How to Measure Window Handles for Double Glazed Windows

Measuring window handles for double glazed windows requires precision to ensure a correct replacement and smooth operation. This guide provides clear, actionable steps for homeowners and tradespeople to measure different handle types commonly found on double glazed units, explains which dimensions matter, and highlights common pitfalls to avoid during measurement.

Identify the handle type

Different handle types demand different measurements. Common varieties on double glazed windows include espagnolette (espag) handles, cockspur handles, and sash handles. Espag handles connect to an internal espagnolette locking mechanism via a spindle and need measurements such as spindle size and screw centres. Cockspur handles fit over the frame with visible fixings and require centre-to-centre screw measurements and projection checks. Identifying the style first simplifies measurement and helps select a compatible replacement such as the TSS Cockspur Window Handles, TSS Cockspur Window Handle, or TSS Offset UPVC Window Handles.

Tools required

Preparedness reduces errors. Essential tools:

• A steel rule or tape measure with millimetre graduations.
• Digital calipers for precise thickness and diameter measurements.
• A vernier or small spirit level to confirm handle perpendicularity if required.
• Pen and paper or smartphone camera to record and photograph existing handle and fixation points.

Measure screw centres (backplate handles)

Many replacement handles are specified by screw centres — the distance between the two fixing screw holes measured centre-to-centre. Steps: 1. Fully close the window so the handle is in its normal closed position. 2. Measure horizontally between the centres of the two fixing screw holes on the handle backplate. Record in millimetres. 3. If the screw heads are painted over or countersunk, remove one screw slightly to reveal the true centre before measuring. 4. For handles with only one visible screw, measure the distance from the visible fixing to the handle spindle centre and note the projection.

Screw-centre accuracy is critical because an incorrect centre can prevent proper mounting or leave the handle unstable.

Measure spindle length and size (espag handles)

Espag handles rely on a square spindle that passes through the frame into the locking mechanism. Two measurements are required: spindle size (thickness) and spindle length.

• Spindle size: Measure the width of the square spindle across flats in millimetres. Common sizes are 7mm and 8mm on domestic double glazing.
• Spindle length: Measure the full length of the spindle from the face of the handle backplate to the end of the spindle protruding into the frame. If the spindle is removable, remove the handle and measure the exposed spindle length on both sides if attempting a reversible handle replacement.

If the existing spindle has been trimmed, measure carefully and consider fitting a new spindle of correct length or ordering a handle with a longer spindle that can be cut to size.

Measure backset and handle projection

Backset refers to the distance from the outside edge of the handle backplate to the centre of the spindle or the fixing. For window furniture with face-fixings, the backset affects handle alignment with the locking keeps. Projection is the distance the handle extends from the face of the window when in the rest position.

• Measure the backset horizontally from the frame edge to the spindle centre.
• Measure projection from the frame face to the furthest point of the handle while it is in the closed position.

Incorrect projection can cause the handle to clash with nearby trimmings, curtains or blinds.

Height and orientation measurements

For vertically sliding sashes or tilt-and-turn windows, the vertical position of the handle on the sash matters. Measure from the window sill or frame bottom to the centre of the spindle for a record of handle height. Note the handedness or orientation: whether the handle operates on the left or right side and whether the rotation is clockwise or anti-clockwise when opening. Handing influences the choice of handle or whether a reversible option is required.

Faceplate and backplate dimensions

Record the full height and width of the backplate or faceplate, especially when replacing handles mounted on decorative plates. Some modern multi-point locking handles require matching plate lengths or a particular bolt/keep position. Measure:

• Plate height (top to bottom)
• Plate width (side to side)
• Distance from top of plate to centre of spindle and to screw centres

This helps to ensure the new handle covers any existing drill holes and aligns with the locking mechanism.

Check for additional features

Certain handles include features that affect compatibility:

• Key locking: note whether a key cylinder is integral and whether a replacement requires a keyed option.
• Non-handed vs handed: some handles are reversible, others fixed-handed.
• Security standards: some handles are designed to be PAS24 compliant or come with anti-snap and anti-rotation features.

Record these requirements to match the security level of the original hardware.

Record and photograph

Create a measurement sheet listing all dimensions in millimetres and take clear photos from multiple angles: front, side and inside view of the spindle area. Photos help suppliers confirm compatibility and speed up sourcing replacement parts.

Common pitfalls and solutions

• Relying on nominal sizes: check actual measurements, not assumed common sizes.
• Measuring the wrong centre point: confirm the centre of screw holes, not the outer edge.
• Ignoring handedness: ensure rotation direction and orientation are recorded.
• Overlooking obstructions: curtains, bars or trimmings can interfere with handle operation; check projection and clearance.

Tradespeople should double-check measurements on site and take spares if possible. Homeowners ordering online should opt for handles that include adjustable or reversible components where available.

Final selection and fitting tips

Select a replacement handle that matches the measured screw centres, spindle size and length, backset and plate dimensions. Consider choosing a handle with improved security features if the existing handle is older. During fitting, ensure fixings are tightened evenly, the spindle is fully engaged with the locking mechanism, and moving parts operate smoothly with no binding.

For technical specifications and product selection, popular options include the TSS Cockspur Window Handles, the TSS Cockspur Window Handle and the TSS Offset UPVC Window Handles.

Further detailed guidance on styles, security ratings and compatibility is available in the comprehensive Window Handles Guide.