WHS board of trustees property committee chairman Wayne Foley said the new block would cost more than 80% of the $2.25 million of construction and improvement taking place at the school this year.
Expected to be completed by the end of November, the block will be built off the side of the school's Robertson Block.
It will offer 249sq m of basement-level space and 457sq m of ground-floor room.
The basement will include four practice rooms, band and seminar rooms, and a costume and props room, and will be "acoustically rated" and wired for a recording studio.
Upstairs, there will be two music rooms, two drama rooms, two "green room" changing areas in the middle with a stage at either end, and an additional loft learning space created between the new building and Robertson Block.
"Those will represent more than doubling of learning areas for music and drama," Mr Foley said.
"Also, there will be big sliders so they will be able to open up the doors on to the courtyard to have concerts here."
He wanted to acknowledge the "fantastic contribution" teacher Alison Price had on music and drama in the school and was happy at the opportunities the development would create.
"We know how talented our local school kids are in music and drama and to be able to provide them with these facilities is great."
The school's new canteen was completed two weeks ago, and the previous canteen in the school hall has been demolished to make way for two new classrooms, alongside refurbishment of the existing changing rooms by the end of August.
"Originally there was a 10-year development plan by Opus for the school and we are following the initial part of that ... Once we have this project under way we will do a review of what other building works we would like to undertake in 2012." These would probably include a new library, he said.
The new canteen, with its 28sq m of covered queueing area, would open up opportunities to cater for community activities, he said.
The construction is being carried out by Amalgamated Building Ltd, with funding coming from budgets agreed on between the school's board of trustees and the Ministry of Education.
Diggers are expected to arrive today to undertake the first earthworks on the block.
