Back

Composite Door Measuring Guide


28 September 2026

This is only a guide to help an experienced tradesperson or competent DIYer carry out a survey. We do not accept any liability for inaccurate surveys.

The Do’s and Don’ts

Follow these simple do's and don'ts to ensure that you get the most out of your new door:

Do’s

  • Do make sure you have a metric tape measure

  • Do make sure you write each measurement down in-between taking new measurements

  • Do ensure you allow sufficient clearance in the height, width and bottom clearance for the door to open fully

  • Do make sure you check which side you want the handle (You must do this as you look at the door from the outside)

  • Do make sure that the door is smaller than the opening


Don'ts

  • Don’t use an old tape measure where it is difficult to read the measurements

  • Don’t use a linen or paper tape measure like a dressmakers tape

How to Measure for a New Composite Door

You are measuring the overall width and height of the door including the door, the frame and cill.

composite-door-measuring-guide-diagram

Addon Example

composite-door-addon-diagram

Box Sash Plan View

You may have a box sash scenario when the reverse of the plan view is shown in fig.5. You will need to measure brick to brick externally then add 5-10mm each side (to the smallest size), so the outer frame sits nicely behind the existing brickwork. With a box sash installation the frame can be fixed with a frame addon to make up the gap. Addons available in 15, 25 & 50mm (It will be necessary to remove existing architrave to survey accurately.)

composite-door-box-sash-plan-view

Cill Options

When entering sizes for manufacture they included the cill which is 30mm high if required.

composite-door-cill-options