Can You Install Solar Panels On A Fibreglass Roof?
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As the UK continues its transition towards greener energy solutions, more property owners are considering solar panel installations to reduce energy bills and lower carbon emissions. A common question we often get asked is: can you install solar panels on a fibreglass roof?
The short answer is yes, but there are important factors to consider, from structural suitability and waterproofing to mounting systems and long-term durability.
Whether you own a residential home, manage a rental property, or oversee a commercial building, this guide will help you make an informed decision.
Is A Fibreglass Roof Suitable For Solar Panels?
Yes, fibreglass roofs are suitable for solar panels, but suitability depends on the following:
1. Structural Strength & Load-Bearing Capacity
Fibreglass roofs are lightweight, but they must still be assessed for their ability to support the additional weight of a solar PV system.
A standard solar panel weighs around 18-22kg per panel. A full system (including racking, cabling, and inverter) may add significant load per square metre.
Tip: Before proceeding, consult a structural engineer to assess the roof’s load-bearing capacity.
2. Roof Pitch & Orientation
Most fibreglass roofs are flat or low-pitched. Flat roofs can still host solar panels effectively, but mounting systems will need to tilt the panels between 10° to 40° to optimise energy production.
According to the Energy Saving Trust, the ideal roof orientation in the UK is south-facing, with a tilt of around 30° for maximum efficiency.
3. Mounting Systems for Fibreglass Roofs
Unlike tiled or slate roofs where solar panels are typically fixed to rafters, fibreglass roofs require a non-penetrative or ballasted mounting system. These systems avoid drilling into the roof, preserving its waterproof integrity.
Mounting Type | Description | Pros | Cons |
|---|---|---|---|
Ballasted Mount | Uses weighted frames to secure panels | No roof penetration | Heavy, may stress structure |
Adhesive Mount | Uses industrial-grade adhesives | Maintains waterproofing | Needs clean prep, may degrade |
Penetrative Mount | Bolted through fibreglass with waterproof sealing | Very secure | Risk of leaks if not sealed |
If you’re considering going solar, Eco Answers can help.
Our free, easy-to-use Quote Comparison Tool connects you with trusted UK solar suppliers offering competitive quotes tailored to your roof type and energy needs. Simply provide a few details and we’ll match you with MCS-accredited installers.
Pros and Cons of Installing Solar Panels on a Fibreglass Roof
Pros | Cons |
|---|---|
Lightweight roofing material: Fibreglass is lighter than many traditional roofing materials, reducing overall structural load. | Requires specialised mounting: Not all standard mounting systems are suitable, fibreglass may require non-penetrative or ballasted systems to avoid damage. |
Durable and weather-resistant: GRP (Glass Reinforced Plastic) roofs are known for their resistance to rot, corrosion, and extreme weather, making them a stable base for solar arrays. | Risk of cracks or punctures: Improper installation or excessive foot traffic during setup can cause structural damage to the roof. |
Long lifespan: When properly maintained, fibreglass roofs can last up to 30 years or more, aligning well with the average lifespan of solar panels. | Heat expansion: Fibreglass can expand and contract with temperature changes, which may affect long-term mounting integrity if not accounted for. |
Flat and uniform surface: Makes installation easier and allows for adjustable mounting angles with tilt frames. | Potential for limited load-bearing capacity: Not all fibreglass roofs are designed to carry additional weight; structural assessments may be needed. |
Low maintenance: The smooth, seamless surface of fibreglass means fewer potential leak points and easy cleaning. | Planning permission complexities: Especially on flat fibreglass roofs in conservation areas or on listed buildings, planning permission may be required. |
Will Solar Panels Damage A Fibreglass Roof?
When installed properly, solar panels will not damage a fibreglass roof. In fact, they may even prolong the lifespan of the roof by shielding it from UV rays and heavy rain. However, improper installation can cause cracking, leaks, or warping of the roof surface.
