How Much Does a Fibreglass Roof Cost
A good average to work to would be between £70-£90 per square metre for a basic fibreglass roof without any additional repairs or upgrading to the roof structure and no insulation. For a warm deck roof at the other end of the spectrum, expect to pay nearly double this at £140 per square metre.
Last Updated: October 2022
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Fibreglass roofing is also called GRP flat roof – GRP stands for Glass Reinforced Polyester - and this is one of the most popular flat roofing materials in the UK.
GRP is made of plastic which is strengthened using fine glass fibres and has other uses apart from keeping flat roofs watertight including water tanks, lorries, boats and ponds. GRP or fibreglass is a simple and safe product which is easy to work with and gives a long-standing superior finish.
How much does it cost?
GRP is at the upper end of the cost spectrum when it comes to looking at products to refurbish or replace an existing flat roof. However, it has one of the longest lifespans of all the products in this market in terms of weather resistance and longevity and it is pretty much maintenance-free. It also has an attractive laminated finish so really does look the part too. How much you will need to spend on a new fibreglass roof will depend on a number of factors:-
- Do you also need to bear in mind cost to repair your roof and undertake any structural repairs to the roof frame before the GRP is laid?
- Do you need any adjustments to or even renewal of the rainwater goods so guttering and downpipes?
What is the advantage of a fibreglass roof over other roofing materials:-
- Fibreglass has one of the most impressive lifespans out of all the roofing materials available for flat roofs
- It is more durable than a traditional felt system
- It is easier and safer to install than some of the older style materials which involve working with an open flame
- GRP is very flexible which makes it ideal for all sorts of different styles or roof designs
- There are no joints or seams on the main roof and no taping reducing the locations where water can penetrate, in fact, it so waterproof, it is often used for boats and yachts to keep them watertight and seaworthy
- The top coat finish is highly weather resistant to snow, ice, frost and storms and doesn’t lose its form or function
- Fibreglass is unaffected by UV light
- It is fire resistant
- Fibreglass is strong enough to support footfall so is an ideal material for a roof terrace
- Maintenance of fibreglass roofs is minimal, just a quick brush over and hose down now and again and that’s job done. Read our pages on roof moss removal costs and the cost of roof cleaning and coating to learn more about keeping your roof looking new.
- The top coat resin is very aesthetically pleasing and lacks the rubberised look of some other roofing products. This top coat can be purchased in a variety of different colours and shades
Can you fit a fibreglass roof on top of an old felt roof?
This is not recommended. A flat, dry and solid surface is the pre-requisite before laying a GRP roof, usually wood at a depth of 18mm is ideal and you can also lay it on concrete providing the concrete is very dry and has a relatively fine finish. If you don’t have a flat finish then when the GRP is applied, it will fill in the dips and depressions and then create pools when it rains.
Does water eventually damage the fibreglass?
Fibreglass is water-resistant and waterproof, a fact that can save you money for leaky roof repair costs. However, when you apply the roof, you will need a dry day as it cannot be laid in rainy weather. It will be dry and resistant to rain within one hour.
Can I walk on the roof?
Fibreglass roofing is designed to bear footfall but it can be extremely slippery so if you do intend to walk on it regularly then make sure you add an anti-slip coating as a final layer. Sometimes, two layers are installed if the intention is to use the flat roof as a terrace.
Why does the guarantee impact on the cost?
If you want a longer guarantee then the contractor will need to install an additional coating of resin in order to warranty the roof for 30 years. This extra layer will cost between £10 and £15 per square metre. It is possible to stretch to a 40-year guarantee but that simply requires even more work so the final bill will increase accordingly although many householders feel this is worth it.
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