A guide to GRP: Glass Reinforced Plastic

Glass Reinforced Plastic – heard of it? If not, you’re probably not alone. The material used for a huge range of applications can be found almost anywhere, but it is often overlooked by many. At HR Kiln, we specialise in producing and manufacturing bespoke GRP services, and today we’re sharing with you everything you need to know about Glass Reinforced Plastic, and why it may be time to make the switch from conventional materials.

What does GRP mean?

If you’re not part of the construction, engineering, or maintenance industry, then you may have never come across the term GRP before. GRP, or Glass Reinforced Plastic, however, is used in a huge variety of applications and serves as a reliable, hard-wearing, and sturdy material for use in construction especially.

So, although you may never have heard of it, you will almost certainly have come across structures or equipment that have been made using it.

Sometimes also referred to as fibreglass, composite glass or FRP, Glass Reinforced Plastic has proven extremely popular in recent years as a more beneficial, and affordable alternative to more traditional thermoplastics.

Keep reading to find out why!

Why use GRP?

GRP is a fibre reinforced polymer, otherwise known as a composite material. It is made from plastic which has been reinforced using fine fibers made from glass. In essence, it is this unique construction that makes Glass Reinforced Plastic so appealing in engineering, construction and maintenance.

Thanks to the ultra-lightweight nature of GRP, and the fact that it can withstand hazardous conditions with ease makes it a go-to solution in areas that may pose a risk. For a clearer picture, let’s take a look at some of the key reasons why GRP has sky-rocketed in popularity in recent years:


GRP is notoriously light. But why is this a benefit? Well, despite how little it weighs, GRP applications remain just as strong, in some cases stronger, than more traditional man load-bearing structures such as steel and aluminium. Not only does this make GRP easier to work with and move where necessary, but it also makes it much cheaper to install.

Resistant to corrosion

Most structures and equipment that are made from Glass Reinforced Plastic are for outdoor applications. A huge reason for this is that GRP is highly resistant to corrosion, meaning it can weather all types of climates. In fact, there are very few alternatives to GRP that can withstand particular service environments, making them a superior option in most sectors.


On most building or construction sites, particularly where electricity is in use, non-conductive structures and equipment are of paramount importance for the health and safety of workers. This means that GRP has become highly popular across a range of projects and is almost always found where electrical risks are high, such as on railways.


Perhaps one of the key benefits to GRP is how affordable it is. Of course, there are other non-corrosive materials out there that are high performing, such as titanium, however, these often come with a large price tag too. GRP offers all the practicality, at a fraction of the cost making it highly economical.

It may sound too good to be true – but bespoke Glass Reinforced Plastic really can serve as a multi-functional, affordable and safe alternative for those looking to increase productivity in the workplace, without compromising on health and safety.

What is the difference between GRP and FRP?

GRP and FRP are almost always discussed interchangeably, so you might be surprised to know that there are crucial differences between the two!

FRP stands for Fibre Reinforced Polymers, and are made from fibres, and polymer matrix. FRPs are ideal in a wide range of industries including, mechanical, civil, biomedical, marine and many more thanks to their ability to achieve high engineering requirements.

The fibres used in GRP vary, and can include E-glass, quartz, carbon and graphite – to name a few. This composite of fibres and polymer matrix can have varying properties, depending on the type of fibres used.

GRP is often referred to as fibreglass, so it’s no big surprise that GRP and FRP are often confused as being the same thing. The main difference between the two, however, is the way they are made. Both a compound material, but FRP can be made from other materials (other than glass) whereas GRP always uses the same materials and is in fact classed as a form of FRP.

So, although Glass Reinforced Plastics are a type of FRP, not all FRP’s are made using fibreglass.

How do you make GRP?

GRP, or fibreglass, is a man-made material. In order to achieve the various properties that have made it so popular, there is a certain process which must be followed.

The glass aspect of GRP usually combines materials such as limestone and silica sand, although there are usually other ingredients included also. This mixture is heated over a steady period to ensure the end result if smooth, robust and safe for use.

This heated material is then passed through brushing machines, which results in a material that can easily be made into glass fibreglass strands. It is from here that the fibreglass is combined with the plastic and moulded into the shape of the structure, or equipment that it will form.

Is GRP waterproof?

Glass Reinforced Plastic is used heavily in construction because it is deemed a superior alternative when it comes to safety. It is for this reason that we so often see GRP being used in anti-slip equipment such as handrails, stairs and ladders. This is thanks to its waterproof properties.

Whether it’s roofing, boats, wheelchair or disabled accessibility or construction sites, anywhere that requires a safe and sturdy outdoor platform will usually rely upon GRP.

What are the disadvantages of GRP?

Although GRP offers a vast selection of benefits, and is typically the preferred option in construction and engineering, there are of course certain disadvantages that you should be aware of before making your final decision.

The two key negatives to using GRP are:

– Poor rigidity and stiffness

– Can only be applied in temperatures below 300-degrees Celsius

Although for many applications, the benefits far outweigh the negatives, it is still important to bear these things in mind.

Most common places to find GRP

Due to its adaptability and low-cost, GRP can actually be found in a wide range of applications, across a variety of sectors. Most commonly, GRP is found in the making of:

  • Pipes and drain coverings
  • Valve bodies
  • Storage containers
  • Automotive bodies
  • Construction – i.e. ladders, walkways, grates
  • Anti-slip protection on flooring
  • Electronic enclosures
  • Safety rails
  • Safety fencing
  • Wind turbine blades
  • Sporting equipment

This is, of course, just a small window into how versatile GRP actually is, and why it has ultimately become one of the most popular materials across different manufacturing industries.

Do you require bespoke GRP?

Here at HR Kiln, we have been specialising in Glass Reinforced Plastic for a number of years. Working across a wide range of sectors, we can provide GRP equipment and structures to suit your specific requirements – so why not get in touch? Our team are on hand to help!

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