An electrician wired a rear extension at the heights he'd used for fifteen years, and building control refused sign-off on the spot: the extension fell under Part M, and both socket and switch heights sat outside the accessible zone.

What Is the Accessible Zone Under Part M?

Approved Document M states that switches, socket outlets and similar controls should be positioned so their centre line falls between 450mm and 1200mm above finished floor level. The logic is straightforward: someone using a wheelchair, or anyone with restricted reach or mobility, needs to operate a switch or plug something in without bending to the floor or stretching overhead.

Where Does Part M Apply, and Where Doesn't It?

This is the point that causes the most confusion on site. Part M is a Building Regulations approved document, which means it applies where Building Regulations sign-off is required.

That last point matters for landlords and property managers doing routine EICR remedial work: swapping a faceplate or replacing a faulty socket in its existing position generally doesn't require repositioning to meet Part M, because the work isn't itself notifiable under the regs that trigger the accessible-design requirement. Many electricians still choose to bring accessories into the 450mm to 1200mm band wherever practical, because it costs nothing extra during a rewire and future-proofs the installation.

Why Does This Matter Beyond Strict Compliance?

Outside strict Part M triggers, the accessible band is worth specifying as standard practice on any full rewire, HMO refurbishment, care home fit-out, or hotel guest room programme, properties where the occupant on any given day is unknown and may have limited mobility or be a wheelchair user. Getting it right at first fix avoids exactly the re-chasing cost in the story above, and it removes a recurring point of friction on care and assisted-living contracts where accessible design is scrutinised regardless of whether Part M is formally triggered.

How Do You Get It Right on Site?

1. Confirm whether the job is Building Regulations-controlled before first fix: new build, extension and most conversions are; a straight like-for-like swap usually isn't.
2. Mark out at 450mm and 1200mm before chasing, not after: moving a back box after plastering is the expensive mistake, not the height check itself.
3. Measure to the accessory centre, using the back box centre line as your reference, not the top or bottom edge of the finished plate.
4. Apply it consistently across a project even on rooms Part M doesn't strictly cover, so a hallway meeting the standard doesn't sit against a kitchen that doesn't.

Frequently Asked Questions