a lightweight silica honeycombed with air pockets.

A great insulator, pumice is ideal for compressing. It needs no processing, is non-toxic and moisture won't erode it.

Earlier attempts to build with pumice in New Zealand "never really took off", says Mr Reid.

The lightweight blocks, bonded with a cement slurry, are 10 times stronger than the earth building code requirement, says Mr Bakker, who has a pumice quarry at nearby Awakeri.

The two men have spent years perfecting the block technique and use a heavy industrial machine originally designed to make earth bricks which produces 500 blocks an hour. The Kawerau house and retaining walls have taken 8000 high-quality pumice blocks.

When covered by a special plaster into which a silica-based paint is etched, they have a slight adobe finish.

The pair chose Kawerau to showcase their three-bedroom pumice house because it is more affordable than neighbouring towns and cities for first-home owners and the retired. The house - expected to sell for upward of $250,000 - has also been designed to be user-friendly for disabled people, with its wide doorways and passages and easy indoor-outdoor flow.

Despite the advantage of a much greater wall thickness, the pumice house is comparable to conventional timber-frame construction in its basic $1100 to $1200 a square metre cost.

Pumice Developments (a second company, Pumice Products, makes the blocks) already has orders for three houses in Whakatane and two in Whitianga.

VERSATILE PUMICE

* Used as fill in road construction, as sand in concrete block manufacture, and for foundations and drainage.

* Horticulturists use it as a soil additive, and it is a growing medium for hydroponics plants.

* As an exfoliant in beauty treatments.

* To stone-wash denim jeans.