An extensive $5.5 million upgrade of Ōrewa Library will begin on Monday, aiming to address increased visitor numbers and maintenance needs.

The project, set to be completed by June next year, includes deconstructing two-thirds of the current library and adding a mezzanine floor.

Hibiscus and Bays Local Board Deputy Chair Gary Brown highlighted the necessity of the upgrade.

"The library is a popular hub for our community, and this upgrade is essential," Brown said.

Visitor numbers have topped 235,000 annually, prompting the need for more space and improved facilities.

The upgrade will see the existing footprint reconfigured, a new mono-pitch roof, and various interior enhancements to create a more open and accessible environment.

During the 15-month renovation period, a temporary mini-library will open at the Ōrewa Community Centre on July 8.

Rachael Rivera, Head of Community Delivery, assured that services would continue with minimal disruption.

"Staff will be on hand to help people access the services available at the mini-library," Rivera said.

"Ultimately, this extensive upgrade will transform our library and enhance the space."