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across the largest trafficked deck area at podium level, Permavoid Podium Deck is able to provide integral drainage as well as water harvesting. Working in this way allows developers and

architects the freedom to design tall buildings with limited space for drainage systems by beginning the water management process at podium level. Utilising a shallow geocellular drainage system reduces the need for pipework to the underside of the deck, giving more usable space on the deck area and additional room to potentially provide valuable amenities such as car parking or leisure facilities. As well as having the innate strength to cope

with trafficked loads, geocellular systems are often selected due to their 95% void ratio. Tis ensures that the systems are capable of collecting and retaining almost three times more water than a typical aggregate sub-base, providing a vital first stage in the process of water management. With the system able to retain water at podium

level, Podium Deck opens up a number of possibilities for the building owner. Water held within the system is able to be harvested for re-use or irrigation within the deck – making it ideal for clients seeking an environmentally sound drainage water management project – or can be attenuated out in a controlled fashion which is sensitive to the building’s surrounding environment. Podium Deck systems are also able to work

in conjunction with a variety of other water management systems to form a solution tailored to the exact needs of the site. Tis is vital on projects where traditional tank-based attenuation systems simply aren’t possible due to a lack of space, but the rate at which rainwater discharges into local water sources still needs careful consideration so as not to overwhelm drainage systems. Other geocellular systems, such as Polypipe’s

Polystorm, can be specified to sit beneath buildings, car parks or roads to provide an alternative to large tanks beneath ground level. Providing the same 95% void ratio as Permavoid Podium Deck, these systems are able to collect large volumes of rainwater direct from podium level drainage systems and ensure that water is discharged at a suitable rate into the surrounding sewer system. One such project where this

approach was taken was our recent work at a 20 floor student accommodation project in East London. Polypipe was approached

to supply an additional attenuation system after it was discovered that an initially proposed concrete drainage system would not be sufficient to manage the site’s drainage requirements in the event of a ‘1 in 100’ storm event. Working closely with the

consultant, Polypipe supplied a two tiered Permavoid geocellular system at a podium level to collect water run off from the site’s standard gravel roof and discharge

Opposite: A geocellular structure beneath permeable paving can provide an effective form of source control


London is the 15th most water-stressed city in the world, and climate change is predicted to increase the city’s daily water deficit to over 350 million litres a day by 2035. Two UK companies, iiLab and Resurgence, have been working from a world centre of excellence based, the Open Data Institute, founded by the British inventor of the World Wide Web, Sir Tim Berners Lee, to crack one piece of the city water deficit challenge - our lack of data on exactly how much water we use across the range of our domestic water appliances. We just don’t know how much water our showers, dishwashers, and washing machines use every day. And existing water meters measure the water we have used only retrospectively.

By contrast, Open Droplet, is a water -proof sensor that will allow us to measure how much water we use on each of our appliances on a real-time basis. Importantly, it will also allow home users to relate their own household use to that of their local community, and to the water targets of their city. ‘We need to develop a new culture around data and water management in cities as urban water becomes an ever precious commodity,’ says Resurgence, CEO Mark Harvey ‘and we are anticipating major interest from utility companies, given that there is clearly a global market for Open Droplet.‘

For further information go to

into a 30m3 tank made up of Polystorm cells. Attenuating the site at podium level meant

that despite limited space on the ground surrounding the development, which limited the scope for a larger below ground tank, it was still possible to achieve the desired discharge rate of 21l/s whilst making best use of the space. With cities continuing to grow, and more


storm events predicted, providing a considered approach to water management projects like this is going to be increasingly important. As local watercourses make way for buildings, we should ensure that our buildings make space for water.

Adam Turk is Commercial Director at Polypipe and is a member of UKTI’s High Value Opportunities Supervisory Board. For further information go to




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