How to measure a door gap for a draught excluder

Most disappointments with draught excluders come down to the wrong size. A seal that is too thin never touches the floor, and a seal that is too thick jams the door. Five minutes with a tape measure avoids both.

Measurement 1: the width of the door

Measure the door leaf along its bottom edge, from the hinge side to the latch side, not the frame. Standard UK door widths are:

• Internal doors: 686mm, 762mm or 813mm
• Front and back doors: 838mm or 914mm
• Double and patio doors: much wider, often more than a metre

A 90cm excluder suits the majority. An 81cm one suits narrow internal doors, and a 107cm one is for wider openings.

Measurement 2: the gap under the door

Close the door and measure from the underside of the door to the floor. Do it at the hinge end, the middle and the latch end, because floors are rarely level and doors often drop slightly. Use the largest number when comparing products. Product pages on this site list a maximum gap fill so you can compare directly.

Measurement 3: door thickness (for twin-sided covers)

A cover that slides over the door must fit around it. Measure the thickness of the door edge. Most internal doors are 35mm and most external ones 44mm, but old doors vary.

Measuring a narrow gap around a frame

For the gap between a door and its frame, or a window and its frame, slide a thin card into the gap. A credit card is about 0.8mm thick, so stacking three means a gap of around 2.5mm. Compare with the gap range on a tape or a P-profile seal, and choose one a little thicker so it is lightly squeezed when the door is closed.

Allow for the floor

A hard floor gives a clean measurement. A carpet adds a soft surface that squashes. If you are fitting a sweep, set it so it only just touches the carpet, otherwise it will drag.

Quick reference

Once you have these numbers, browse the under door excluders, the door seals or the draught tape with confidence.