ABC+D reports on precast cladding panel projects

ABC+D brings you a discussion on the versatility of architectural precast cladding panels by Stephen Maddalena, shown through two different projects.

Stone-faced precast concrete units consisting of 50mm thick natural Portland stone provided an alternative method of construction at an office development where site location and programme constraints could not accommodate its being built traditionally with handset stonework.

The Rolfe Judd Architects' designed office development at 8-13 Lime Street at the heart of the City of London, is within the Leadenhall Market conservation area.

The requirement for it to be predominantly constructed using natural Portland Stone was not possibe due to site location and programme constraints.

With no opportunities for compromise, a suitable alternative method of construction needed to be selected.

For the main Lime Street and Lloyd's Building elevations, this was achieved using the precast units with Portland Stone quarried and dimensioned by The Stone Firms at Portland, with a 150mm backing of reinforced concrete.

For the Beehive Passage elevation, Rolfe Judd's design showed brickwork that was similarly developed into brick-faced precast concrete units to facilitate construction.

The detail design of the stone-faced and brick-faced panels was then further developed to enable window apertures within the typically storey-height panels to be framed and glazed before despatch.

Because of the site's restricted location, cladding panels were delivered on a just-in-time basis for direct off-loading and hoisting to their final locations.

With the precast panels spanning between the floor slabs, the need for a secondary backing structure that would have otherwise been required for handset stonework was avoided.

Without such backing structure, access to the internal face of the panels and their support and restraint fittings is unobstructed; the panels can consequently be safely and efficiently fixed without the need for an external scaffold.

By effectively pre-assembling the stonework and brickwork requirement of some 1,400m2 into 300 panels, the building was able to be clad in 12 weeks with shared use of the main contractor's tower crane.

By contrast, Temple Quarter, around Temple Meads station in Bristol, is a 115-acre regeneration project that is becoming the new heart of this city's business centre as it continues to attract major financial, legal and government organisations.

The latest phase is Temple Quay Central, which includes new offices for Burges Salmon who provides legal advice to national and international clients.

Now to be named 1 Glass Wharf, the 29,000m2 ND3 building designed by Stride Treglown Architects is being constructed by Balfour Beatty.

Like Lime Street, and for many of the same reasons, including highquality appearance with inherent robustness and durability, architectural precast cladding panels also feature in its construction.

Totalling some 3,000m2 in 400 typically storeyheight units, its precast cladding panels have been produced with a reconstructed stone finish instead of natural stone or brick facings.

Cast by The Marble Mosaic Company using a grade 45 concrete mix of Polar White dolomite aggregate and white cement, the exposed surfaces have a lightly textured surface to produce a sparkling white appearance.

While it is typical for precast cladding panels to be individually supported by a building's structural frame, the detailed design of the precast cladding panels for ND3 was developed to enable them to be stacked up to seven storeys high to facilitate their fixing to stair core walls.

Although the locations and design requirements of 10 Lime Street and 1 Glass Wharf are very different - one a particularly restricted site surrounded by an established international business centre, and the other a waterfront location that is being progressively regenerated - both exemplify the inherent versatility and practicality of architectural precast cladding construction.

Whereas the precast cladding panels for Lime Street were predominantly faced with natural Portland stone, the white concrete mix with etched finish for Glass Wharf provides a similar colour and surface texture with comparable long-term weathering performance.

These very different cladding solutions have both been designed to provide a trouble-free service life exceeding 60 years, and a high degree of energy efficiency for the buildings they enclose, taking advantage of the thermal mass of concrete to reduce peak heating and cooling loads.

As importantly, precast concrete cladding is increasingly being recognized as being particularly sustainable.

It is a resilient, energy efficient, low maintenance and durable cladding material with its manufacture taking place in low-energy, resource efficient and low-waste production facilities, managed and staffed by a skilled workforce, using responsibly resourced materials.

Moreover, the direct and incidental benefits of precast cladding construction are increasingly being recognised as providing optimum value for new commercial and civic offices, retail schemes, hospitals, residential and leisure developments as well as new buildings for the educational and judicial sectors.

Back to top