Types of waterproofing membranes for roof gardens | Mapei Singapore

 August 26, 2020. 11:04 AM

In cities, we are seeing more roofs being transformed into multi-functional spaces to accommodate roof gardens and urban farming. This could possibly be attributed to the increasingly widespread attention given 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: it lowers temperature inside the building which reduces the urban heat island effect, absorbs carbon dioxide, reduces the level of fine dust, and improves the quality of air, while beautifying the building and environment.

Roofs are exposed to external elements such as rain, temperature changes, water ponding and other impacts depending on what the roofs are intended for. Waterproofing is therefore one of the most important aspects in a project: protecting the building shell, stopping water from getting inside and ensuring durability of the building. The selection of waterproofing membranes depends 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 requires waterproofing protection as well as resistance 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
  • Resistance to immersion
  • Resistance to chemicals
  • 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, hence, there is no need for reinforcement. The excellent crack-bridging properties, even at low temperatures, exceptional elasticity of more than 350%, and high resistance to chemicals means that they may be used for a variety of applications, to provide a waterproofing layer that is strong, elastic and seamless.

Types of waterproofing membranes for roof gardens


  • Use synthetic preformed waterproofing membrane. This type of waterproofing membrane comes in flexible polyolefin FPO that is  reinforced with glass mat and sometimes fleece-backed. The Mapeplan series: Mapeplan B, Mapeplan T B, Mapeplan TA F are certified to resist 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 behaviour 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, which is made of distilled bitumen-based compound that is modified with polypropylene, and with continuously threaded non-woven polyester fabric that is  reinforced with longitudinal glass fibre. It is also rotproof, resistant to puncture and has excellent mechanical characteristics in terms of elongation and tensile strength. Antiradice PE is applied by torch-on after a bituminous primer has been applied.

Types of waterproofing membranes for roof gardens

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 quality standards (in Mapei’s case, our products are EN 13948 and FLL certified). 

Write to us for any questions at mapeimktgsg@mapei.com.sg.

Products mentioned in the article

Mapeplan® T Af is a synthetic roofing waterproofing membrane in flexible polyolefin FPO produced in one multi-extrusion coating process,…
Mapeplan® B is a synthetic roofing waterproofing membrane in PVC-P produced in one multiextrusion coating process, with high quality raw…
Two-component, solvent-free, pure polyurea membrane applied by spray with a high-pressure, bi-mixer type pump, to form waterproof coatings…

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