The playground slide, tree house and tunnel that won at the 2018 NZ Architecture Awards

A playground slide, a tree house and a tunnel have all been awarded the highest honours at the 2018 New Zealand Architecture Awards.

The awards ceremony, which was held by the New Zealand Institute of Architects in Wellington on Friday, honoured an innovative and fun roof top slide at Cathedral Grammar School in Christchurch.

"There's this incredibly rigorous building which has then been occupied by all these gorgeous children, and they've just adorned the place with all their cool kiddy art, and the contrast is fabulous. It is a very serious piece of architecture," said one of the judges.

Other winners included Auckland's controversial $1.4 billion Waterview Tunnel, which was designed to both ease congestion and bind communities together.

"From an international basis, they are starting to do this more, but for New Zealand its fresh eyes and a fresh case," said its architect.

The jewel in New Zealand's housing crown was a Piha beach bach - a three bedroom tree house sitting in a pohutukawa forest.

"Sometimes I see it more as a bird cage, with people living in the cage and the birds flying around," said its architect.