This is why it’s critical to use qualified installers familiar with fibreglass roofing materials.
MCS-accredited installers are trained to assess roof types and use suitable mounting systems to avoid damage.
What to Consider Before Installing Solar Panels on Flat Fibreglass Roofs?
Flat fibreglass roofs pose some unique considerations for solar installation, and overlooking any one of them could lead to reduced efficiency, roof damage, or added maintenance costs. Here are the key factors to evaluate:
- Water drainage: Panels must be positioned to avoid disrupting water run-off patterns. Improper positioning can cause pooling, which may degrade the fibreglass and lead to leaks over time.
- Wind uplift: Flat roofs are more exposed to wind. Solar panels need to be anchored with appropriate ballast or wind deflectors to prevent movement or damage in high winds, especially in coastal or elevated regions.
- Access & maintenance: A poorly planned layout can make it difficult to maintain the solar panels or the roof itself. Ensure that the design leaves adequate space for maintenance walkways or access points.
- Roof age and condition: If your fibreglass roof is nearing the end of its lifespan (25–30 years on average), consider re-coating or refurbishing before installing solar panels. It is more cost-effective to carry out roof repairs before solar installation than after.
- Weight distribution: Even though GRP is strong, solar PV systems (especially ballasted systems) can place concentrated loads on specific areas. A structural survey can help determine the best placement for even weight distribution.
- Planning for future upgrades: Consider how the installation might affect future upgrades, such as adding a solar battery or EV charging station. Flat roof systems should be designed to accommodate these technologies with minimal disruption.
- Shading and obstructions: Flat roofs often have vents, air conditioning units, or chimneys. Shadows cast by these structures can reduce energy output. Accurate shading analysis will ensure maximum solar panel efficiency.
- Fire and safety compliance: According to UK building regulations, flat roof systems must meet specific fire safety requirements. Ensure the mounting system and installation approach comply with BS EN 13501-5 standards.
By taking these considerations into account, homeowners and landlords can maximise both the performance and longevity of their solar installation on fibreglass flat roofs.
How Much Does It Cost To Install Solar Panels On A Fibreglass Roof?
Solar panels installation costs can vary significantly based on your roof type, system size, energy requirements, and chosen mounting method.
Fibreglass (GRP) roofs can sometimes require specialised, non-penetrative mounting systems, which may slightly raise the price compared to standard tiled installations.
Key Factors That Affect Cost:
- System Size (kWp) – Larger systems cost more but generate more energy.
- Mounting Method – Ballasted or adhesive systems on fibreglass roofs are often more expensive than standard roof-rail setups.
- Access & Scaffolding – Flat roofs may require extra scaffolding or safety measures during installation.
- Inverter & Battery Options – Upgrades like solar batteries can increase upfront costs but improve long-term savings.
- Installer Expertise – Hiring an MCS-accredited installer familiar with fibreglass roofs may come at a premium but ensures a compliant, leak-free setup.
Estimated Costs of Installing Solar Panels on a Fibreglass Roof (UK 2025)
System Size | Number of Panels | Avg. Installation Cost (Incl. VAT) | Suitable for | Notes |
|---|---|---|---|---|
2 kWp | 5–6 panels | £4,500 – £5,000 | Small homes/flats | Minimal roof space needed; lower output |
3–4 kWp | 8–10 panels | £5,500 – £7,000 | Semi-detached homes | Most common UK install size |
5–6 kWp | 12–15 panels | £7,000 – £9,500 | Larger homes | Better suited for energy-intensive households |
7+ kWp | 16+ panels | £10,000+ | Commercial/landlord | May require bespoke ballasted mounting and DNO approval |
What Solar Panel Grants and Incentives Are Available in the UK?
Installing solar panels is a smart investment for long-term savings, but upfront costs can still be a concern for many homeowners and landlords.
Fortunately, there are several UK-based solar panel grants and financial incentives that can reduce the cost of your installation, particularly if you’re upgrading an energy-inefficient property or supporting low-income tenants.
