Measure a Door for a Smart Lock: Backset & Centres

A smart lock can have the right appearance and still fail to fit the door. Door thickness, backset, lock centres, fixing centres and panel dimensions describe different measurements. Record each against the selected installation drawing rather than sending a single approximate size.

The illustration is a measurement guide, not a drilling template. Dimensions, reference surfaces and allowed preparation vary by lock type. Keep an existing lock in place unless removal is authorized and can be performed safely; ask the installer to inspect concealed parts.

Measure the door leaf between its two faces at the proposed lock position. Do not include a projecting handle or escutcheon. Tell the supplier about additional cladding, a rebate, a glass profile or other features that affect the mounting surfaces. Photograph the measurement so the reference points are clear.

For a typical bored lock, backset is the horizontal distance from the door edge to the centre of the bore. A mortise drawing identifies its own faceplate reference and spindle or cylinder centre line. Follow that drawing, especially on a rebated or profiled door. A panel's width is not its backset.

On a mortise assembly, record the centre-to-centre spacing between the handle spindle and cylinder or key opening when the drawing calls for it. Fixing centres describe the positions of mounting holes and are a separate measurement. Indicate which two points you measured; a number labelled only centres is ambiguous.

A familiar code such as 6068 is not a substitute for a drawing. Confirm the selected case, faceplate, hole positions and any handing or multipoint requirements. Avoid decoding a catalogue label into installation dimensions without the supplier's confirmation.

Record the existing faceplate length and width, lock-case pocket if accessible, panel clearance, handle sweep and frame strike position. Check whether the new panel covers existing holes without interfering with trim. An installer should assess any cutting or drilling: do not enlarge a pocket simply because a panel can cover the alteration.

For example, 196 lists 30–50 mm doors, 150 × 64 mm front/rear panels and 60 / 70 mm latch backset options. CB2 lists 50–100 mm doors and different front/rear panel dimensions: 385 × 70 × 49 mm and 435 × 70 × 59 mm. These are catalogue examples for different platforms, not universal smart-lock dimensions.

Use millimetres consistently and label all photos. Add the door material, opening direction, existing lock and strike photographs, chosen model and app version. Ask for the installation template and included lock body to be confirmed in writing, then evaluate the approved sample on a representative door.