In cities, we are seeing more roofs being transformed into multi-functional spaces to accommodate roof garden and urban farming. It could possibly be attributed to the increasingly widespread attention to eco-sustainable buildings, along with the tendency to reclaim “green” areas within urban surroundings. It is obvious that a “garden roof” or “green” roof spells numerous benefits: lowers temperature inside building which reduces the urban heat island effect, absorbs carbon dioxide, reduces the level of fine dust and improves the quality of air, at the same time, beautifying the building and environment.

Roofs are exposed to external elements such as rain, temperature changes, water ponding and more depending on what the roofs are intended for. Waterproofing is one of the most important aspect in a project: protecting the building shell, stopping water from getting inside and ensuring durability of the building. The selection of waterproofing membranes depend on the function of the roof and environment conditions. Each type of covering requires specific attention, depending on the slope of the surface and the method used to lay waterproofing materials to prevent infiltration. For roofs that are converted to gardens, it require not just waterproofing protection but have to be resistant to root penetration.

Requirements for waterproofing a roof garden

The suitable waterproofing system in this context will require:

• Resistance to root penetration and micro-biological attack
• Resistance to loads and atmospheric agents
• Immersion-resistant
• Chemical-resistant
• Good mechanical properties – tensile strength, elongation and tear resistance

Types of waterproofing membranes suitable for roof garden

• Use polyurea waterproofing membrane. The benefits of polyurea membrane such as Purtop 1000 (two-component, solvent-free, pure polyurea waterproofing membrane) is that it is spray applied, therefore making installation easy. It has excellent adhesion to numerous types of substrate. Waterproofing application is immediate in just less than 4 minutes and can be open to foot traffic after 20 minutes. Furthermore, it has very high tensile strength of 25 N/mm². There is no need for reinforcement. The excellent crack-bridging properties, including at low temperatures, exceptional elasticity of more than 350% and high resistance to chemicals means they may be used for a variety of applications, to ensure a waterproofing layer that is strong, elastic and seamless.

• Use synthetic preformed waterproofing membrane. This type of waterproofing membrane come in flexible polyolefin FPO reinforced with glass mat and sometimes fleece-backed. The Mapeplan series: Mapeplan B, Mapeplan T B, Mapeplan TA F are certified to be resistant to root penetration, microorganisms and UV rays. Take for example, Mapeplan T B membrane has excellent dimensional stability, is watertight and resistant to impact and static load. It has a high tensile strength of ≥ 9 N/mm² and tear resistance of ≥ 150 N.

• Use plastomeric waterproofing membrane. Plastomeric membrane is a combination of plastic and elastic behavior with low recovery after stretching. It is often used with reinforcement for dimensional stability, increased tensile strength and elastic recovery. One such example is Antiradice PE, made of distilled bitumen-based compound modified with polypropylene and continuous thread non-woven polyester fabric reinforced with longitudinal glass fibre. It is rotproof, resistant to puncture and has excellent mechanical characteristics in terms of elonogation and tensile strength. Antiradice PE is applied by torch-on after a bituminous primer has been applied.

Before deciding on the waterproofing materials, it is recommended to consult the supplier or Technical consultant on your requirements. You can also request for a Test report to show that the selected waterproofing materials complies with the standards (in Mapei’s case, our products are EN 13948 and FLL certified). 

Contact Mapei Singapore for your projects.

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About Mapei:

Founded in Milan since 1937, Mapei is today a world leading producer of adhesives and complementary products for the laying of all types of floor, wall and coating materials. Mapei’s specialty lies in products for ceramics and stone materials, among other product lines. Mapei’s tile adhesives are certified according to international standards and are SGBC certified in Singapore. Experience proven by numerous notable projects worldwide.