Adaptability at The Acre

ACO overcomes installation challenges to provide sustainable drainage to an iconic London building renovation. Specify & Build reports.

When a blue roof was needed as part of a major sustainable renovation at the Acre in London, it was vital that the solution specified could be installed while other work on aspects of the roof were underway.  

The brutalist building – previously known as 90 Long Acre – was built in the 1970s and, by 2020, was in need of major renovations to restore its status as one of Covent Garden’s architectural highlights. The 240,000 square foot building would include office spaces, a café, and 113 residential flats.  

Boosting The Acre’s green credentials meant overhauling several key systems including the heating, the electrical supply, and roof drainage. With conditions around the site meaning storage space was limited, deliveries had to be carefully planned and ACO’s fast adaptability proved a major advantage.  

ACO Building Drainage was invited by building design firm Arup to collaborate on the roof drainage part of The Acre’s renovation. ACO visited the site and provided calculations for the water attenuation the building would need, recommending products that could provide the attenuation required, in line with the overall sustainability goals and planning conditions of the project. 

ACO’s calculations accounted for the different sections of roof and the fact that raised areas of the roof drained onto lower parts. The provided calculations also took into consideration the combination of blue and blue green roof that was to be installed as part of the plan to better conserve water, boost biodiversity, clean the air, and improve the microclimate of The Acre.  

Following the calculations, however, complications arose due to the concurrent installation of solar equipment and privacy screening on the same areas of the rooftop where ACO’s RoofBloxx were to be installed. 

Unexpected obstructions 

Due to limited on-site storage space and multiple aspects of the renovation being carried out simultaneously, only a small portion of the required ACO RoofBloxx could be delivered at a time. ACO communicated closely with Lendlease’s site managers and adapted its usual delivery process to ensure product was at The Acre at the time it was needed. This flexibility was made possible due to ACO’s facility in Shefford, which houses products ready for shipping in cases when short lead-times or sudden changes are a factor. 

The main hurdle ACO and contractors from MAC Roofing had to contend with was the unexpected appearance of struts installed directly onto the rooftop to support other building services. These were in place to hold PV panels and screens to block plant equipment from public view to improve The Acre’s visual aesthetic. The schematic for the ACO RoofBloxx installation had been created before these struts were known to ACO. MAC Roofing discovered their placement when they arrived to carry out the drainage installation. Because of this, designs had to be adapted quickly, while ensuring that the finished product would provide the attenuation needed and prevent any leaks. 

Cutting carefully 

For each of the 100+ struts MAC had to work around, pitch pockets had to be put in, the insulation had to be altered, and ACO RoofBloxx units cut to fit the space available. MAC contractors measured the obstruction, cut the units to the new size by hand, then taped and sealed each part individually without risking any unwanted water ingress. With each cut that had to be made, the potential for leaks increased, so it was vital that the unplanned adaptations were completed to a high standard across all seven sections of roof. 

Once the ACO RoofBloxx units were in place, other parts of the renovation meant that pipes and pedestals were placed directly on to the ACO RoofBloxx which was also an unforeseen change. ACO created a new set of structural load calculations to ensure that the components combined with the gravel would not compromise the ACO RoofBloxx’ performance or any aspect of building safety.  

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