The GRP Installation Process Explained

July 3, 2023

The GRP Installation Process Explained

GRP (glass-reinforced plastic) is a composite material, made from a resin that’s combined with CSM (glass fibre chopped strand matting). GRP is a popular roofing material used by many. GRP is widely used across the globe on various projects by both builders and roofing contractors.

In terms of protection, GRP roof installation is fully waterproof and offers reliability and longevity. As well as being a quality roofing component to use with an array of key benefits, GRP is chemically resistant and durable. Many industries favour GRP, including construction, marine and aerospace to name a few.

GRP is typically used across flat roof installations, acting as the ideal system. Fibreglass flat roofs are one of the most common types of roof choices to go for, and liquid roof coating applications are widely used. Compared to more traditional roofing materials, GRP roofing systems come with plenty of advantages, acting as one of the toughest solutions on the market today. To find out about the GRP installation process, read on.


What is GRP?

What is GRP? GRP is a type of material used widely across the globe. It can be difficult trying to find a hard-wearing solution to suit your roof structure, but not when GRP systems are available. Offering many conveniences, GRP is relatively easy to install if you’re a trained professional and requires minimal upkeep.

Understanding the importance of protecting your roof is key. Having a system in place that’s able to withstand harsh weather conditions such as rain, wind and intense sun is essential – especially in the UK. The capacities that GRP offers continue to stand the test of time, proving its excellence each time it’s used.

GRP acts differently compared to conventional thermoplastics. Due to its plethora of uses for a wide range of applications, GRP is considered a firm favourite within the industry. Although GRP is a strong material that provides a fully waterproof seal, the solution is extremely lightweight.


What is GRP Made of?

GRP is made from fibres, which are ultimately made from small strands of glass. These specific fibres used to create GRP are very fine and woven together to create a flexible, robust fabric. One of the biggest advantages of GRP is its incredible versatility which allows it to mould the shape of any surface it’s applied to – regardless of the shape or curvature.

Roof designs can’t be perfect – there are curves, cracks and tedious spaces to cover. GRP offers a seamless finish, giving your roof a new lease of life and a tidy appearance. The materials used to create GRP provide users with high resistance and long-term wear, which is ideal for flat roof surfaces.


The GRP Installation Process

The installation process for GRP roofing is relatively uncomplicated if done correctly by trained professionals. There are a few simple steps you can take to be able to apply GRP the right way with excellent, seamless results. If the substrate on your flat roof is unfit for laying boards to be applied directly, it’s vital that you remove the surface. Read on for a step-by-step guide for the perfect GRP application.

There are many steps involved during the initial building process of the roof before GRP can be applied. GRP can be applied across various flat surfaces such as balconies, terraces, porches, dormers and bay windows.

It’s essential to use the solution correctly. Make sure to stir your resin thoroughly before applying – this way, any settled styrene and wax can be mixed efficiently. Once mixed, the resin should be added to a liquid catalyst. The measurements per mix should vary depending on the size of the surface you’re covering.

Start by mixing around one to two litres of your solution to laminate the corners and bandage any trims. This process allows you to calculate the curing time and check if the contents are mixed correctly.

Next, you’ll need to overlap the feathered edge of the chopped strand mat on top. You can roll the strand mat out. To create a straight edge, simply use a knife to cut the ends into the corner of the trim.

To lay the corners, position a CSM square to the corner trim, ensuring the bottom edge is on the radius of the trim itself. Fold the corner trim accordingly and use a roller to feather it into place. You can bandage the trims using the same mix of resin and catalyst. Top tip – you don’t have to wait for the corners to cure before moving on to lamination.

The lamination process is relatively streamlined. Dip a medium-sized roller into your catalyst-based resin and add three rollers worth to your boards. Typically, the resin is applied one-third onto the board and two-thirds onto the chopped strand mat.

You can apply the mat directly as you go to the boards already coated with resin. Simply wet the mat in sections using a roller, pushing away from you and back towards you during each run. It’s important to let the resin soak into the mat for at least three minutes.

Before preparing the top coat, roll a paddle roller over your surface continuously. You’ll know if your laminate has been wetted correctly if it’s transparent. Using a sanding pad, sand the corners and bandages, as well as cut any additional overhanging cured mat.

Prior to mixing your topcoat solution, you’ll need to add 2kg of colour pigment for each 20kg of topcoat. If you purchase a pre-pigmented topcoat, you won’t need to add any colouration. Topcoat is usually applied at the measurement of 0.5kg per m2. Add the correct amount of catalyst based on your surface size and stir well.

Using your topcoat mix, cover the remaining laminate using a polyester roller. You only need to coat your laminate with a thin amount of topcoat so that the fibre pattern remains visible. To coat the edge of the trims, you can use the same mix.


Installation Top Tips

It’s essential that you check the weather before installing a GRP system. Dry, mild weather conditions are ideal for GRP installation – if you attempt to lay GRP in wet or windy conditions, the solution simply won’t be able to be laid effectively in the correct way. If the temperature is below 5 degrees Celcius, the resin won’t be able to cure properly, which is a vital stage of the process.

Once the sun sets, not only will you find it difficult to see what you’re doing, but the materials won’t cure adequately if it’s dark outside. Builders and roofing contractors have less time to lay GRP systems in the winter, due to the sun setting earlier than usual.

Checking the temperature of the OSB boards prior to applying GRP isn’t a necessary step that has to be taken, but it could prevent problems from occurring during installation. If the OSB boards are too hot (30 degrees or over), then the wax in the topcoat could melt. This often results in a tacky finish.


GRP Products at Restec

Here at Restec, we provide an array of hard-wearing products that are ideal for both builders and contractors to use. Our products are second to none, proving to be some of the best on the merchant market today.

We manufacture our products with excellence in mind at all times – we understand the importance of having access to a reliable, long-lasting solution that can be applied across various surfaces during construction.

One of our most popular products, GRPROOF 1010 is widely sold up and down the country. GRPROOF 1010 offers an unrivalled performance at an exceptional value. Regardless of whether your project is small or large, simple or complex, you can trust our reliable GRP solutions and GRPROOF 1010 Roof Kits to provide the most seamless, fully waterproof finish.

Engineered for optimal roofing performance, our GRP solution has minimal risks of cracking, delaminating or flaking. This system has outstanding inter-coat adhesion and can achieve BROOF (t4) Fire Rating for unrestricted use. We offer a selection of GRP components, including base resin and top coat.

Correct application is vital when it comes to installing GRP systems. Restec has an array of application tools available to purchase, making that perfect finish even more achievable. If you’d like to find out more about our products, feel free to contact a member of our team here.

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