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Spectacular cantilevered concrete roof

Lovers of concrete, Jack McKinney (Jack McKinney Architects), designer Rachael Newnham and partner and builder Cameron Ireland (a craftsman of anything concrete), have conspired and collaborated to produce a truly jaw dropping home for Cameron, Rachael and their three children … an effort that won Home of the Year in 2019. 

“The concept for the house started many years ago when we spotted a diagonal, cantilevered concrete roof in a 1960s book on architecture and it started us thinking we could do something like that for our own home on a site in Grey Lynn,” says Cam. “I took the idea to Jack and it evolved from there.” 


Newnham, Ireland, and McKinney have worked on about 20 projects together over a number of years. “I don't think I would have even attempted a project with the complexity of this one if Cam wasn't the builder as he has an amazing skill set. He, like me, loves concrete and what we can do with it,” says Jack.  

The house is a strongly sculptural exploration of in-situ concrete. A basement garage forms a podium upon which a 54 tonne diagrid concrete roof is propped up to create a living, kitchen and dining area. The main living space is open to the East and the North. The project also explores a range of materials in their raw state, deliberately contrasting areas of brightness with darkness.

“It turned out to be quite an incredible experience,” says Cam. “The engineer, when he saw what we wanted to do, thought we were crazy. There is 54-tonne of cantilevered concrete roof up there. We certainly pushed the boundaries on this one.” 
 
"We've done well over the years to push things quite far," says McKinney of the various houses and alterations, many of which have been in heritage zones. "But there was a bit of pent-up frustration to do something unrestrained on both sides. Just to do something fun. Because Cam was the builder and client, it allowed more experimentation than you ever could within a normal client, architect and builder relationship." 

"Where does my love of concrete come from?” says Cam. “About 20 years ago everyone was using blocks for everything. I thought that there’s got to be a better way. I found a shutter system for board-form concrete which allowed me to create different shapes and forms out of solid concrete. It's a lot stronger than block work and far more watertight. I’d far rather use board form concrete than block walls in construction. And, concrete lasts forever.” 

Cam talks about how he managed to construct the unusual roofline. “Firstly we completed the board-form walls which would eventually carry the weight of the roof,” says Cam.  “We then built a false floor on top to carry the weight of the boxing and concrete for the structural length-wise beams. Before we removed the boxing I allowed the concrete to cure for about six weeks before we could create the diagonals. Then we removed the false floor and we had our roof.” 
 
To ensure the watertightness of the concrete Cam requested a waterproofing additive in the mix from Firth, his concrete supplier. “Firth do a good job for me. I tell them what I need and I get it.”  
 
Cam says that he also incorporated lighting into the concrete beams instead of hanging light fixtures. Glass panels fill the gaps, completing the structure. 
 
“You can do pretty much anything with concrete and the texture is quite raw which works well with glass,” adds Cam. “It also creates a contrast and makes any artwork standout. For me it’s just the medium I love to work with.”  

Customers: Rachael Newman and Cameron Ireland  
Architect: Jack McKinney Architects 
Builder: Cameron Ireland Builders 
Products: Firth Structural and self-compacting concrete 
 
View a video of the diagrid house here.