A rooftop extension fronted by a grid of metal mesh and glass contrasts with the original brick facade of this building in east London renovated by Duggan Morris Architects (+ slideshow).

Duggan Morris Architects was tasked with adding three storeys of office space to the four-storey Georgian property in London's Shoreditch. As the building sits within a conservation area, the architects were required to preserve the existing residential facade above the ground floor shopfront.

"The challenge was to retain the domestic scale windows within a commercial office use, as well as to consider the proportional impact and aesthetic quality of the multi-storey addition," said studio founders Joe Morris and Mary Duggan.

Behind the brick facade, the building has been completely remodelled to generate an interior suited to modern commercial uses. The basement and ground floor are dedicated to retail, but the rest of the floors all provide flexible office spaces that decrease in area towards the top.

The Curtain Road facade features a grid that divides the surface of the extension to correspond with the three bays of the original frontage. Local rights of light required some open sections at the rear to become roof terraces.

A recessed section at the top two storeys reveals a portion of the adjacent building's flank, helping to anchor the extension into its surroundings and creating a small terrace.

The new facade was designed as a simple arrangement of horizontal and vertical units, rendered in visually lightweight modern materials to create a contrast with the existing brickwork.

"To retain the gravitas and independence of the urban block, the additional storeys are designed with an ambition to achieve a lightweight object quality, restrained from any references to the adjacent heavy masonry structure," the architects explained.

A combination of bonded glazed units and panels covered in a wavy metal mesh were installed to create a flush surface with minimal jointing and surface detailing.

The metal panels are perforated with a pattern of holes that allows air to flow through and doesn't obstruct views from inside.

Felt curtains that can be drawn across the large windows create a similar visual rhythm to the undulating surfaces of the mesh panels.

Concrete lintels and cills are painted in a matte finish, as are the window frames. The anodised metal panels have a champagne finish to ensure consistency between the masonry and the new architectural features.

Towards the end of the construction process, a neon lighting installation by artist Tim Etchells was installed in one of the windows, displaying the message "Shouting your demands from the rooftop should be considered a last resort".

Photography is by Jack Hobhouse.

Here's a project description from the architects:

Shoreditch office extension

This is a speculative office development generating 20,000sqft (GEA) of retail and work space located at 141-145 Curtain Road, Shoreditch, East London. The project is located within a conservation area defined by Georgian brick buildings and requiring retention of the existing urban block.

The building prior to development was four storeys (G, B+2) in height and is fully remodelled behind a retained brick façade. Above this, three new floors of contemporary office space are added, extending the building to 7 storeys in total, almost doubling the usable area. Planning permission was obtained in September 2011. Construction commenced in November 2012 and completed in October 2013.

The scheme

To generate the required area of 20,000sqft, a further three storeys were necessary within the permissible building footprint which is defined by the alignment of the front facade at street level and the rights of light (RoL) envelope at the rear. There are 7 floors in total (B, G 1-5) diminishing is size as you ascend. Logic and efficiency dictate the plan arrangement. A compact circulation core contains toilets, showers, lift and stair, and is orientated on the tallest side of the building. The offices are maximised with external terraces also carved out of the RoL envelope.

The ground and basement are intended for retail use. As such two entrances at ground level occupy either end of the facade - 141 leading to the upper office levels and 145 directly into the retail unit. Ultimately the building is flexible and can accommodate a single or multi tenant let. To retain the gravitas and independence of the urban block, the additional storeys are designed with an ambition to achieve a lightweight object quality restrained from any references to the adjacent heavy masonry structure. Scale references to the adjacent buildings window punctuation are stripped back by reducing the extension to optimum modules horizontally and vertically. The materials are reduced to mesh and glass with minimal panels and visible jointing. The lack of reveals to windows are intended to further communicate the delicate object form by disguising the depth or make-up of the construction.

This object quality is further reinforced by the deep recess to the upper 2 storeys. By revealing a portion of the existing brick flank to the adjacent building block (139 Curtain Road) the weight of the existing fabric is further communicated. This obviously reduces nett lettable area but is counterbalanced by a maximised envelope to the rear. Also the precise fit of the building between party walls without visible overdressing of flashings is intended to allow the extension to read as an independent form intended to appear simply resting 'upon' the facade below and 'between' the adjacent warehouses. A 50mm gap is detailed between the existing masonry and the extension and projecting copings are omitted in lieu of self-draining window sections.

