The single-storey extension named Shadow House provides new living spaces, a guest bedroom and garage for the house, which is located a conservation area in Melbourne's Elsternwick neighbourhood.
A 1980s extension was cleared away to make room for the addition, which takes its design cues from the early 20th-century villas surrounding it.
While Gibson borrowed some features from these historic houses – including the steep hipped roof – he also used dark zinc cladding to deliberately distinguish it from the brickwork of the existing property.
"The zinc clad structure is seen as a recessive folded form from the street, set back, subordinate and essentially in the shadow of the Edwardian brick structure," explained the architect.
"Rather than replicating and competing with the character of the original house the new works are clearly distinguishable allowing the heritage fabric to take on greater clarity," he added.
"In the context of this neighbourhood, the design challenges the concept of building low-quality replica additions that attach themselves to heritage fabric and, in effect, compromise, confuse and diminish the integrity of the original."
The extension wraps two sides of the original house. Areas of red brickwork are left exposed inside the living spaces.
Large windows and folding glazing on the other side of the extension frame views out into the garden.
"The new works analyse, interpret and enter into the spirit of the heritage building," said Gibson.
"And utilising technologies of our time provide a simplified interpretation that is both contemporary and yet interactive, and respectful of its environment whilst embracing the very tenants of Edwardian virtues – villa within a garden setting."
The white faceted ceiling follows the form of the hipped roof. In the kitchen, wooden cabinetry fills the space between the floor and ceiling.
Gibson likens the irregular form to a piece of crumpled paper.
Tall deciduous trees and a vine-covered wall help to shade the extension on the western side.
This is part of the property's passive energy system, which also includes insulating wall cavities, double and triple glazing and rainwater harvesting.
Gibson, who won an Australian Institute of Architects' Award for Residential Alterations and Additions for the project, has completed several other extensions in the city – all of which make an effort to be distinct from the original buildings.
"Diverse cities must balance greater density with the ability to cater for a variety of housing types which includes maintaining heritage," he said.
Architecture: Matt Gibson Architecture + Design
Project team: Matt Gibson, Weian Lim, Cassie Southon, Erica Tsuda, Angela Hopkins, Phil Burns, Josh Cousins
Interior design: Matt Gibson Architecture + Design with Mim Design
Interior decoration: Mim Design
Landscape design: Ben Scott Garden Design
Builder: Warwick Constructions