Project Profile: Constructing Europe’s largest green wall at Ashford Designer Outlet’s new extension

Officially opening in November 2019, the 9,300m2 extension to the existing Ashford Designer Outlet complex, designed for McArthurGlen by Chapman Taylor's London studio (alongside Applied Landscape Design) and delivered by our Bristol studio, will add 46 retail, leisure and F&B units to the 80 already operating, as well as a new events space and a children’s play area. Reflecting Kent’s status as “the Garden of England”, a living green wall of tens of thousands of vertically-stacked plants will clad the centre – the largest living wall in Europe – greeting affluent long-haul tourists from Europe and beyond as well as day-out shoppers. In this profile, Associate Director Kieran Bradley and Chartered Architectural Technologist Neil Allen talk about designing for the construction of this high-profile development.

What were Chapman Taylor’s roles on this project?

KB: Chapman Taylor designed and then delivered a three-building extension for Ashford Designer Outlet, amending the existing building to ensure the seamless integration of the extension within the overall complex.

The concept behind the extension design was to reflect Kent’s popular reputation as ‘The Garden of England’, and so an ambitious living green wall – the largest in Europe – was incorporated as a major focal point of the project. Work started on site in January 2018, and is now approaching completion after a 21-month construction process.

NA: The brief for the extension was divided into a number of phases. The first phase, with which we had little involvement, was to create a new car park at the southern end of the site to allow for the repurposing of the existing car park site for the new extension. Phase two then involved constructing three blocks, one of which extends out over the old car park while the others form two “arms” reaching out from the existing building.

The food courts at the northern end of the site were demolished to enable the curtailment of a site-wide tensile canopy structure, allowing for the construction of the extension buildings.

The whole extension project was conceived by our client, McArthurGlen, as an opportunity to revamp the whole retail experience and to create a flagship designer outlet centre for the UK – this design, along with the living wall, helps achieve that.

Tell us about the extension buildings

NA: The extension buildings were simple in design and construction – two-storey, steel-framed structures with SFS infill and single-ply flat roofs. Some of the façades make use of insulated render, while the rear elevations of blocks one and two used brick and block cavity walls up to first floor-level and then metal composite cladding.

Although the building typology was fairly simple, the geometry of the building design was complex, with faceted façades behind the living wall system to create a sweeping façade effect. This required a lot of early involvement with the structural engineers (Cundall Engineers) and the main contractor (McLaren) to establish fundamental setting-out principles for the façades at the perimeter of the ground slab, and their relationship with the building envelope and structural grid.

The original building was designed by Richard Rogers (Baron Rogers of Riverside) in an oval shape and covered by a fantastic, oversailing canopy, designed by tensile structure specialists Architen Landrell – it was necessary to ‘cut’ the ends off both this canopy and the buildings below it to enable the construction of the new extension, which provides 46 new units (with the flexibility to house 50, if required). The extension will accommodate several big-name outlet stores, including Hugo Boss, Polo Ralph Lauren and Joules, as well as F&B brands such as Five Guys and Comptoir Libanais.

The interior public and centre management amenities, which take up the entire first floor of block 3b, are split between an office suite for centre management, public toilets and a public waiting area. The client designated a large budget to this part of the scheme, which enabled a very high level of specification and bespoke detailed solutions – employing specialist interior designers Carden Cunietti to provide a concept design for the spaces. It was interesting working with them as their design process is quite different from ours – we collaborated with them, and dedicated a lot of time and attention to progressing the detailed design of the internal fit-out for the public amenities to ensure that their excellent concept intent was successfully integrated with the overall building design in a compliant manner.

KB: The extension was designed to match the heights of the existing complex, with the canopy amended by Architen Landrell to integrate the extension visually with the rest of the centre. The extension buildings themselves provide a refreshing contrast to the existing development, being more like modular containers – the green wall façades create a sense of those structures being part of a garden space.

KB: Our shell & core design and delivery for the extension has achieved BREEAM Very Good certification for sustainability and an air permeability rate of 3m3/(h.m2) @50 Pa.

There is also a large public realm element to the scheme, designed by Applied Landscape Design. Between blocks one and two there is an external landscaped space with lots of seating, planters and other furniture which combine to create a static, relaxing place in which to dwell. Towards the rear of block three, there is a new, state-of-the-art children’s play area flanked by walls decorated by Berlin grafitti artists art-efx and a small plaza lined with F&B offers, creating a vibrant space for shoppers to enjoy.

What other innovations did the construction process require?

NA: On the front end of block 3A, there are two major curves – working with curved buildings was a first for me! The curtain wall module and glazing itself is curved. We had been advised by glazing manufacturers that only a couple of companies in the UK manufacture this type of glass, so we were fortunate that the main contractor didn’t value-engineer the design to a faceted curtain wall due to cost or long lead-in times. The end result looks great – which shows that McLaren were very committed to our original architectural design intent.

