New Drainage System Paves the Way

30mm drainage cell Roof gardens are becoming increasingly popular with high rise developers following the release of a new drainage system.

It was designed to solve problems such as clogging and water seepage and as much as $100,000 extra is being paid for penthouses which open onto these gardens.

Humberto Urriola, a Sydney landscape architect who is the inventor of a new system - the Atlantis Drainage Cell.

"A recently completed waterfront project, where the penthouse would normally have sold for $600,00 fetched $750,000 - it had a rooftop garden.

"The total cost of the drainage cell and landscaping was only $30,000 so it was a very profitable decision to put them in," Urriola said. A less common, but even more remarkable increase in price was achieved in the eastern suburbs where a penthouse was valued at $1.5 million without gardens, and later, when the gardens were completed, sold for $2.8 million.

According to Urriola most buildings have unused and unattractive concrete areas on top which, with Drainage Cell, could be landscaped into beautiful gardens without the problems usually encountered when traditional drainage methods are used. The Atlantis Drainage Cell has affected landscaping, not only of rooftops, but also of ground level gardens. It comes in rigid 30cm square tiles capable of withstanding such pressure that it can be used everywhere that drainage is required.

"Because it is lightweight and each tile is simply laid edge to edge before being overlaid with Geofabric, the drainage cell can be installed with minimal labour and cartage costs.

"Because it is so strong, the area can be backfilled in the usual way with a Bobcat or grader," he said.

The Mirvac Group used the Atlantis Drainage Cell on two of its recent projects - Harbour Lights in Milson's Point, a 13 storey residential building, and Essex House, a 28-unit project at Killara.

At Harbour Lights, Drainage Cell has been used under the roof garden, and at the Essex House project, it has been extensively used under the gardens of each of the units which are terraced back up a slope. Geoff Davey, marketing manager of Mirvac, said the new drainage offered many advantages, the biggest in his opinion being that it would not clog like other systems, so water would continue to drain away effectively throughout the life of the building.

"In any situation where you are laying a garden over a concrete slab the garden is reliant for its life on a fairly thin layer of soil that has to be drained. This new system ensures that the drainage will continue to work effectively," Davey said.

"A lot of plants don't take to damp conditions, so the new drainage cell allows us to create better gardens with a more comprehensive range of plants," he said.

He believes many developers are more likely to build gardens now the drainage cell is available.

"In the past decisions were sometimes reluctantly made to pave rather than build gardens on concrete slabs because of drainage problems which have to be faced in the future."

He said because it's light weight the Drainage Cell allowed small gardens to be built on hoods over doorways thus providing a pleasant outlook for thos above and in a variety of horizontal and vertical situations ultimately adding to the value of the property.