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1 Gang 35mm Galvanised Steel Back Box

£149
The RRP is the manufacturer's recommended retail price of the item.
Limited Stock
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Minimum order for this item is 10.

Description

This Knightsbridge 1-gang 35mm galvanised steel back box provides the recessed housing for a single-gang electrical accessory, measuring 73mm square with a 35mm recess depth. The box is pressed from 1mm-thickness galvanised steel, giving corrosion resistance in damp or condensation-prone environments where standard metal boxes may rust over time.

Designed for installation into masonry, plasterboard and timber stud walls, the box has one fixed mounting lug at the top and one adjustable lug at the bottom, allowing the faceplate fixing points to be aligned horizontally even when the box itself sits slightly off-square in the wall cavity. An integrated earth terminal inside the box provides a bonding point for the earth conductor. 20mm knockouts on the sides and rear accept standard conduit entries and cable glands.

The 35mm depth accommodates deeper devices such as dimmer modules, USB charging sockets, or installations where multiple cables terminate in the same box and additional space is needed behind the faceplate. The galvanised finish on the steel provides a zinc coating that protects the base metal from oxidation in kitchens, bathrooms, utility rooms and external covered installations where moisture ingress is a concern.

Specification
Height 73 mm
Width 73 mm
Recessed Depth 35 mm
Construction Steel
Earth Terminal Yes
Warranty 25
Downloads

Product Specification Sheet

Frequently Asked

What's the difference between 25mm and 35mm back boxes?

A 25mm box is the standard depth for most single-gang switches and sockets. A 35mm box provides an extra 10mm of recess depth, which is needed for dimmer switches, USB sockets, smart switches, or installations where multiple cables terminate in the same box and additional clearance is required behind the faceplate.

Can this be used in bathrooms?

Yes. The galvanised steel finish provides corrosion resistance in damp environments. The box should still be installed in compliance with BS 7671 wiring regulations, which specify minimum distances from water sources and zoning requirements for bathroom electrical installations.

What size wall opening is needed?

The box measures 73mm square externally. A wall opening of approximately 75-76mm square is typically cut to allow the box to be recessed into the cavity with minimal gap around the edges, which is then filled during plastering or making good.

Are the lugs adjustable for levelling?

The top lug is fixed. The bottom lug is adjustable, allowing the faceplate fixing points to be aligned horizontally even when the box sits slightly off-square in the wall. This prevents faceplates from appearing tilted after installation.

Shipping & Returns

Delivery UK delivery is £14.99, and delivery is free on all orders of £99 or more, in the UK and internationally.

Returns If you change your mind, you have 14 days from delivery to tell us, and a further 14 days to send the goods back. Return postage for a change-of-mind return is paid by you. Change-of-mind returns are subject to an inspection and handling deduction. See our full returns policy.

To arrange a return, call us on 020 8149 5199 or use our contact page.

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    Description

    This Knightsbridge 1-gang 35mm galvanised steel back box provides the recessed housing for a single-gang electrical accessory, measuring 73mm square with a 35mm recess depth. The box is pressed from 1mm-thickness galvanised steel, giving corrosion resistance in damp or condensation-prone environments where standard metal boxes may rust over time.

    Designed for installation into masonry, plasterboard and timber stud walls, the box has one fixed mounting lug at the top and one adjustable lug at the bottom, allowing the faceplate fixing points to be aligned horizontally even when the box itself sits slightly off-square in the wall cavity. An integrated earth terminal inside the box provides a bonding point for the earth conductor. 20mm knockouts on the sides and rear accept standard conduit entries and cable glands.

    The 35mm depth accommodates deeper devices such as dimmer modules, USB charging sockets, or installations where multiple cables terminate in the same box and additional space is needed behind the faceplate. The galvanised finish on the steel provides a zinc coating that protects the base metal from oxidation in kitchens, bathrooms, utility rooms and external covered installations where moisture ingress is a concern.

    Specification
    Height 73 mm
    Width 73 mm
    Recessed Depth 35 mm
    Construction Steel
    Earth Terminal Yes
    Warranty 25
    Downloads

    Product Specification Sheet

    Frequently Asked

    What's the difference between 25mm and 35mm back boxes?

    A 25mm box is the standard depth for most single-gang switches and sockets. A 35mm box provides an extra 10mm of recess depth, which is needed for dimmer switches, USB sockets, smart switches, or installations where multiple cables terminate in the same box and additional clearance is required behind the faceplate.

    Can this be used in bathrooms?

    Yes. The galvanised steel finish provides corrosion resistance in damp environments. The box should still be installed in compliance with BS 7671 wiring regulations, which specify minimum distances from water sources and zoning requirements for bathroom electrical installations.

    What size wall opening is needed?

    The box measures 73mm square externally. A wall opening of approximately 75-76mm square is typically cut to allow the box to be recessed into the cavity with minimal gap around the edges, which is then filled during plastering or making good.

    Are the lugs adjustable for levelling?

    The top lug is fixed. The bottom lug is adjustable, allowing the faceplate fixing points to be aligned horizontally even when the box sits slightly off-square in the wall. This prevents faceplates from appearing tilted after installation.

    Shipping & Returns

    Delivery UK delivery is £14.99, and delivery is free on all orders of £99 or more, in the UK and internationally.

    Returns If you change your mind, you have 14 days from delivery to tell us, and a further 14 days to send the goods back. Return postage for a change-of-mind return is paid by you. Change-of-mind returns are subject to an inspection and handling deduction. See our full returns policy.

    To arrange a return, call us on 020 8149 5199 or use our contact page.