Sanctum, 28-32 Wellington Road, London, NW8 9SP
Duality of Approach to the Public Realm
The form of the building was established with two distinct parts, addressing separately the context and character of Wellington Road to the front, and Cochrane Street at rear of the site. The development therefore reads as two buildings.
Both parts of the building are linked to a shared vertical circulation core containing the lifts and stairs, which is set back from the north and south site boundaries, emphasising the separate buildings when viewed from the public realm. This master plan arrangement allows the creation of balconies and loggias to the corners for the apartments at the rear of each building, as well as addressing the change in site levels between the front and rear of the site.
Wellington Road, to the west, has a more eclectic mix of styles, from listed residential 19th century rendered villas to the south of the site, on the same side of the road, to hospital and residential buildings dating from the 1960’s and 1970’s to the north, and along the south side of the road. In this context, it was felt that a stone façade would provide a distinguished presence in the street scene. The scale of the building seeks to mediate between the 19th century villas to the south and the 1960’s housing to the north.
Cochrane Street, to the east, is predominantly comprised of a series of separate brick clad residential buildings, dating from 1920’s to 1960’s. The Cochrane Street part of the new development is therefore of Roman brick.
Description of the Project
This 7,000 sq m residential new build project, completed in June 2022, comprises 36 apartments over six floors, including a lower ground floor basement car parking. The site has a double aspect, facing onto Wellington Road on the south-west side, and Cochrane Street on the north-east side. The duality of the design addresses separately the context and character of Wellington Road to the front, and Cochrane Street at rear of the site.
The site is situated close to the Metropolitan Line and Jubilee line tube tunnels which run directly below Wellington Road. This presented significant technical design and construction challenges.
The development has a mix of apartments sizes, with external amenity spaces in the form of balconies and loggias. The buildings are set back from the pavement, creating open areas adjacent to the public realm along both streets that are extensively landscaped. Tree pits have been incorporated in the design to allow for the installation and cultivation of mature trees, ones that will be allowed to grow substantially with time.
The Decorative Screens
Bespoke and innovative decorative screens of coloured glass and stainless steel were developed for the Wellington Road façade.
This façade curves out in the central section, ‘floating’ it from the main orthogonal façade. It is broken down into two sections, either side of a central recessive break. Two individual sets of loggias are thereby created at each floor level. The loggias are open, external rooms, and form an extension of the living rooms that they serve, providing a sense of recession and privacy to the main living spaces, whilst at the same time as providing some acoustic screening to the road. These loggias are partially enclosed and screened by stone columns, balusters and the decorative screens.
The screens provide the following:
• Privacy between the two loggias across the recessive central section of the façade
• Privacy at either end north and south against the adjacent neighbours, and
• Low level enclosures to the open aspect of the loggias at second and third floor levels within the Wellington Road frontage
The screens comprise a repetitive abstract composition of triangular stainless-steel frames, linked together in an overall frame. The triangles have inset translucent glass in shades of green. The combination of the triangular shape and the green hue were intended to invoke an abstraction of tree leaves. The repetitive pattern and the multiplicity of the forms, in the context of the loggias they help to define and enclose, evoke a sense of the loggias being within the crowns of trees.
The decorative screens were fabricated by The Steel Group, based in Cremona, Italy.
The screens were accepted by Westminster Council as the discharge of the planning condition that required the provision of public art on the exterior fabric of the building.
The Layered Wellington Road Elevation
The form of the Wellington Road building has been greatly influenced by its proximity to a busy main thoroughfare that runs north out of London from Regents Park. A double facade layer is created. The main, flat, façade provides the weather envelope. A second, curved outer layer is set in front, ‘floating’ out from the main orthogonal façade, and divided into two, with a full height central recessive break.
This morphology creates external loggias between the two elements of the facade. The loggias are accessible from the apartments behind, providing continuous covered external spaces for each apartment they serve. This duality means that the apartments have a more recessive relationship to the road than a conventional façade. The layering is emphasised and strengthened in elevation by the width of the outer façade being set within the overall width of the weather façade behind.
