Chowdhury Walk is an award-winning part of a new housing programme by Hackney Council to develop small, underused sites. Architects Al-Jawad Pike designed the row of 11 houses to be an alternative to standard terraced housing, with each home rotated slightly to create a varied streetscape.
Brick-clad timber frame blends with the local vernacular, while the ‘twist’ design adds novelty; © Rory Gardiner; courtesy of the Wood Awards
Completed in 2022, seven of the houses are available for social rent. The project, described by the RIBA as “an exemplary blueprint for social housing”, was shortlisted for the 2024 Stirling Prize and won the Neave Brown Award for Housing – the annual award for the UK’s best new affordable housing.
Let’s twist again, like we did next door
The site was previously home to some garages and a community allotment that was relocated. Al Jawad Pike’s design reimagines the terrace with a literal twist: each house is rotated at an angle and then stepped.
The gesture of “twisting” the house came about for several reasons: the first of which was essentially to break up what would otherwise have been a long block of repetitive windows and doors – to create something that had a play of light, a play of mass and sculpture to it.
“Imagine a standard terrace in which each house has been twisted and then slid apart,” suggests Richard Heath, Director at Momentum, the project’s structural engineers. “The ‘twist’ adds some filigree to it – it gives it a pattern. While they are still all terraced houses, the street feels a lot more characterful.”
“It’s a clever design idea and it increases the façade area per unit, which increases the opportunity for light. While that extra façade might be a little more expensive, there is the added quality of life benefit for residents of light from two directions.”
The twist brings in an overhang: in each house the front bedroom overhangs the ground floor, creating a porch of sorts. These carved-out entrances add architectural character while reducing overlooking on neighbours. “That required the structure to cantilever, but there’s no steel in there,” Richard explains. “It is simply the CLT wall acting as a deep beam and cantilevering out. There is a CLT floor panel that then screws into the bottom of that beam.”
The carved-out porch enabled by the ‘twist’ design adds privacy; Brick-clad timber frame blends with the local vernacular, while the ‘twist’ design adds novelty; © Rory Gardiner; courtesy of the Wood Awards
Keeping the carbon down
The design addressed the challenges of both operational energy and embodied carbon. The homes are constructed in cross laminated timber (CLT), which is exposed internally in places, although they are clad in red brick.
The 330m³ of CLT was supplied by Egoin, made from Egoin’s local Spanish radiata pine. Three cubic metres of glulam was also supplied: glulam beams were used under a stair in each house, for trimming the stair void.
In total, that means the houses effectively sequester 240 KgCO₂eq/m² within them for their lifetime. Use of timber keeps the project’s upfront embodied carbon emissions low: 142 KgCO₂eq/m².
Operational energy
The houses have solar panels on their mono-pitched roofs, which create a wave-like effect down the terrace. The onsite renewables generate 6,732 kWh/year, with a typical operational energy of 25031 KwH/m²/year. Passive solar heating and natural ventilation were implemented as passive environmental strategies.
Window sizes and placement were carefully considered to optimise passive solar heating and the predominant wind direction to reduce the heating energy demand and reduce summer overheating. They are triple-glazed ‘punched windows’: there is no visible lintel as such, just an aperture in the brick façade. This complements the stone plinth feature that runs around the ground floor front of each house.
Work in progress at Chowdhury Walk
“The alternative would have been to have had the brickwork coming right down to the ground,” says Richard. “The plinth adds some balance and provides a base for the planters.”
Water and drainage
The project incorporates SuDS (sustainable urban drainage systems) and achieves a surface water run-off rate of 5 litres per second. Cobbled paving to the mews and rear gardens is substantially permeable.
Soft landscape runs along the north boundary wall of the site, acting as a rain garden. Due to London clay across the site and a lack of existing ponds, a below ground attenuation tank of 39m3 was integrated to retain a 100-year 60-minute return period storm – including a 40% climate change allowance.
A Vibro Stone solution
The ground quality was far from ideal on site – it was poor ‘made ground’. If strip footings had been used, they would have had to have been quite deep. As a cost consideration, the contractor looked at using Vibro stone columns – which had an added low-carbon benefit.
“Essentially, you drill core holes in the ground and fill them with stone to provide the equivalent of piles and place a shallow footing on top,” Richard explains. “It improves the ground without using cement. You save a lot of concrete, a lot of excavation, and a lot of embodied carbon. They are a good solution, particularly for low-foundation loads.”
Timber proves cost-effective
It was not always a given that timber was going to be used. “We did look at the scheme in load-bearing masonry,” Richard reveals. “The team put together an outline design and looked at different ways of achieving it. And the CLT option was preferred.”
A ‘pleasingly elegant’ scheme; © Stale Eriksen; courtesy of the Wood Awards
Council-provided social housing has to be demonstrably good value, and the timber option was price-competitive against other materials: it lent itself to the formal repetition in the project, while the associated speed of construction was also a factor. Construction began shortly before Covid and the timber frames were put up during lockdown.
“In some ways, timber frame was hugely advantageous because it need not require many people,” Richard recalls. “In terms of Covid and minimizing risk, it was unexpectedly advantageous.”
“It’s a pleasingly simple and elegant timber structure – no flashy show-off features,” he concludes. “It is a housing scheme, built with timber panels, that also happens to be a great bit of architectural design.”
