Walter Segal Self-Build Retrofit

Whilst innovative in their time, Segal-method self-build homes have a low energy efficiency compared to modern homes and are prone to draughts, largely due to the ‘dry’ construction techniques used. Many of the original materials used are also approaching the end of their life, particularly the waterproof membranes and insulation.

Many occupants of Segal-method homes also find them to be ‘tight’ internally – and a number of properties on the street have been extended since their construction, in-line with the original design concept.

The existing house was built in the 1980s and built using the self-build system developed by the architect Walter Segal. The ‘Segal Method’ allowed inexperienced self-builders to construct their own homes using standard sized materials and basic carpentry skills. This was flexible architecture that could respond to the needs of the people who lived within the buildings and could be easily altered as those needs changed.

Over the years the homeowners on Walters Way have made full use of this flexibility; adapting the size and layout of their homes in response to the needs of their families.

Arboreal Architecture retrofitted the house to the Passivhaus standard, upgraded the thermal envelope of the house improving heat loss and solar gain. The entire retrofit has been harmonious and consistent with the spirit of the original design, appreciating its qualities.

Walters Way is locally listed – and recorded on the London Borough of Lewisham’s ‘Local List’, which highlights that ‘alteration to the dwellings is entirely in the spirit of the original concept and in no way detracts from their local historic and illustrative significance’. The full listing is described as follows:

“A development of thirteen timber frame clad houses with flat roofs from 1987. The buildings vary in layout and plan but all are built of the same materials and to the same design. Walters Way was named after the architect, Walter Segal.

One of four phases of a pioneering self-build initiative by Lewisham Council for Borough residents, which began in the 1970s and was the brainchild of the architect Walter Segal. Segal’s vision was a simple modular design that avoided the use of the ‘wet trades’ like bricklaying and plastering and utilised a timber frame clad in standard size materials that were available from builder’s merchants. The simplicity of the design and the use of standard material sizing was to enable easy alterations and enlargements. The beauty of his design meant that these houses, built on deep but narrow concrete foundations, could be built on ground not traditionally suitable for development. The houses were designed to be built by one to two people with extra help required for larger jobs like frame lifting.

Walter’s Way is one of the self largest self-build sites in the Borough and is significant as a representation of Lewisham’s innovative schemes that launched social self-build housing in England. The houses on Walter’s Way have been largely altered which is entirely in the spirit”

Location: South London, Walters Way (Honor Oak Park)

Property type: Walter Segal Modern House

Scope: Deep retrofit and thermal upgrade of a 1980s Walter Segal self-build timber frame house in Walters Way, London, focusing on fabric-first improvements, airtightness enhancement, insulation replacement, and energy performance upgrades to bring the dwelling towards Passivhaus-level efficiency while respecting the original modular self-build construction system.

Key Features:

• Deep retrofit of Walter Segal self-build timber frame house

• Fabric-first energy upgrade

• Improved airtightness and thermal envelope performance

• Replacement of ageing insulation and membranes

• Respectful adaptation of Segal modular construction system

• Low-energy retrofit approach informed by Passivhaus principles

• Extended building lifespan through targeted fabric improvements

• Reduced operational carbon emissions

• Low-impact intervention

• Demonstration of scalable retrofit approach

Project Results:

• Significant reduction in heat loss

• Improved overall building energy performance

• Lower operational energy demand and reduced heating requirements

• Extended lifespan of existing Walter Segal timber structure

• Enhanced indoor thermal comfort and air quality

• Reduced draughts and improved envelope continuity

• Lower operational carbon emissions

• Retention of original self-build architectural character and adaptability

• Improved resilience of ageing 1980s self-build housing to future climate conditions

With Corbett & Tasker Engineers.

Photos by: Agnese Sanvito