Funds for the build had been saved from Ministry of Education allotments for five years, along with the latest allocation and a small "top up" to enable continual building without interruption.
"We've been very patient," Mr Hensman said.
"The beauty of this plan is the build comes first, demolition second - the space is between existing buildings so there will be no disruption to learning. It's a really clever design thanks to Garry Pidd Architects."
Work will bring Taradale's science sector into one area, as it is currently spread across three different blocks - something Mr Hensman believed would benefit both students and teachers.
Interior glass walls allowed pupils to learn what was happening in other classes and observe varied teaching methods, while large sliding doors between rooms could be pushed back to create large combined classes.
Each room was equipped for practical science, with a cluster of four specialised science labs at the heart of the building providing a haven for the subject to blossom.
"We're creating a building that is significantly more flexible than any science facility we've seen in other centres," Mr Hensman said.
Based on the ground-breaking ideas of Prakash Harvard of Harvard University, the new design will encourage greater collaboration between teachers and increase opportunities for practical science.
Next year science staff will have their say in how to make the best of a new learning environment.
The school's Board of Trustees' were right behind positive change with modern facilities proving a boost for the school.
"Unfortunately, in the last few years we have been hamstrung for our share of government funding, due to priorities with the Christchurch earthquake and leaky buildings within other schools," Board of Trustees' chairman Tim Smith said.
"As a result of being fiscally responsible over the last eight years the school has managed to improve its finances and build a property fund."
The new 1017sq m block will have the latest in wireless networking to ensure IT and e-learning is world class.
"We are all very excited about what lies ahead for THS, with a modern learning environment for our students that will be top class," Mr Smith added.
Taradale Intermediate classes use existing labs to enhance their own science programmes, meaning they, too, benefit from the fresh space.
It would also host a hub for counselling and career guidance.