Eve Dennehy of Structur Communications explores Origami House, a one bedroom garden building at a family home in West London that features complex geometry in its folded plate ‘origami’ style roof.

Over the past ten years the average age of first time buyers in the UK has been rising steadily and currently stands at around 33 years of age. The high cost of renting privately, the lack of new affordable homes along with spiralling property prices make saving for a deposit out of reach for many young people; unable to afford to leave home, many are still living with parents well into their 30s. To address these hurdles, one family in West London has created a unique architectural addition in the garden of their family home.

Origami House is a one bedroom, open-plan family annexe formed of an unusual Cross Laminated Timber (CLT) folded plate Origami structure. The new building, which has been designed to meet Passivhaus standards, replaces a dilapidated home office in the rear garden of their listed house. The scheme was designed by KSKa Architects who, following their original award winning extension of their client’s home, were given a free hand to reimagine and repurpose the old building into a single storey starter home for their adult daughter.

The main home is located in a conservation area, sitting opposite a Grade II listed Victorian gothic church – an iconic landmark which, now converted to flats, has moved operations to a church hall building adjacent to Origami House. The original outbuilding footprint has been expanded to meet the church hall’s boundaries and replaced with a new build dwelling supported on the original recycled floor slab and piled foundations which have been lowered by 15cm.
“The original flat roofed brick building had little architectural merit except for its unusual polygon shaped footprint which was generated by the geometry of the corner of the garden in which it was sited,” says Matt Keeler of KSKa Architects. “The unusual building footprint was a gift that presented geometric opportunities to re-sculpt the space using a combination of two simple rectangular volumes for the bedroom and dining spaces, arranged to produce a triangular bathroom and polygon shaped open-plan living space.”

“The triangulated, folded plate ‘Origami’ geometry grew from our explorations and, combined with the need to work within the conservation area’s tight planning height constraints, added layers of sculptural complexity to the exposed CLT structure. It was really about working with the existing geometry: what flowed naturally from the polygon shape was to consider how to create the roof in the most elegant way, while overcoming the height constraints. The folded plate roof concept offered the most efficient structural solution to achieve maximum height and volume over uninterrupted 6m CLT spans, but with the minimum thickness of structure. The structural and dimensional properties of CLT made it the natural choice for this project, allowing the creation and expression of a folded plate solution for both roof and structural wall panels.”

Fabric first principles were adopted from the outset and use of CLT was a key element that enabled the enhancement of the specification to aim for as close to Passivhaus standards as possible. The CLT frame is super insulated externally to achieve Passivhaus standard U values of 0.12 W/Sq.mK for walls and 0.13 W/Sq.mK for the roof. The glazing specification has been enhanced to triple glazing. The precision of the CLT superstructure is the foundation to achieving such a high level of air tightness and a high efficiency mechanical ventilation heat recovery unit (MVHC) together with a super insulated air tight envelope means that very little heat is required from the additional warm water underfloor heating.

“As KSKa’s first exploration of structural timber, this small building is a demonstration of the structural, aesthetic and logistical benefits of CLT. Erecting the panels on site was effectively a scaled up version of the cardboard design maquette we made in the office,” Says Matt. “Because we were building in the garden of a private home, it was essential to achieve a fast, clean and efficient build therefore CLT’s speed and ease of construction were key considerations.”

CLT is a clean and tidy method of construction which meant the disturbance for neighbours was minimised with less waste and fewer deliveries and operatives on site. Hybrid construction specialists G-frame Structures who were responsible for the design, supply and installation of the CLT structure were on site for a total of two days with just three operatives and one delivery of CLT.

CLT’s high degree of accuracy also ensured that the complex geometric frame would be pre-fabricated and arrive on site ready to be erected within mm tolerance. Aluminium doors, windows and rooflights were pre-fabricated and fitted immediately the structure was completed meaning it was weathertight within a week. This in turn enabled the fast commencement of cladding and interior fitout.

Internally, exposed CLT provides the finished surfaces of the roof and walls, therefore all electrical sockets and switches were factory pre-cut simultaneously with doorways and window apertures.

“Minimal additional internal finishes were required since the beauty of the CLT structural panels has been left on show,” says Matt. “The owners love the Origami concept and have bought into a Scandinavian aesthetic of exposing the CLT internally. They have high standards and are very into style; they liked the idea that Origami House would have a completely different feel to the main home.”