Due to its durability, water resistance, and versatility, GRP or Fibreglass roofing is a popular choice in the UK for residential and commercial flat roofing. However, one aspect that often surprises new users is the strong odour associated with its installation and curing process. This article explores why GRP roofing using traditional polyester-based resin is so smelly and how to reduce the impact of the odour.

The Chemistry Behind the Smell

The primary reason GRP Roofing emits a strong odour is down to the chemical composition of the materials used in its manufacture. GRP is made by combining a polyester-based resin system with fibreglass reinforcement. The resin requires a catalyst to harden and set into a solid, durable form. This process is known as curing.

Volatile organic compounds (VOCs) are a group of chemicals that have a high vapour pressure at room temperature, which means they easily become vapours or gases. The most common VOC in GRP Roofing is Styrene, a chemical used in the resin whose primary function is to facilitate the application and curing process.

Styrene has a distinct, pungent smell that can be quite overpowering, especially in enclosed spaces. The same polyester based resins that go on your roof are used every day in factories and workshops up and down the country to create a wide range of products from baths and boats to planes, trains and automobiles. The warehouses have to be equipped with special ventilation systems to extract the fumes and the laminators working with these resins will have special masks so they don't breathe in the fumes.

A low styrene emission polyester resin was developed in 1988 to mitigate some of the known hazards of styrene but the VOCs are still there and it's essential to ensure proper preparation during the installation of a polyester-based GRP Roofing system.

Factors Influencing the Intensity of the Odour

A number of different factors can influence the intensity and duration of the odour emitted during a fibreglass roof installation.

Different polyester resins have varying levels of VOC emissions and while it's the standard for everyone to use Low Styrene Emission (LSE) polyester resin you will find low-quality products sometimes labelled as "Standard" or "Low-cost" products which are either reblended or taken from a different industry sector to use in fibreglass roofing which could have higher levels of VOC's.

Higher temperatures that accelerate the resin's curing process can also lead to a more intense release of VOCs over a shorter period. Conversely, lower temperatures can prolong the curing process but may result in a more gradual release of odours.

Mitigating the Odour

While it may be impossible to eliminate the odour, there are a number of things you can do to mitigate it;

Use a Styrene-free system

Opting for a fibreglass roofing system like Fibrecoat which is low-odour and styrene-free will significantly reduce the intensity of the smell and is the perfect solution for working on larger projects such as schools and hospitals where low or zero odour is a requirement.

Seal the Area

Before a tin has even been opened, close and seal all the windows and vents around the property, and inform neighbours to do the same. The smell has been known to linger for up to seven days after the system has been applied.

Timing and Weather Conditions

For sensitive projects near schools or commercial developments, plan the installation for times when weather conditions are optimal. Avoid very hot or humid days, as these can exacerbate the release of VOCs.