Green Roofs designs: Solutions with liquid-applied waterproofing membranes

Greenery and green spaces boost health and wellbeing. Numerous studies have shown that they can help reduce stress, improve cardiovascular health and increase focus and productivity. Even having sight of greenery through a window creates positive effects through biophilia – our natural love of nature. In cities, green areas deliver further health benefits, helping to reduce air pollution, noise and heat island effects.

Yet, with almost half of the European population living in flats - 46.1% in 2019 according to Eurostat – our contact with nature has become less frequent. Stress levels, physical inactivity and obesity have increased dramatically.

The Covid-19 pandemic, which spread around the world from 2020, exacerbated these problems as people were urged to stay at home and public parks were closed. And it underlined the importance of access to outdoor space and greenery and to get fresh air, soak up natural light, sunbathe, but also to work, make calls or engage in any other activity, including socially distant conversations with neighbours.

The pandemic proved how much we need green roofs and spaces in today’s urban environments.

A green roof incorporates a layer of vegetation on top of a flat or slightly sloping roof. As a minimum, it consists of a waterproofing layer, preferably with root resistance properties (if not a root repellent system), a drainage layer, a geotextile filter, a planting medium, and plants. A thermal insulation layer will be necessary and, in the case of liquid applied waterproofing membranes, this will normally be installed above the membrane (known as an ‘inverted roof’).

Robust and durable roof waterproofing membranes are a minimum requirement in all roof waterproofing, but especially for flat roofs. In the case of green roofs, additional precautions need to be taken as, once the roof is completed, the waterproofing system will be constantly exposed to moisture, chemicals and roots and any leaks that occurred would be very difficult and labour-intensive to locate and repair.

A green roof requires a high standard of workmanship during its installation. Because it needs regular maintenance over the lifetime of the roof, there is a higher risk of damaging the membrane if it has not been properly installed with a build-up that protects it from mechanical damage.

The use of roofs as recreational areas can lead to designs with multiple layouts combining trafficked and relaxation areas with landscaped areas or even swimming pools. The application of the waterproofing system should always be designed to provide robust and effective resolution of any necessary construction details, such as interfaces with drains, pipes or other installations.

MasterSeal Roof systems – remove seams, remove risks

Homes, parking lots, airport terminals, industrial plants, offices, warehouses, churches, shopping malls, all types of buildings need an external "skin" to protect both the structure and its contents, from the elements. As part of the building envelope, the roof needs a durable waterproofing system, adapted to suit the temperature and environmental changes as well as to protect against environmental threats such as pollution and acid rain.

MasterSeal Roof systems are based on a fully bonded, seamless waterproofing membrane, avoiding welds and seams that are typically the weak spots in any waterproofing system. They form easily watertight connections with drains, vertical elements, roof vents, rooflights or anchors.

In many cases, leaking roofs can be repaired with a MasterSeal membrane without removing the old waterproofing layer. This offers clear time and cost savings, including cutting the cost to dispose of the old membrane.

Advantages of liquid waterproofing membranes

• Unlimited surfaces: liquid systems allow the application of a continuous membrane on large surfaces without limitations, seams, overlaps and bonding procedures.
• Applicable to shaped substrates: spray-applied systems can be sprayed on horizontal, vertical, and sloped surfaces.
• Easy detailing: liquid systems allow easy detailing, creating a continuous layer membrane around roof elements without the need for seams, prefabricated moulded parts, mechanical fixings or additional flashings.
• Root resistance: membranes with built-in root resistance prevent aggressive roots from breaking and penetrating the waterproofing system.
• High chemical resistance against fertilisers, herbicides and other plant growth substances.
• For new and refurbished roofs: thanks to a complete primer toolbox, MasterSeal Roof systems can be installed on most substrates, even on existing roofs without the need to remove previous waterproofing systems.
• Lightweight: adding minimal dead load on the roofs, below 5 kg/m²
• Quick installation: an application using spraying equipment can achieve high application rates.
• Rapid hardening: successive parts of the system can be installed without delays or downtimes.
• Long service life: MasterSeal systems can be applied on exposed surfaces which experience a high range of temperatures, weathering, and rain conditions. Long-term durability in these conditions without stiffening, softening or UV-related damage provides a service life up to 25 years.

Rooftops and green spaces: a growing trend

Worldwide, the use of green roofs is increasing to reduce environmental damage and improve quality of life, reducing the impact of dense development in urban areas.

In some property markets, additional ‘green’ or sustainable features are desirable, because corporate tenants and their shareholders are looking for buildings that demonstrate their commitment to the environment. However, for some investors and developers, the increased costs for the installation and maintenance of green roofs can make them a less attractive proposition.

To increase their uptake, some governments and municipalities are promoting and subsidizing the installation of green roofs. For instance, there are programs in New York, Hamburg, Barcelona and Hong Kong. In London, planning regulations have been changed to mandate a certain amount of green space, depending on the type and size of development.

The characteristics of MasterSeal Roof systems - seamless, root resistant and high durability – mean that building owners can ensure high long-term performance and minimal maintenance costs for green roofs which will also encourage uptake.

Sources:

• James, P., Banay, R.F., Hart, J.E. et al. A Review of the Health Benefits of Greenness. Curr Epidemiol Rep 2, 131–142 (2015). Available at: https://doi.org/10.1007/s40471-015-0043-7
• Untapped New York. “The revival of rooftop culture during the coronavirus pandemic in NYC”. (online) Available at: https://untappedcities.com/2020/07/03/the-revival-of-rooftop-culture-during-the-coronavirus-pandemic-in-nyc/
• Tiago Liberalessoa, Carlos Oliveira Cruz, Cristina Matos Silva, Maria Manso. “Green infrastructure and public policies: An international review of green roofs and green walls incentives.” Land Use policy 96 (2020) 104693.
• Ecología práctica. ““Et posem verda”: nuevo proyecto para la creación de terrazas verdes en Barcelona”. (online) Available at: https://www.terra.org/categorias/articulos/et-posem-verda-nuevo-proyecto-para-la-creacion-de-terrazas-verdes-en-barcelona
• Mayor of London. Urban greening. (online) Available at: https://www.london.gov.uk/what-we-do/environment/parks-green-spaces-and-biodiversity/urban-greening