When interior designer Jason MacLean discovered an original 1970s California-cool modernist house for sale in Camberwell in 2006, he jumped at the chance to buy it. “I came to view the house on the Saturday and bought it on the Monday,” he recalls. “The week before, I had been to Palm Springs. I love the period architecture there and I had visited the Eames House, too. So when I saw this place I fell in love with it.”

Built and once occupied by British architect Martin Crowley in 1979, the single-storey compact house with a flat roof is a classic piece of infill architecture. It’s set on a back street where it is virtually invisible, tucked away between a row of garages. The black-painted front facade is largely blank, save for a bright orange door through which you access a cobbled courtyard. Here, Douglas Deeds white fibreglass pots are dotted around underneath a black I-beam frame that extends out from the steel, glass and brick structure of the house. A bamboo garden helps to screen the towering Georgian terraces behind.

Here comes the sun: bold colours and pattern in the kitchen. Photograph: Edmund Sumner/The Observer

“It’s so private here, no one really knows the house exists,” says MacLean, who now shares the live-work space with his wife Jenny Rose – with whom he opened the design agency Studio MacLean in 2013 – and their six-year-old son, Stanley.

Inside, the layout is built to a modular plan with three bedrooms (one of which has been converted into a studio), an original bathroom that the couple plan to redesign next year, and a fluid open-plan kitchen, living and dining space whose sliding doors give on to the peaceful entrance courtyard.

Full-height glass windows bring in light to the exposed concrete walls of the space and everything has been kept structurally as it was originally intended, with a new roof added only for extra insulation. “There were two former owners before us who were also sympathetic to Crowley’s vision,” says MacLean. “So everything is exactly as it was when it was finished.”

A minimal update to the tired-looking interior a few years ago included reinstating terracotta Welsh quarry tiles to replace laminate flooring across the house, and this year the couple have embarked on a complete makeover. “Everything inside our home now is bespoke: we made it ourselves or with collaborators,” says MacLean.

In keeping with the architectural origins, the design-savvy duo have retained original interior leftovers including wooden doors, radiators and steel light fittings by Charlotte Perriand. Modular shelving by Dieter Rams, now full of design and fashion books, lines almost the entire white-painted concrete wall in the living area.

There are bursts of colour everywhere, used as focal points or room dividers, such as the vibrant yellow walls of the showstopper kitchen that match the bespoke cabinetry with an optical graphic print called Sun Loving Bollards by designer Eley Kishimoto.

‘Everything is bespoke’: a view into the living area, with terracotta Welsh quarry tile flooring. Photograph: Edmund Sumner/The Observer

“The house lends itself to colour,” says MacLean. “The rest of the white and grey palettes in the place are muted, so we designed this kitchen with Eley to make a statement and show off our collaborative work.” The kitchen space also includes three unobtrusive Joe Colombo Fresnel wall lights above the hob and the innovative Zip HydroTap Celsius All-In-One, which dispenses instant boiling, cold and sparkling water.

In the master bedroom, a funky space-age-like shower pod with a bright orange door, is a new addition made in-house by Studio MacLean, along with the double bed and wardrobe. The shower walls are lined with an electric mix of mosaic tiles in orange, black, white and yellow, the design of which is inspired by Berlin’s U-Bahn station, Konstanzer Strasse. “We’ve always loved the colour of the walls in that station and we wanted to recreate it here,” says MacLean.

A bespoke teal-green wall cupboard next to a bed fitted into a snug alcove in their son’s room features shelves with unusual yellow storage baskets. “They’re actually old snail crates we picked up in France,” laughs MacLean.

Green light: a teal wall cupboard next to a bed fitted into a snug alcove. Photograph: Edmund Sumner/The Observer

Just as the Eames house was full of colour and collected objects, there is an assortment of mementos the couple have acquired over the years in various rooms, from sculptural ceramics, old architectural models and unusual antique metal shoe kit boxes, to a French industrial clock by Brille and three original posters by graphic artist Hans Schleger that MacLean’s father helped design. “My dad was involved in the fishmonger industry in the late 50s to the 80s, and worked with Schleger to design the posters for a company called MacFisheries. They look great here.”

There is also a covetable mix of furniture design classics, ranging from German Flötotto Profilsystem storage containers and an Alvar Aalto 41 Paimio chair in the living area, to a George Nelson roll-top desk and midcentury string chair by Allan Gould in the study.

“We’ve randomly collected things over the years, but we don’t have a passion for one thing or look at pieces to specifically suit the house,” says MacLean. “We have a home in France, too, so we love going to vide-greniers, and we’ll often swap things between the houses.”

Now their interior mission is almost complete, the family are enjoying their home and despite having planning permission for a second storey, the couple have decided against it. “We don’t want to ruin the feel of the house, so we’ve just focused on creating our dream space instead. It’s most definitely a forever home.”