1 Gang 16mm Deep Galvanised Standard Extension Box

Add essential depth to your electrical installations with this 1 gang 16mm deep galvanised standard extension box—ideal for adjusting flushness or accommodating extra wiring behind switches and sockets. Part of our core range of electrical accessories, this robust metal box is precision-engineered for reliable performance in both domestic and light commercial settings. Made from durable galvanised steel with a matte-silver finish, it resists corrosion and ensures long-term stability. The 16mm depth provides just enough space to extend existing back boxes without compromising wall integrity. Available as a single-gang unit with standard UK dimensions, it’s compatible with all conventional faceplates and mounting hardware. Perfect for retrofitting, repairs, or fine-tuning alignment during new builds. Explore more options in our dedicated back boxes collection.

Key Features

• 16mm deep galvanised steel construction for durability and rust resistance
• Standard single gang size (86mm x 86mm) fits all UK switch and socket plates
• Includes pre-formed knockouts for easy cable entry
• Ideal for extending shallow existing back boxes
• Matte silver finish matches industrial and modern electrical fittings
• Supports secure screw mounting via integrated lugs
• Essential electrical accessory for tidy, compliant installations

FAQs

Can this extension box be used with existing plastic back boxes?

Yes, this galvanised steel extension box is designed to fit over standard 1 gang plastic or metal back boxes to add 16mm of depth. It aligns with common UK faceplate dimensions and uses the same fixing points.

Is this suitable for use in walls with plasterboard or drylining?

Absolutely—it can be fixed directly to the front of an existing back box in plasterboard, timber stud, or masonry walls. Ensure the underlying box is secure, as this extension relies on the original mounting for structural support.