A marble-lined steam room is squeezed below the sloping ceiling of this apartment extension in Lisbon by local studio Camarim Arquitectos (+ slideshow).

Camarim Arquitectos remodelled the spaces of what was previously a separate apartment, located above the one that was already occupied by the client.

When the previous owner left, the client purchased it so that he could extend his two-bedroom property.

The upstairs apartment was originally separated into a living room, with a door opening onto a small balcony and a larder situated beneath the sloping ceiling.

The architects, who also recently completed a Lisbon townhouse, were asked to transform the apartment into a self-contained living unit with its own living room and kitchenette so the owner can work and relax away from the main residence below.

To introduce more natural light into the previously gloomy interior, they extended the glass doors connecting the living room with the balcony, removed the wall between the living room and the attic space, and added a skylight to the sloping roof.

A master bedroom, exercise room and the steam room – known as a hammam – are all separated by a variety of translucent curtains, screens and reflective glass surfaces to ensure a continual distribution of light between these spaces.

These materials vary in opacity and reflectivity, depending on the lighting conditions and the layering of the surfaces.

Sliding doors made from reflective glass partially conceal a small kitchen and the entrance to the attic area when closed. They become more transparent when the lights behind are turned on.

A mirrored wall flanking the balcony on one side creates the illusion of more space. Folding glass screens can be used to weatherproof the balcony and an internal curtain can be drawn around the windows for privacy.

The interior's different spaces are further demarcated by the application of various materials, with Vila Viçosa marble in the hammam, teak wood in the bedroom and a synthetic self-levelling floor in the living room.

A corridor leading from the entrance towards the living room incorporates a trapdoor in the floor, which can be lifted up to reveal a staircase that descends to a small reading room in the main apartment below.

The architects also remodelled a second apartment purchased by the client that adjoins his existing home, adding rooms including a marble-lined bathroom separated from a bedroom by a transparent bookcase.

Photography is by Nelson Garrido.