GRP vs Stainless Steel Enclosures: Which to Choose

GRP or stainless steel: which enclosure suits your install?

Choosing an enclosure usually comes down to where it sits, what it holds and how little attention it needs over its life. Stainless steel and painted steel are common choices. Glass reinforced plastic (GRP) is the other main option. This page sets out the trade-offs so you can choose the right material for the job.

The short answer

Choose GRP for outdoor sites, damp or corrosive areas, and any installation where a non-conductive enclosure is wanted.
Choose stainless steel where a specification calls for metal, or where a metal enclosure is required by the design.

Our enclosures are IP55-rated and manufactured in Wales.

Weight

GRP is generally lighter than a steel enclosure of the same size. Weight still matters for GRP, especially on larger units. Our walk-in enclosures are a good example. The FW2 weighs 140 kg and the FW4A weighs 240 kg. Plan for lifting, access and the route into the plant room before you order, whatever the material.

Corrosion

GRP does not rust, so it needs no protective coating and there is no paint to chip or touch up. Stainless steel also resists corrosion well. How well it performs depends on the grade and the environment, so check the grade against your site before you specify it.

Electrical properties

GRP does not conduct electricity. There is no metal body to bond or to become live if a fault occurs inside the enclosure. Earthing arrangements still follow your installation design, but the enclosure itself is not a conductive path.

Maintenance

GRP needs little ongoing work. Check seals, hinges and locks at routine inspections, and keep the surface clean. Painted steel needs repainting once the coating is damaged. Stainless steel needs cleaning to keep its finish looking good.

Cost

Compare the full installed cost, not the unit price alone. Include delivery, lifting, fixing and the maintenance you expect over the life of the enclosure. Our list prices are ex VAT. GRP single door cabinets start from £605 + VAT (FS1), and GRP walk-in enclosures start from £2,435 + VAT (FW1). Ask for a quote if you want a like-for-like comparison against a steel specification.

When stainless steel may suit better

The specification, the client or the standard you work to calls for a steel enclosure.
The design needs a metal enclosure for a specific electrical or screening reason.
The enclosure sits inside a dry, controlled space and a metal finish is preferred.

Indoor plant rooms or outdoor sites

Indoors, the main reasons to choose GRP are the non-conductive body and low maintenance. Outdoors, the enclosure faces weather and exposure, so check the IP rating and how the unit is sited. IP55 means the enclosure is protected against dust and low-pressure water jets.

Frequently asked questions

Is GRP a good choice for outdoor electrical enclosures?

Yes, for many outdoor installs. GRP does not rust, it is non-conductive and our enclosures are IP55-rated. Check the siting and the cable entry arrangements against your design.

Does a GRP enclosure need painting?

No. Our cabinets and enclosures are available in Grey or Green.

Is GRP cheaper than stainless steel?

It depends on size, specification and what you include in the comparison. We do not publish steel prices. Request a quote with your dimensions and we will price the GRP option for you to compare.