The construction cost could go higher depending on the complexity of the design and materials used on the project, which will occupy a stretch of Tindalls Beach on the Whangaparaoa Peninsula.
The land cost many millions more. The residence will be on a 2435 sq m site, marked by the dotted line on the image above, made up of three sections recently cleared of $7.7 million worth of dwellings by barge and road.
They were a four-bedroom house built in 1992 (bought for $2.5 million in 2008), a five-bedroom 1970s house (bought for $2.9 million in 2004) and a three-bedroom house built in 1957 (bought for $2.3 million in 2012).
When the Herald visited the site this week, there was bare clay where the three houses once stood.
The section was fenced off with makeshift wire fencing and minor earthworks had begun, with shallow holes and black plastic visible.
Good Brothers Group, a west Auckland company, is building the property for the 52-year-old, who led Oracle Team USA to an America's Cup win over Team New Zealand last year. A representative of the firm did not return calls.
Sumich Chaplin Architects also declined to comment, saying its projects were subject to confidentiality agreements.
Sir Russell's personal assistant said her boss did not give interviews on his personal affairs.
The Olympic sailor, who was knighted in 2009 for his services to the sport, owns other properties around the country, including a Takapuna apartment and homes and land in Central Otago.
An Auckland Council spokesman said consent was granted last year to clear the sites.
There were no objections.