Whether you’re working on a utility upgrade, telecom infrastructure, renewable energy installation, or transport system expansion, choosing the right enclosure for your equipment is crucial. A poor choice can lead to equipment failure, costly downtime, and unnecessary maintenance.
That’s why GRP enclosures (Glass Reinforced Plastic) are rapidly becoming the go-to solution across a wide range of industries. They’re durable, lightweight, non-corrosive, and highly customisable — but with so many options available, how do you know which GRP enclosure is right for your project?
In this comprehensive guide, we’ll walk you through everything you need to know before selecting a GRP enclosure — including features, customisation options, application requirements, and expert tips to help you make the right decision.
What Are GRP Enclosures?
GRP enclosures are protective cabinets or housings made from a composite material of plastic resin and glass fibres. Also known as fibreglass enclosures, they are widely used to protect electrical, mechanical, and communication equipment in challenging outdoor and industrial environments.
✅ Key Properties of GRP Enclosures:
- Weatherproof and UV-resistant
- Corrosion-proof
- Electrically non-conductive
- Thermally insulated
- Impact and tamper-resistant
- Long-lasting (20+ years lifespan)
- Lightweight for easy installation
Why Choose GRP Over Other Materials?
When compared to metal, wood, or basic plastic enclosures, GRP offers several advantages:
| Feature | GRP Enclosure | Metal Box | Plastic Box |
| Corrosion Resistance | ✅ Excellent | ❌ Requires coating | ⚠️ Moderate |
| Weight | ✅ Lightweight | ❌ Heavy | ✅ Lightweight |
| Electrical Insulation | ✅ Naturally non-conductive | ❌ Conductive | ✅ Non-conductive |
| Customisability | ✅ High | ⚠️ Limited | ⚠️ Limited |
| UV Resistance | ✅ Excellent | ❌ Requires paint | ⚠️ May degrade |
| Maintenance | ✅ Low to none | ❌ High | ⚠️ Moderate |
Step-by-Step Guide to Choosing the Right GRP Enclosure
1. Define the Application
Understanding your specific use case is the first step. GRP enclosures are used in a variety of industries, such as:
- Utilities: Electrical switchgear, pump controls
- Telecoms: Broadband nodes, antenna bases
- Renewables: Solar inverters, wind battery storage
- Traffic & Rail: Signal controls, ANPR systems
- Construction: Temporary distribution boards
- Water & Environmental: Monitoring and sampling stations
👉 Ask Yourself:
- What type of equipment will it protect?
- Will it be installed outdoors, underground, or in a public area?
- Will it require ventilation, insulation, or heating?
2. Determine Size and Dimensions
Choosing the right size enclosure is essential to ensure easy installation, maintenance access, and future scalability.
🔹 Consider:
- The size and weight of internal components
- Space for wiring, mounting brackets, and ventilation
- Space for future upgrades or expansions
GRP cabinets from manufacturers like Adept GRP come in standard sizes or can be fully custom-built to meet unique project requirements.
3. Check Ingress Protection (IP) Rating
The IP rating determines how well the enclosure protects against dust and water. For outdoor use, a minimum of IP55 is recommended, but IP65 or higher is preferred for harsh environments.
| IP Rating | Protection Level |
| IP54 | Dust protection, splash water |
| IP55 | Dust protection, low-pressure water jets |
| IP65 | Complete dust-tight, low-pressure water jets |
| IP66 | Complete dust-tight, strong water jets |
👉 Choose a higher IP rating for exposed or coastal locations.
4. Evaluate Thermal and Electrical Safety
GRP is naturally non-conductive and provides excellent thermal insulation, reducing risks of short circuits and equipment overheating.
If your enclosure will house electrical or heat-sensitive equipment, ask about:
- Internal cooling systems or vents
- Double-skin insulation panels
- Fire-retardant resin options (BS 476 Part 7 Class 2 or Class 0 rated)
5. Consider Environmental Resistance Needs
Your enclosure must survive the real-world conditions of its environment. Depending on your location, you may need features like:
- UV-stabilised surface gel coat (for sun exposure)
- Anti-graffiti coating (urban or public spaces)
- Salt-resistant finish (coastal regions)
- Chemical-resistant material (industrial or treatment plants)
GRP enclosures are ideal for marine, desert, and industrial zones where traditional materials would quickly degrade.
6. Select Security & Locking Features
Security is critical when placing enclosures in public or remote locations. Common options include:
- Stainless steel hasp and staple locks
- Hidden hinges and recessed handles
- Tamper-proof fasteners
- Alarm integration
Some projects may also require double-door access, internal compartments, or restricted tool access for added safety.
7. Think About Internal Layout & Mounting
GRP enclosures can be supplied fully assembled with internal features such as:
- Shelves and trays
- DIN rails or backboards
- Cable glands and knockouts
- Mounting brackets and fixing kits
This ensures your installation team can work faster and more efficiently on-site.
8. Customisation & Branding Options
If your enclosure will be seen by the public or needs to match company assets, GRP allows full custom colours, logos, and signage directly moulded or printed onto the cabinet.
Customisation options include:
- RAL colour matching
- Company logos or labels
- Reflective safety stickers
- Anti-vandal texture finishes
9. Regulatory & Safety Compliance
Make sure your GRP enclosure complies with relevant UK and EU standards, such as:
- BS EN 62208: Empty enclosures for low-voltage switchgear
- BS 476: Fire performance rating
- ISO 9001: Manufacturing quality assurance
Suppliers like Adept GRP manufacture to strict quality standards, ensuring full compliance for industrial and public sector projects.
Common Mistakes to Avoid
- ❌ Underestimating size needs — always allow room for access and upgrades
- ❌ Ignoring IP ratings for outdoor installs
- ❌ Choosing standard models for extreme conditions instead of custom builds
- ❌ Overlooking branding and access control in public-facing projects
- ❌ Using metal boxes in corrosive or exposed locations
Why Choose Adept GRP?
At Adept GRP, we provide bespoke GRP enclosures tailored to your project’s specific requirements. Our team will guide you through:
- Material selection
- Ventilation and internal layout
- Locking and mounting systems
- Branding, colour matching, and fast lead times
With decades of experience serving sectors like utilities, telecoms, transport, and renewables, we deliver high-quality, UK-manufactured GRP enclosures with performance you can trust.
Conclusion
Choosing the right GRP enclosure is not just about protecting your equipment — it’s about ensuring safety, efficiency, and long-term reliability for your entire operation.
By understanding your application, environment, and customisation needs, you can select a cabinet that performs consistently in even the harshest conditions.
