Waterproofing Your Green Podium Garden

Green podium gardens offer urban dwellers an opportunity to experience green living in the hustle and bustle of inner city living. Often set above the podium in front of the residential tower, it’s essential that podiums are properly waterproofed to avoid adverse impact on the day to day operations of the building. In this article, we look at how you can ensure your green podium garden is properly waterproofed.

Good for people

With more and more people living in urban environments, city planners, designers and architects are on the lookout for ways to increase green space. Green podium gardens are a type of rooftop garden that utilises the space above the podium in residential and commercial structures, offering both public and private escapes from the urban environment.

Good for the environment

As urban and industrial environments continue to spread, we threaten the habitats of native flora and fauna. Rooftop and podium green spaces don’t just help people, they also help flora and fauna. For example, in Toronto, Canada, the Pollinator Protection Strategy Initiative cites rooftop gardens as one way to help protect bee populations that are increasingly disparate. Just one of many reasons why rooftop and podium gardens are becoming increasingly popular.

Design and planning

Essential to a functional, watertight green podium is proper design and planning, so that waterproofing elements are correctly deployed during build. Re-waterproofing a poorly designed or build green podium garden can be costly to both the garden and to other areas within the structure. When designing a green podium garden, here are some considerations to take into account:

• What is the purpose of the green podium garden?
• What is expected to be included?
• Is the designated area suitable?
• What risks are associated with placing the green podium on this site?
• Who are the stakeholders in its construction?
• Who will take ownership of the project?
• What other personnel need to be involved?

For more information, read this article on designing your own rooftop or balcony garden.

Suitability

Is the site suitable for a green roof podium? Consider the following:

• The load capacity of the site
• Weather considerations (average seasonal temperatures, sunlight and rainfall)
• Shade from sunlight and rain from adjacent structures
• Access to podium for residents and for maintenance and staff

Plant and vegetation

The types of greenery present on any podium garden depends on a number of factors, which in turn help define the type of waterproofing required for the podium. Not all plants are suitable for all environments, so during planning consider:

• Tolerance of plants to drought, heavy rains, sunlight and other factors
• Depth of substrate required for vegetation
• Do the plants create habitats for fauna

Waterproofing, design and demand

In designing any rooftop green space, there is a tricky balance between waterproofing, desired design and demand placed by the environment and plant life. During the design process, expect to revisit each aspect as competing requirements for each strain the planning process:

• Design must complement waterproofing and demand
• Demand cannot exceed waterproofing capacity and work within the design
• Waterproofing must meet demand within the design

If these three axioms can’t be met, then changes should be made to the plan.

Water runoff

Typically, a green roof structure like a podium garden will reduce water runoff by about 50%. However, this is contingent on the capacity for the waterproofing system to quickly shed water from the surface. Without sufficient irrigation and water storage, vegetation will flounder.

Root resistance of waterproofing

All waterproofing solutions should be robust enough to restrict root damage. This means that root systems can’t penetrate the waterproofing system or damage irrigation components. Ensure your waterproofing certification is FLL tested and certified.

Standing water

Any rooftop garden is going to gather standing water after rain. Rooftop irrigation is essential, as is water storage depending on the environment. Waterproofing should also not be affected by standing water. Membranes should both be resistant to standing water and play a part in triage of standing water to irrigation and storage.

Hiring a certified applicator

Rooftop waterproofing membrane systems should only be installed by certified contractors. For example, the Wolfin membrane system requires applicators to undergo extensive certification and accreditation process. This ensures that the waterproofing system is installed correctly. Beyond installation of the waterproof membrane and irrigation system, you should expect the following to take place:

• Inspection and signoff of the membrane system by the accrediting organisation
• Technical input from the applicator where appropriate
• Single point of warranty on labour and materials
• Controlled detailing work

If your waterproofing system does not deliver the full package, you may want to consider Projex for your next build.