Sustainable, striking and … absolutely stunning

“We ‘inherited’ an existing 3-bedroom house sitting on top of a large concrete block basement, with an adjacent garage at the upper level to work with,” explains Dave. “A number of factors impacted the decision to avoid a full demolition of the existing house and basement. The upper level of the house could be moved off and sold; the dumping costs of concrete on the island are very high; and the embodied energy left in the concrete slabs and the 250mm block basement walls could be taken advantage of as part of the addition/alteration.”

Dave explains that the materials chosen for the house had to be durable, requiring little maintenance and needed to suit the coastal environment where salt and wind can be challenging. “Concrete is one of the most durable and flexible materials there is,” says Dave. “We designed the home to take advantage of the views without sacrificing protection and refuge from the elements.”

“Another plus in using the ‘off the board’ concrete feature walls is that textured concrete walls help with acoustics. Any broken surface is better acoustically."

"Plus the heavy texture suggests a rugged, durable material that - although often used on exteriors - has been threaded through into interior spaces as well.”  Soft hues of natural timber have been used throughout the house and kitchen contrasting well with rugged concrete features.

Given the unpredictability of the weather, Dave also needed to create a decked area that could be occupied away from the direction of the wind. Internally the spaces can be opened or closed, depending on what the weather is doing, and feature an impressive off the board concrete hearth and pizza oven.

“Re-using the existing foundation did pose a few challenges, as you’d expect, as it required additional footings and inclusion of the pipes and services) but it did mean in the end we were able to create extra space the client has turned into a sauna and wine cellar,” explains Mark.  “It’s hard to know when you start a renovation what you will find but the client was absolutely on board with the additional work required and from an environmental point of view it was certainly worthwhile.”

Key to the stunning impact of the home are the insitu off the board concrete walls. “This was one of the larger insitu projects we’ve done,” says Mark. “There’s quite a bit involved in getting these walls right. We often check in with Ross Bannan, Concreteologist on projects of this scale. He’s the guru of insitu concrete pours. He ensures the mixes used are suitable for the pour and checks the formwork. It’s worth seeking advice from experts to make sure we get the results we are after.”

“Sometimes these types of walls can have small areas that are pitted, or the pattern doesn’t come through from the timber onto the concrete, which may have been because the cement and aggregate didn’t mix correctly,” says Mark. “It’s knowing what can happen, trying to avoid it and being able to fix it if it does. So it’s not as simple as just pouring concrete into boxing.”

“All the concrete, foundations, features, driveways and paths are Firth supplied,” says Chris Pope, Certified Plant Manager for Waiheke Concrete. “The large feature walls required a Self Compacting Mix as they were poured by the guys on site, and having a pump operator on site who is experienced in this type of concrete work is also important.”

“Chris and the guys at Waiheke Concrete are really accommodating,” adds Mark. “He’s really great actually. It wouldn’t always be easy to keep everyone going on the island as all the aggregate has to be barged over. They do a good job. And Sam Marshall, our concrete pump operator, was excellent too.”

“It's a beautiful home and the design is awesome,” says Mark. “It fits the site so well. The roof structure is amazing and the concrete and ply work well together. We just love it.”

Oneroa House not only embodies the architects’ design approach but the owners’ dreams which have truly been embedded in its foundations. “As architects, we feel really privileged when clients enable us to be part of adding a framework of buildings, and some life, around their dreams,” says Dave.

A wonderful retreat, Oneroa House, is perfect all year round with its panoramic ocean views, while satisfying the owners’ passions for entertaining friends and family with home grown wine and food.

• High levels of insulation beyond code, double glazing, insulated thermal mass and low VOC finishes have been used throughout.
• Water collection, treatment and storage was increased due to very low rainfall over the summer months. An upgraded effluent system treats waste on site and assists with regenerating bush.
• The use of louvres and actuator-driven high-level windows creates a breezeway via the internal planted courtyard, that pre-conditions the air.
• North, south, east and west facades all feature different glazing treatments, roof overhangs, shrouds and plan recesses to deal with differing climatic conditions and orientations.

Architect: Strachan Group Architects (SGA)

Builder: Dawson Construction

Location: Oneroa, Waiheke Island

Product: Certified Concrete® - Insitu Self Compacting Concrete feature wall with Black Oxide

Photography: Simon Devitt