Portuguese studio Aires Mateus has transformed a house in Portugal into a bright white building with a sprawling extension (+ slideshow).

The three-storey house is located in Alcobaça, a Portuguese city dominated by the presence of a twelfth century monastery, and it occupies a large irregularly shaped site on the edge of the river Dull.

Aires Mateus upgraded and extended an existing residence and made every surface inside and outside of the house white, allowing it stand out amongst the brown and pink tones of the surrounding local architecture.

The new windows appear as narrow vertical slices. Some of them overlap the white-painted frames that housed the windows before the renovation and each one is sunken into a deep recess, revealing the thickness of the exterior walls.

Residents enter the house on the middle floor, where a staircase leads up and down towards either a top floor mezzanine or a lower floor living room.

A curved skylight punctures the roof overhead and projects a teardrop-shaped splash of light onto the walls of the stairwell.

Another curved opening leads from the living room to the rooms of the expansive extension, where a kitchen, a dining room and three bedrooms are spaced out around a series of small square courtyards.

Storage closets are contained inside each of the thick walls that separate the rooms.

The L-shaped garden wraps around the edge of the house and is bounded by the chunky white perimeter walls.

Aires Mateus is a Lisbon-based architectural studio led by Manual and Francisco Aires Mateus. Past projects include a nursing home in Alcácer do Sal and houses with sandy floors that were exhibited for the Venice Architecture Biennale 2010.

See more Portuguese houses on Dezeen, including a house in Lisbon with bushy plants on its facade.

See more architecture in Portugal »

Photography is by Fernando Guerra.

Above: lower ground floor plan - click above for larger image

Above: upper ground floor plan - click above for larger image

Above: top floor plan - click above for larger image

Above: cross section - click above for larger image

Above: long section - click above for larger image

Above: rear elevation - click above for larger image