A Striking Curved Extension to a Georgian Townhouse
The Sun Rain Room is a two-story extension and restoration of a Grade-II listed Georgian townhouse, which serves as both studio and family home. The extension reframes the rear, amplifying the characteristics found within the building fabric.
The extension is a landscape, animated by the sun and the rain, comprising a green roof, garden room, reflecting pool and sunken light well. It is a place to enjoy changing weather conditions, seasons, and times of day.
On the ground floor, the garden room is enclosed by a curved glass wall, and spills out into a covered outdoor area containing a workshop, cooking area, potting shed, recycling bay, and store; prosaic functions are hidden by a sliding mirror wall. The enclosed spaces look out across a patio, below which the extended basement creates a new bedroom, two bathrooms, and utility area.
Building methods
The perimeter walls of the rear courtyard support a plywood roof, cut in plan to allow maximum light, following the path of the sun. The sweeping form that emerges frames the view back towards the Georgian terrace. An etched glass staircase bridges the patio and the house, below which an enlarged plant-filled light well brings life and light to the basement.
The roof is a thin 110mm structural shell perforated with round coffered skylights that echo the wave pattern of raindrops landing in the pool. The structure is built up in layers of CNC cut birch plywood to form a stressed-skin with an insulated core. The coffers join the upper and lower skins together and are arrayed in a diagrid to better transfer forces to the perimeter support, whilst an integrated upstand beam on the leading edge increases the span-to-depth ratio.
Sustainability
On the ground floor, heat loss from the large glazed wall is minimized by double glazed, double laminated glass units with integral low-e coatings. By insulating the party wall, and developing an innovative plywood stressed-skin roof structure with integral insulation, the space requires minimal space heating.
The new waterproof concrete basement structure removes the need for a secondary waterproofing system or mechanical sump pump. The insulated box has a very high thermal performance. By extending the light well, daylighting has been significantly improved and an effective passive ventilation strategy introduced. The sophisticated lighting system is comprised of low energy LED fittings.
The green roof contributes to sustainable drainage; harvested rainwater fills the pool and irrigates the sedum.
Project: Sun Rain Room / Location: London , United Kingdom / Architect: Tonkin Liu Architects / Area: 80m2 / Completion: 2017 / Photograph: Alexander James
