MIST Phase 1A, Masdar, (GRCA Project Award 2011)

Masdar City, is being built around pedestrians, where open public squares intersect with narrow shaded walkways and connect to homes, schools, restaurants, theatres and shops. The architecture of the city is inspired by the traditional medinas, souks and wind towers of the Arab world.

Considerable effort was expended in the design of the overall facade unit to attain a low carbon footprint, whilst generating a cool living environment to combat the extreme heat of the desert location.

GRC was employed on this project, for the full height of the external facade encompassing the balconies, staircases, ventilation shafts and link bridges.

The facade was originally designed utilizing GRC, by Foster+Partners, to be partially constructed by the Outside-In System and partially by cladding panels. Constraints in the on-site construction methodology, however, saw the facade cladding panels develop into a prefabricated GRC façade module that was prefabricated completely off-site and then bolted on to the pre-aligned brackets cast-in to the concrete structural frame.

By providing flexibility in the use of GRC and pro-actively providing solutions relating to buildability, the external prefabricated GRC façade modules were able to cater for the principal designer’s characteristic complex shapes, whilst providing an integral finish for both texture and colour, with no externally applied finish being required. 

The GRC façade has been designed as a series of curved balconies in a wave pattern that alternates on each floor so when the balcony on one floor is convex the balcony immediately above is concave. 

The colour scheme follows local traditions and other complementary materials combine with the GRC facades to create the whole balcony effect.

When the GRC supply contract was originally tendered, the scope included for only the design and supply of the GRC panels themselves: some to be used in the Outside-In System, whilst other panels would need to have been delivered to site, individually lifted to the building and fixed to the steel structure forming the curved balconies. This is the traditional manner of fixing cladding panels to the structure. The various interfaces between construction trades would have been numerous, requiring large amounts of workers, access scaffolding and lifting equipment. The Main Contractor would have had to co-ordinate all of these.

Through discussions with the Client, the Main Contractor and the design team, the original scope was developed to create a fast-track solution for the facades to the Residential units in which several individual GRC panels were combined to create larger sized panels, thereby reducing the number of moulds and joints between panels.

These larger GRC panels were then installed on to a steel frame, which was coated with corrosion and fire protection, off-site in our factory and delivered to site as ‘one-piece’ units utilizing 40ft open-top containers.

One whole Residential balcony unit (two balcony units combine to form the external façade of one Residential unit) is then simply lifted and bolted on to pre-installed brackets which had been lined and leveled.

Erection of these balcony units originally would have taken up to 10 days for each Residential unit but subsequently the GRC facade modules were fixed in place in only 2 hours.

The deployment of state-of-the-art GRC materials and spraying techniques enabled the GRC to be produced with an optimum percentage of fibre in the mix, resulting in a reduction of its carbon footprint. As part of this process, even the materials and process used for moulding of the panels were assessed to ensure the lowest possible carbon footprint. As an example of this, silicone was used as a liner to form the voids, to create the decorative pattern in the panels. The silicone was able to be re-cycled for use in other moulds.

These issues were fundamental in the approval process for the use of these GRC panels for this phase of the project.

These balcony units are highly complex with the GRC units including openings for lighting; GRC permanent form panels to receive the screed for the in-situ balcony floor above; built-in GRC slatted soffits and ceilings (to look like timber slats, which were originally to be manufactured from renewable source timber); curved GRC panels; and curved GRC screens, all to millimeter accuracy.

Flourosilane sealer was applied to the face of the GRC to provide a waterproof surface that also proved successful in reducing the unsightly visual effect of sand adhering to the facade after sand storms.

The overall visual effect is a GRC façade that meets the client’s and the designers’ requirements, fixed in place to the optimum programme.