Bitumen protects buildings

For centuries, bitumen has been recognized as an excellent waterproofing material.

Waterproofing is currently the second largest application for bitumen and accounts for between 10 and 15% of all the bitumen produced in Europe each year – with bitumen mainly used in bitumen membranes that have a wide variety of applications: from weatherproofing roofs and walls, to waterproofing parking garages, ponds, reservoirs, hazardous waste sites, retention ponds and bridges.

The climate is changing and weather patterns are becoming increasingly extreme, which has cost Europe more than €330bn and ended the lives of 85,000 people over the last three decades, according to the European Environment Agency‘s ‘Climate change, impacts and vulnerability in Europe 2016’ report.

Increased rainfall and more stormy weather are being experienced all over Europe. Another peak is expected this Autumn, when bitumen’s waterproofing properties will once again be put to the test.

Bitumen is used to protect numerous prestigious buildings, including the European Parliament building and the Birds Nest Olympic Stadium in Beijing.

Bitumen waterproofing membranes have been available in Europe for over 100 years and are manufactured using high-tech methods to provide effective, environmentally safe protection. They can be installed safely and flexibly, allowing for potential changes in construction even after application, they provide mechanical resistance – which is important for green roofs – and also have a long service life.

Standard bitumen roofing membranes have a typical service life of 30 years and polymer reinforced bituminous membranes are expected, according to BS 8747:2007 ‘Reinforced bitumen membranes (RBMs) for roofing – Guide to selection and specification’, to have a service life in excess of 50 years – that’s roughly two generations!

Bituminous membranes are mainly used to weatherproof flat and low-slope roofs.

Roof gardens, eco-roofing and other green roofs

There are more and more applications for bituminous membranes in sustainable, carbon-neutral residential and commercial buildings, where bitumen’s water-resistance properties are utilised.

In roof gardens, bitumen membranes not only prevent water from draining through the soil into the fabric of the roof, but also act as a physical barrier stopping roots from growing into the roof.

Bitumen membranes are also used in energy-efficient eco-roofing and ‘green’ living roofs, which provide habitats for insects and decrease the sealed area (the ground surface through which rainwater cannot permeate because of urban development) within cities – which leads to up to 75% of rainwater becoming run-off in urban areas.

Historically, turf roofs were common in northern Europe, but decreased in popularity as the industrial revolution progressed. However, in the late 19th century green roofs became popular on multi-storey buildings in Berlin, and this trend continued into the 20th century with more city-centre structures reaping the benefits. Legislation has since been introduced to encourage the installation of green roofs, and by 2001 43% of German cities provided incentives for green roof installation.

Other countries in Europe, such as Switzerland and Austria, also have a long tradition of green roofs. France is beginning to encourage this type of green roofing, and has updated the rules for the design and construction of green roofs and terraces. In Paris, since 2006 it has been compulsory for the wall and / or the roof to be ‘green’ if an application for a building permit does not provide a sufficient vegetated area. Also, 250 acres, approximately 1 square kilometre, of roofs and walls in Paris will be ‘greened’ by 2020 following a charter signed by the Mayor and 33 private companies and public institutions in 2016.

Perhaps you have spotted a building with a green roof recently? Maybe in aerial coverage of a major event, such as the Berlin Marathon or the Tour de France?

The overwhelming majority of modern roofing bitumen products are applied at ambient temperatures in situ. Polymer modified bitumen membranes are now increasingly being installed because of their ease and speed of installation, and are typically either torch applied or fixed using the self-adhesive technique. Pour and Roll is used in some countries and accounts for less than 10% of the complete market.

A few environmental facts about bitumen

Much research has been undertaken regarding bitumen and the environment. Here are a few key facts:

- Bitumen is an inert material that is insoluble in water:

• Bituminous materials are often used to line drinking water reservoirs and in products that line water pipes carrying drinking water.
• Retention ponds are often paved with asphalt to prevent liquid industrial waste material from leaching into the soil.
• Bitumen is used to line and cap hazardous waste sites – preventing rainwater from permeating through the hazardous waste and from leaching into groundwater.

- Soil quality and vegetation are not influenced by bitumen:

• More than 90% of rural paths are built on asphalt foundations, allowing people to spend their free time in and around the local green space, while ensuring that the environmental impact of human contact is minimized.

Bitumen in roofs, walls and floors

As described above, by far the most common application of bitumen in modern buildings is within bituminous roofing membranes, which are increasingly being installed on commercial and residential buildings across Europe - either to provide just a pure waterproofing solution, or to additionally be a base material for roof gardens, eco-roofing or ‘green‘ living roofs.

However, bitumen’s versatility is such that as well as in roofs it is also found within walls and floors, where its water-resistant properties are utilised.