Cookies disclaimer

I agree Our site saves small pieces of text information (cookies) on your device in order to deliver better content and for statistical purposes. You can disable the usage of cookies by changing the settings of your browser. By browsing our website without changing the browser settings you grant us permission to store that information on your device.

Disadvantages of Fibreglass Roofing

Glass Reinforced Polyester roofing (GRP), popularly known as fibreglass roofing, has become a common roof coating in the UK. You can attribute this to its durability and cost-effectiveness. A GRP roofing system can be used on residential and commercial properties alike. While it offers good value for money, some disadvantages of fibreglass roofing have emerged, including the following.


Everyone looks for affordability, prioritising roofs within a friendly budget. Unfortunately, GRP roofing is not the cheapest in the market. While its initial cost is relatively high, it does provide value for money in the long term when compared to other roofing materials.

The overall cost of GRP roofing will depend on whether it is a new installation or a repair. You'll pay £70 to £90 per square meter, depending on the location and expert chosen. The average cost per square meter of a fiberglass roof varies with the warranty, where enhanced durability increases the amount. In addition, balconies increase the average price due to the requirement of a top coat.

Installation Of A GRP Roof

The installation process of a GRP flat roof is what determines the long term success, as if this is not carried out properly various disadvantages can occur. As quality of contractor is vital here it is strongly advised to do your research and choose a reputable roofing contractor. Even though this may rise initial cost, it will reduce the probability of the common fibreglass roof problems in the long run. A key point here is to choose a contractor approved by the system you are using.

GRP Roof Cracking

GRP is a roofing material which is susceptible to cracks. The reason fibreglass roofs crack is the resin used does not offer as much flexibility. It is quite a rigid system. In the UK, the problem here is drastic changes in temperatures throughout the year which will put this system under strain. Liquid roofing systems stand up to thermal movement much more effectively than GRP roofs.

Causes of Cracks on Fibreglass Roofs

Extreme temperatures can significantly disorient the structure of this fibreglass roof. For instance, increased temperatures will expand the roof, while lower temperatures make it contract. The repetition of these movements could readily damage a GRP roof, resulting in flakes and cracks.

Fixing Cracks on Fibreglass Roofs

A pu liquid roof sealant is the best choice for fibreglass roof crack repair. The reason for this is the system has more elasticity than the GRP roof below. This is what has made liquid coatins so popular for both residential and commercial roof repair. Highly elastic liquid coatings prevent a repair patch from being rather rigid on top of a rigid roof system which has already cracked. The way to carry out this repair is clean the damaged area, use an abrasive to remove the GRP coating. Fill any cracks with a pu sealant. Prime the area, then apply the liquid roof coating.


Pinholes could also emerge in fibreglass roofs. They result from the insufficient coating during installation. Essentially, this means the roof was not installed properly. Fortunately, you can fix them by applying a liquid coating over the damaged area. Although this sounds simple, in practice it is best to use a professional roofing contractor, who can carry out a peel test to ensure adhesion is good.

Ponding on the Fibreglass Roof

Ponding is the accumulation of water or unwanted water pooling on a flat roof. This problem is common in fibreglass roofs, causing leaks and holes. It accelerates the deterioration of the roof, exposing you to unwanted repair and replacement expenses. For this reason, you must arrest the issue on time.

Discolouration From Ponding

Ponding causes discolouration on fibreglass roofs. This colour change makes your roof less appealing, compromising property value in the long run.

At the same time, fibreglass roofs tend to lose colour without water ponding. They turn dull and unappealing after a few years. However, without water ponding, the process is much slower. Any roof can always be rejuvenated and have its lifespan extended by having a liquid overlay. A liquid overlay encapsulates the entire roof with a liquid membrane. As a GRP roofing system reaches the end of its service life this is often a cheaper alternative than a full roof replacement.

How to Handle Fibreglass Ponding

Fibreglass roof ponding is easy to notice. Ensure you reach out to a professional to rectify this problem as soon as you see it. This specialist will help fix the problem by boarding the roof with reliable firings, then these firings will be waterproofed with a liquid system. In such instances, an extra layer of GRP coating will not suffice. An instant response will help minimize the damage to your roof, guaranteeing longevity and value for your money.

Damaged Guttering

Functional guttering will help ensure the roof remains appealing and in shape. Unfortunately, fibreglass is a flat roof that will is susceptible to this issue. This problem requires you to frequently clean and repair the gutter, avoiding blockage and damage.

Remove the leaves and debris on your roof from time to time. A buildup of these materials could compromise the functionality of your gutter. You can rely on professionals for regular inspection and maintenance, guaranteeing better results in the long run. This professional could also help evaluate whether you need a new gutter system.


Fibreglass roofing is associated with noise. This problem will likely become bigger during specific weather conditions.

Causes of Noisy Fibreglass Roofing

The leading cause of noise caused by fibreglass roofing is the weather. Temperature changes cause the fibreglass material to expand or contract, producing noise. This thermal expansion causes intermittent contraction and expansion, resulting in noise, cracks, and flakes on your roof.

Noise is significantly common during the summer. You can attribute this to the extensive temperature changes during the period. The fibreglass sheets will rub against wood as they expand or contract, resulting in noise.

How to Solve the Noise Issue

Various approaches suffice if you want to solve the noise problem. Thermal expansion is natural, meaning you expect it after roof installation. However, installing unique expansion joints will help avoid this problem in the long run. These joints allow the sheets or panels to expand without scratching against the wood, reducing the amount of noise produced.

Alternatives to Prevent Fibreglass Roof Noise

You can also consider an alternative to fibreglass material for your roof to avoid noise. Fibreglass relies on a rigid system which makes it struggle with thermal expansion. You can consider liquid roofing in its place, where Pu liquid will be an excellent choice. You can attribute this to its flexibility and easy adaptation to temperature changes. Just like you should choose a reputable GRP roofing contractor you should also choose a reputable liquid roofing contractor. The extra cost will be more than paid back by a prolonged service life.

Although fibreglass roofing is an excellent flat roofing system. There is a potential for some flaws. This can be minimised through using a professional reliable roofing contractor to install your GRP flat roof.

Do You Need Help With A Fibreglass Flat Roof Problem?

Do you have a problem with fibreglass roofing. Or would you like to know more about superior systems which overcome the disadvantages of fibreglass roofing? If you would like to talk to an expert about the right system for your roof or would like to know they best way to fix a fibreglass roof problem please get in touch using our contact form or call 01277 503110.