The loggias are external rooms and form an extension of the living rooms they serve. They are partially enclosed and screened by stone columns, balusters and decorative screens. The screens comprise a repetitive abstract composition of triangular stainless steel frames and inset translucent and coloured glass.
The Use of Moleanos Limestone
Stone was considered to be the ideal material to create the layering effect sought for the Wellington Road frontage. Stone has no pre-given shape or size, and it can be quarried, shaped and honed to suit a variety of applications. In this instance, flat, curved and shaped elements were all required for the design, and stone proved to be the perfect material for this. In particular, the use of stone was highly suited to the curved outer façade, which has both inner and outer (i.e. convex and concave) faces in stone; it would have been difficult to create this façade convincingly, and with such presence, in any other material.
The use of stone also allowed just two primary elements in the design of the Wellington Road frontage: stone and the decorative metal and glass screens. This simplifies, unifies and focuses the design, creating an elegant appearance in the street scene.
The choice of Moleanos limestone was influenced by the wider context of the site. It has a geological provenance similar to Portland stone (albeit it is slightly warmer in tone), historically perhaps the predominant stone used in the development of the central areas of London. The use of Moleanos limestone here, therefore, references the wider context of the site, and its prominent position on a major London thoroughfare. In addition, the medium grain and uniformity of colour and texture of Moleanos was considered to be appropriate for the scale of the building, and its contemporary appearance.
The return walls along the north and south elevations of the Wellington Road building are clad in insulated render, in a colour and tone to match the front stonework. At the rear, loggias provide external space on the outer corners. These are framed in Moleanos limestone, as a reference to the main frontage. These loggias incorporate glass privacy screens to the residents and neighbouring properties.
The detailing, fabrication and installation of the stone was undertaken by Gormley Group.
Sustainability and Energy
The building is highly insulated and airtight. The energy rating for all the apartments is B. Airtightness typically is 2.5.
The fabric U-Values are extremely low and far exceed current Building Regulations. The U values for walls, roof and the basement floor are all 0.11 W/m2K. Energy efficiency has been maximised throughout the M&E strategy and in the reduction unregulated energy uses. The high efficiency CHP and gas boilers heating system specified, combined with MVHR represents the most appropriate savings that could be achieved for this development.
The proposed strategy has the potential to provide a 35.64% improvement over the Building
Regulations 2013 minimum target; through passive design measures, energy efficient equipment.
Technical Innovations
The project provided several technical challenges. There are two Tube lines running below Wellington Road, approximately 3m to the west of the site boundary. The crown of the Metropolitan line is located approximately 2 m below the road surface, and was constructed as open cut-and-fill in the early 1860’s. The Jubilee line tunnels are located approximately 20m below the road surface. With two levels of excavation proposed for the new building, there was concern that clay heave would damage the tunnels. Consequently, it was necessary to maintain the current ground loading pattern whilst the excavation was undertaken. At the same time, the design required a compete excavation of the whole of the site for the two new basement levels. This meant that potentially there would be no working area at ground floor for the construction.
The innovative solution devised by the groundworks contractor Trenchco for both issues was to develop a top-down construction methodology. After the permanent perimeter piles were installed, a grid of temporary piles was installed across the site. The ground floor slab was then constructed across 80% of the site, leaving a break in the middle of the site. This facilitated excavation of the basements, providing access for plant, and egress for muck away. The permanent ground floor slab provided a large working area, allowing trucks to access the site and turn around. The area also allowed more than one muck away truck to be on site.
As each basement slab level was reached, the new slabs were installed hung from the ground floor slab. Once the level two basement slab was in place, the permanent columns were constructed up to ground floor. The temporary piles and hangers were then removed.
At the same time, the superstructure could be commenced as the two basement levels were being excavated. This allowed the weight loading to be maintained on the two Tube lines. These were monitored with lasers for movement during the whole of the construction process.
