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RetroFirst stories: How HÛT changed tack from AHMM to revive 1960s office

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The latest in a new AJ series looking at architects who have saved buildings from the bulldozers or brought them back from the brink of ruin

RetroFirst Logos 2019 3

RetroFirst Logos 2019 3

With up to 40 per cent of carbon emissions coming from the construction industry, the profession needs to find ways of adapting the type of buildings it designs, and fast.

In order to tackle the climate crisis, the default – and less carbon-hungry – option for any project should be to adapt and reuse an existing building, one of the key demands of the AJ’s RetroFirst campaign.

With the spotlight on retrofit, our ongoing series seeks to celebrate the projects that save buildings from ruin or demolition and to hear from the architects that designed them.

Today we hear from Alex Arundel, senior architect at HÛT Architecture, about how the practice took on the tricky revival of 1960s office after previous plans by AHMM to demolish the block and replace it with homes was withdrawn.   

Hut architecture dorset gardens collage

Before (left) after (right)

Before (left) after (right)

What is the name and location of the project?
Dorset Gardens is in central Marylebone next to Paddington Street Gardens. The site is accessed via a covered passage between  two street frontage properties; which gives the site the feeling of entering a secret garden. Inspiration for the scheme came from the site’s proximity to the Paddington Street Gardens and a desire to green the development. The project includes the retrofit and extension of an existing 1960s (B1) office building, known as Midori House, for modern day use.

What were the challenges of the existing building?
The restricted access via the entrance passage way beneath neighbouring buildings makes any construction more complex. The impact on the surrounding residential amenity, daylight and sunlight and overlooking were all key considerations during the development of the scheme.

It was also important to make this project contextually appropriate given how close it is to the historic Paddington Gardens.

Other challenges included the current site levels which prohibit level access, tired façades with a piecemeal materiality and single glazed windows in poor repair.

In relation to regulatory challenges the site is located outside of the Core Central Activities Zone (CAZ) but within the wider CAZ.

Westminster’s planning policy for areas outside of the Core CAZ restricts commercial extensions and developments which was a significant challenge to overcome. The project was successfully granted permission at committee in March 2020 for an additional 18 per cent increase in floor space to the building despite local policy restrictions. 

Had demolition ever been considered?
Yes, a previous scheme was developed by AHMM in 2015 for the complete demolition and new build of a residential development which included six apartments over five floors, along with a double basement (pictured below). This application was withdrawn due to the impact on the neighbours and a more sensitive approach to a refurbishment scheme was explored.

Ahmm dorset garden 2015 withdrawn

AHMM’s earlier proposals for Dorset Gardens from 2015 which were later withdrawn

AHMM’s earlier proposals for Dorset Gardens from 2015 which were later withdrawn

How did you convince the client not to flatten the building?
Studies proved the existing building was not fit for purpose for residential conversion. The standard of accommodation would have been poor. Therefore, the client decided to change tack and retain commercial use on the site. This led to studies of how the existing building might be upgraded and extended. Through materiality studies we managed to persuade the client that a dramatic improvement could be made to the building without the need for demolition.

There were mulitple benefits of a retrofit scheme: it would improve the chances of an approval with Westminster Council; it would reduce the impact on the neighbouring context; the reuse of a structurally sound and well-planned building with double aspect floorplates would lessen the environmental impact; the cost and construction time would be reduced.

Aside from retaining the original fabric, what other aspects of your design reduce the whole-life carbon impact of the building?
A number of design features have been incorporated into the proposal to ensure it is a more efficient and sustainable building. Upgrading the facade includes the installation of new insulation, a brick skin cladding and all new high performance glazing.

The MEP services in the existing building are dated and fall considerably below the expectations for modern office space. All of the office spaces will be provided with natural ventilation, introducing outside air flow whilst making use of the quiet location. New lighting will be low energy with the offices benefiting from high levels of natural daylight.

The existing site currently doesn’t offer much in terms of greenery and ecological value. It is dominated by extensive hardstanding and parking provisions for 14 cars, littered with ad-hoc plant, untidy bins and bike racks.

The proposed scheme incorporates wildflower green roofs to all new extensions connecting the site conceptually to the adjacent gardens. The green roofs improve neighbouring residential outlook, as well helping with attenuation of rainwater flooding and pollution problems in London. All offices will have access to private external amenity areas either within the ground floor courtyards or the refreshed existing balconies to the Paddington Gardens elevation.

In order to ensure its long term viability, improvements are proposed to provide better access to the site in line with current regulations. A full suite of new amenities are provided within the extension and existing basement including dedicated bike storage, shower facilities, accessible WC/showers, lockers and changing room facilities. Vertical and horizontal circulation is also upgraded and extensive waste and recycling storage planned.

Model 2

HÛT Architecture’s plans for Dorest Gardens - model

HÛT Architecture’s plans for Dorest Gardens - model

Were the planners supportive of the proposals?
Due to the current policy within the Westminster, commercial extension schemes are not supported outside of the Core Central Activities Zone (CAZ) therefore the application had to offer far more benefits to outweigh this restrictive policy. The ambition was set at the beginning of the project to conceive a technically perfect planning application and scheme which would be difficult to refuse.

The design team collectively studied and agreed upon a modest amount of new massing which did not impact the residential neighbour’s amenities but improved their outlook. The proposals aimed to go beyond Westminster’s guidance for commuter facilities, refuse storage, accessibility and external plant provisions.

All of the above provisions resulted in a well-received application which was unanimously approved by the Planning Committee in March 2020 with the support of local residents.

What have been the main lessons from the project that you could apply on other developments?
The relatively cost effective application of an external cladding system to completely change the external appearance and setting of the building with the added benefit of incorporating thermal upgrades. This could be used on many urban retrofit projects.

The strong concept to green the site and restore a garden setting helped guide all design decisions and resulted in a stronger proposal. Defining a clear strategy and concept from the outset reaffirmed the importance of this approach to lead a design and consultant team.

Drawing 1 ground floor plan

HÛT Architecture’s plans for Dorest Gardens - ground floor plan

HÛT Architecture’s plans for Dorest Gardens - ground floor plan

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