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New policy to make Westminster a 'retrofit first' city

Westminster City Council has set out new proposed planning policies on retrofitting and affordable housing.

New rules put forward by the local authority will mean developers must explore the option to retrofit before demolishing buildings in the city.

The move will accelerate the upgrading of commercial buildings to meet the modern standards demanded by today’s businesses, cut carbon emissions and help the city become net zero by 2040.

The proposed policy will be consulted on from March 14 for six weeks, as part of a review of the council’s City Plan, the document which shapes the built environment and sets policies for development in Westminster.

The partial review of the City Plan:

  • Puts forward a bespoke policy establishing a retrofit-first approach and clear guidance to developers
  • Supports the delivery of more genuinely affordable housing by prioritising social over intermediate housing in new developments
  • Requires all new residential developments to contribute to affordable housing
  • Identifies four brownfield sites in the city and supports the improvement of these areas with mixed-use development proposals

Cllr Geoff Barraclough, Cabinet Member for Planning and Economic Development said:

We will not reach net zero without a significant shift in how we view development. 

That is why we are introducing one of the nation’s first retrofit policies, promoting sustainable growth by encouraging commercial and residential buildings to be refurbished to the latest standards rather than demolished and replaced with new ones. The policy supports the great work the real estate industry has done to understand how to repurpose buildings to be eco-friendly and attractive to investors, office-workers and people looking for a new home.”  


This partial review of the City Plan introduces a new policy that puts forward a retrofit-first approach. The policy ensures that proposed development in the city supports sustainable growth by delivering energy efficient buildings that contribute to the local and national economy, and to reaching our net-zero goal for Westminster by 2040.

The policy recognises that for some cases demolition and rebuild is the best option, but it encourages developers to fully investigate options for retrofit and extension at the outset, before considering demolition.  Retrofit-first will for the first time assess the whole-lifetime carbon emissions of buildings, considering the environmental impact of demolition, rebuild and the future existence of the development.

The Council’s is proposing to change its approach to the extension of existing buildings when balancing the benefits of retrofit against possible harm to the city’s heritage and townscape.  We will be more flexible in supporting extensions when they unlock retrofit of the entire building. Our proposals recognise that some heritage buildings require improvements to better adapt to climate change impacts and remain fit for the future.

Where demolition is supported, the new policy will also encourage developers to maximise recycling from existing buildings to minimise the environmental impact.  Embodied carbon emission targets will be applied to all new developments, based on benchmarks set by the London Energy Transformation Initiative (LETI). These targets will reduce the embodied carbon emissions for new development in Westminster, currently around 725kg of CO2 per sqm. If the policy is adopted, this could save 480,000 tonnes of carbon between now and 2040, which is equivalent to heating 11,000 homes a year. 

The council recognises that for some buildings, embodied carbon will be higher and so the targets will depend on building type, particularly if homes are being created in the face of high demand and the council’s commitments to deliver more affordable housing.

Affordable housing

The updated City Plan will help to meet the housing needs of Westminster’s families by supporting more sustainable and genuinely affordable housing. The proposed policy will change the requirement of affordable housing split in new developments from 40% to 70% for social housing and from 60% to 30% for intermediate housing.

A new policy will introduce a requirement for sites delivering fewer than 10 homes to contribute to affordable housing delivery for the first time. This means that all residential development will help deliver more affordable homes.

Alongside the partial review of the council’s City Plan, new supplementary planning guidance was put forward for decision on 20 February 2024, which details the type of affordable housing the council wants to see built in the city and changes the approach to intermediate housing so residents with lower incomes get the homes they need. 

Site allocations

The City Plan identifies four sites across Westminster that the Council believes offer the potential for significant mixed-use development. These Site Allocations provide clear and specific policies for four brownfield sites: St Mary’s Hospital, Westbourne Park Bus Garage, Land adjacent to Royal Oak and Grosvenor Sidings.

These sites have been identified as areas where development can make better use of land, support key infrastructure, create jobs, welcome new homes, and/or improve the public realm. The new site allocation policies will set out which uses are suitable for each of these areas while allowing for creative design solutions to unlock the full potential of the areas.

Carbon offset

Independently of the proposed changes to the City Plan, new supplementary planning guidance, subject to a formal decision by 6 March, introduces higher carbon off-setting payments to encourage developers to design more energy efficient schemes. Carbon offset payments are currently set at £95 per tonne of CO2, in line with guidance set out in the London Plan. The new approach and methodology for carbon offsetting means the price of carbon is increased to £330/CO2t for electric-based schemes and to £880 for gas-based schemes.

The 330/CO2t price also applies to new buildings connected to a District Heating Network.

The new approach recognises that the electric grid is decarbonising, and that District Heating Networks can play a role in tackling the Climate Emergency. The policy will help ensure development comes forward while encouraging higher carbon savings on-site. Any funds generated will be spent on carbon-saving initiatives elsewhere in Westminster, contributing to meeting our net zero targets.

Consultation on the proposed policy changes in the partial review of the City Plan will start on 14 March, inviting people to share their views via in-person drop-in sessions, an online survey, and policy-specific webinars.

Cllr Barraclough added:

This review of our City Plan is part of our strategy for a Fairer Westminster, balancing the benefits of new development with our target to become a net zero city by 2040. 

Our proposed changes support the provision of more truly affordable housing across the City and put forward detailed plans in four large brownfield sites to ensure they deliver the new offices, shops and homes we need."

Read the full partial review of the City Plan

Notes to editors:

  • Retrofit definition: Development involving the re-use of at least 50% of the existing building in-situ (by mass or volume), retaining as a minimum the foundations, core, and floor slabs, and which results in energy, performance, and climate adaptation upgrades, which will reduce carbon emissions from the building compared to the existing structure and prolong its usable lifespan.
  • Around one third of housing developments in Westminster are small-scale residential sites, meaning they create 10 or less homes per site
  • Development of the retrofit-first policy has been carried out in conjunction with colleagues in the Town Planning service and with consideration of the guidance on retrofit produced by the Low Energy Transformation Initiative (LETI).
  • The formal Regulation 19 consultation will start on 14 March following the council’s formal decision making process

Published: 4 March 2024