Below are the most relevant schemes and incentives currently available in the UK:
ECO4 Scheme (Energy Company Obligation)
The ECO4 scheme, managed by Ofgem, helps low-income and fuel-poor households across the UK improve their home's energy efficiency. This includes funding for solar panel installation in certain cases, particularly when part of a whole-home retrofit.
Home Upgrade Grant (HUG) – England only
The Home Upgrade Grant (HUG) is aimed at low-income households off the gas grid. While not exclusively a solar grant, it can help cover the cost of renewable technologies including solar PV as part of a wider retrofit.
Local Authority Delivery Schemes
Some councils and combined authorities offer their own grant or funding schemes for renewable installations under sustainability or retrofit programmes.
- Eligibility: Varies by council; may include income caps, EPC ratings, or other criteria.
- How to find: Check your local council’s website or the Simple Energy Advice tool to explore your local options.
Important Note: Grant availability may depend on your roof’s condition, orientation, or type, so it’s worth consulting an expert to check if your fibreglass roof qualifies under any of the schemes mentioned above.
Smart Export Guarantee (SEG)
The Smart Export Guarantee (SEG) is not a grant but an incentive that allows you to earn money for the electricity your solar panels export back to the National Grid.
0% VAT on Solar Panel Installations
As of April 2022, the UK government introduced 0% VAT on the installation of energy-saving materials, including solar panels, in residential properties. This reduction is in effect until March 2027.
Are There Planning Permission Requirements?
Most solar panel installations in the UK fall under Permitted Development Rights, but there are exceptions:
- If your property is listed or in a conservation area
- If panels will protrude more than 200mm above the roof surface
You should always check with your local planning authority before proceeding.
How Do Fibreglass Roofs Compare To Other Roof Types For Solar?
If you're still weighing your options or have different buildings with varied roof types, here's a quick comparison:
Roof Type | Solar Compatibility | Mounting Difficulty | Durability Under Panels |
|---|---|---|---|
Fibreglass | Moderate | Medium | High |
EPDM Rubber | Moderate | Medium | Moderate |
Slate | High (pitched) | Difficult | Moderate to Low |
Concrete/Flat | High | Easy | High |
Concrete roofs, especially flat ones, tend to offer a very stable and straightforward platform for solar panels, often requiring fewer mounting adjustments.
Similarly, EPDM rubber roofs share many of the same characteristics as fibreglass roofs, particularly in their flat design and installation needs.
However, they can be more susceptible to punctures and may require more cautious handling during solar panel mounting. You can learn more in our detailed article on installing solar panels on rubber roofs.
FAQs
1. Can solar panels cause fibreglass roofs to leak?
When installed incorrectly, yes. However, reputable installers use either ballasted or sealed mounting systems to preserve waterproofing.
2. How long will a fibreglass roof last under solar panels?
A GRP roof typically lasts 25-30 years. With solar panels acting as a protective layer, lifespan can be extended if the installation is done properly.
3. Can I install solar panels on an older fibreglass roof?
It depends on the condition. A roof inspection is strongly advised. If the fibreglass is brittle, cracked, or water-damaged, replacement may be needed before solar installation.
4. Will solar panels make maintenance of my roof more difficult?
Panels can limit access, but a good installer will design the layout to allow access paths. This is especially important for flat roofs.
5. Are there insurance implications with fibreglass roof solar installations?
Yes, you should notify your insurer. Some policies may need to be adjusted to account for the added value or risk.
Final Thoughts
So, can you install solar panels on a fibreglass roof? Absolutely, as long as the roof is structurally sound and the right mounting system is used.
While fibreglass roofs present a few unique challenges, they are a viable and increasingly common surface for solar panel installation in the UK.
With the right planning, qualified installers, and support from tools like the Eco Answers Quote Comparison Tool, homeowners, landlords, and commercial property owners can confidently transition to clean, renewable energy.