A grid is imposed on the front facade to respond subtlety to the 3 bay house facade below. The plot is trapezoidal in plan and as such a diagonal grid sets up positions of facades and balustrades to the rear. The grid is further enforced at the rear, with smaller staggered terraces, articulating the building where the mass responds to a RoL envelope. Thus a proportional logic of panel size - mesh and glass - is utilised across the facades with the positions of balustrades also defined by the RoL envelope.

Materials & colour

The visible facade is made up of mesh and large bonded units. The principle behind the entire facade construction is to use a simple curtain walling system where possible, with bespoke inserts to achieve the non standard details. The bonded glazed units are tied back to the main super structure. The mesh is bracketed off the curtain walling to meet the same plain as the bonded units and to achieve the flush outer layer. This principle continues around the entire facade front and rear. In order to maintain a reading of the building as a whole the colour palette is carefully calibrated to respond to the masonry tones from grey concrete mortar to mid brown bricks. The reflectance of the materials increases as you ascend to sky and the textural quality of each material selected is emphasised by various means.

A champagne coloured anodised metal panel is used for the mesh on the upper storeys. This is perforated with small holes achieving 40% free air flow and is also calculated to appear almost invisible from the inside to retain views across London. A waved profile adds another layer of light quality maximising incident sun throughout the day. The anodised surface is iridescent in sunlight.

The transition from the mesh to the glazed bonded panel is carefully managed by introducing a matching fritt within the double glazed bonded unit. This softens the overall appearance of the glass which would normally be a contrasting frame and fritt colour. Felt curtains have been introduced to the larger windows fronting onto the street to extend the waved mesh detail across the entire facade. The brick has been lightly cleaned and repointed where spalling with the intention to retain the relic with minimal surface alteration. All concrete lintels and cills and window frames are painted a matt colour to match the brickwork attempting to simplify the reading of the retained element.

At ground level the shop front is framed in concrete supporting the building mass above. The glass panels within being as large as is permissible with the constraints of the tight street and working zone. Again a fritt has been selected to match the concrete colour to soften the junctions. The colour treatment stops at the facade. As a rule the entire office units are white including light fittings and all exposed services.

Theatre

The building has been a challenge in many respects mainly imposed by the condition to retain the existing facade. To an extent the process to retain it required extensive counter intuitive construction works. The delicate quality of what is deemed to be 'permanent' and of historical value has been exposed through the very process of having to retain it. An installation by Richard Wilson at Liverpool Biennial 2007 entitled 'Turning the place over' played on this very condition. A permanent gritty piece of city fabric is explored as an adaptable component. An abstract portion of the facade was mechanically rotated exposing the inside.

Similarly, this revelation of the building fabric became an interesting part of the construction journey that was to be capitalised upon particularly given the visibility of the works from the street and the opportunity to promote the building as a theatrical contribution to Shoreditch, perhaps calling out to a particular tenant typology or exposing a opportunity to use the building in an unconventional way. The construction works required an oversized steel temporary structure to protect the facade from falling which needed to be pinned back to the superstructure. The entire shopfront below was removed leaving the brick facade suspended to allow alterations to take place behind it. Due to the close proximity to the street and the restrictions imposed by the Olympics 2012, temporary scaffolds and coverings were kept to a minimum thus the entire build process was evident throughout the construction phase. Due to the size of the bonded panels a complete weekend closure of Curtain Road to permit safe cranage positioning and installation was necessary.

An installation by Tim Etchells was exhibited to expand upon the theatrics. The piece was installed for 6 weeks from September to October 2013. The neon piece entitled 'shouting your demands from the rooftops should be considered a last resort' was selected for its obvious irony in the context of imminent marketing of the building, but also to demonstrate the opportunity to use the high level glazed pods for exhibition. The neon had the obvious benefit of retaining visibility during the dark early evenings.