The biggest innovation was the incorporation of Europe’s largest living green wall as part of the extension development – 2,200m2 of pre-planted modular panels to achieve what is, in effect, a large rainscreen façade system made from plants. Working closely with the appointed living wall specialists Biotecture, we were able to fully understand the living wall system and installation sequencing, along with any limitations, allowing us to fully coordinate the setting-out of the modular panels, irrigation system and drainage across the façades of the building while maintaining our architectural design intent. All of this had to coincide with the setting-out of various other packages of works, such as the feature flashings on shopfront glazing, granite plinths, various rainwater goods penetrations and bracketry for fixtures such as external feature lighting and shop blade signs.

KB: It was also a big investment by the client – it comes with a high maintenance cost and will need regular looking after – so it was important that the installation was carried out in a way which would facilitate future care. We worked very closely with the specialist living wall subcontractors Biotecture to this end.

It was very interesting to learn about the irrigation systems required and how they are installed. It is also just very nice to stand on site and appreciate the living façade – it looks great and helps create a relaxed atmosphere in keeping with the principles of biophilia. The plants move in the wind, which creates movement across the façade, something which you don’t see in more traditional cladding.

What were the challenges in installing such a large planted structure entail?

NA: Our main role was to coordinate the technical requirements with the wall panel sizes. Biotecture has its own nursery in which it grew appropriate plants within the panels, which were then brought to site once the plants were sufficiently established. These panels were then constructed in place along with the irrigation systems required.

The biotecture system specification is very complex, with a pump room required for each building and an irrigation system specifically tailored to the plants included. The irrigation was organised so that one plant room serviced each block, with those plant rooms being controlled remotely via Wi-Fi – the irrigation system and plant feed quantities can thus be monitored remotely from off site. Unlike other systems, there is no soil included and all the nutrients for the plants come from the water, which means it was very important to get the irrigation system right. This makes the system a little more expensive in the short term, but will pay dividends in years to come when the plants continue to grow and thrive.

KB: The infrastructure under the site had to be coordinated very early on – it was a challenge to ensure that the various services were all in place and efficiently laid out where they needed to be before the extension was built above – a lot of careful thought was required.

How was the multi-phase, multi-contractor construction programme coordinated?

KB: We designed everything in BIM Revit and then developed the Employer’s Requirements information to enable the main building contractor, McLaren, to issue tenders for various subcontractor roles on site. That gave us a solid grounding for coordinating the subcontractors as they came on board and throughout the development process as design information started coming through from them.

We issued DWG and pdf files, on which the other contractors could then perform their own work. We then brought all the information together within our own BIM Revit model, acting as design coordinator. There have been client-led design changes along the way, even during or after construction, so ensuring that the various contractors were implementing the adjusted designs was occasionally a challenge.

There have been several companies involved in the successful delivery of this project, but Chapman Taylor and McLaren were at the core of leading and coordinating the development.

What do you take most satisfaction in from the project’s delivery?

NA: For me, the coordination of the green wall’s construction was particularly gratifying, as was the sheer size of what we delivered in general – a £50 million+ scheme with up to 50 new units – and it has been a great lesson for me in coordinating a project on this scale. The extension works really well – it looks like it belongs with the existing development, visually blending in seamlessly.

KB: McLaren, the main contractor, is very happy with how everything has gone on site, and the client, McArthurGlen, has expressed delight with how things have progressed and happiness with our performance – particularly how well we coordinated the project.

Given the time constraints involved and the number of subcontractors and subconsultants involved, that is something of which we can be rightly proud.

Key facts:

Sectors: Retail, Leisure
Services: Architecture
Client: McArthurGlen
Area: An extension of 9,300m² GBA
Status: Due to launch in November 2019
Sustainability: BREEAM Very Good (Shell & Core)

Kieran Bradley

Associate Director, Bristol

Kieran Joined Chapman Taylor’s Bristol team as an Associate Director in March 2017 and performs an operational lead role within the Bristol studio while leading several project teams through the detailed design and delivery stages.

Kieran has over 20 years’ experience working in architecture, leading delivery teams on a range of private and public sector projects across the UK - including major mixed-use, residential, MoD, healthcare, and science & technology schemes.

His strengths lie in leading the technical delivery and construction periods of projects, and he understands the importance of communication and relationships within the design team and with the main contractor to ensure the successful delivery of projects.

Areas of expertise:

Design Management/Delivery/Residential/Office/Retail/Mixed-use/MoD/Healthcare/Science & Technology

Kieran Joined Chapman Taylor’s Bristol team as an Associate Director in March 2017 and performs an operational lead role within the Bristol studio while leading several project teams through the detailed design and delivery stages.

Kieran has over 20 years’ experience working in architecture, leading delivery teams on a range of private and public sector projects across the UK - including major mixed-use, residential, MoD, healthcare, and science & technology schemes.

His strengths lie in leading the technical delivery and construction periods of projects, and he understands the importance of communication and relationships within the design team and with the main contractor to ensure the successful delivery of projects.

Areas of expertise:

Design Management/Delivery/Residential/Office/Retail/Mixed-use/MoD/Healthcare/Science & Technology

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