Measuring Blinds for Non-Standard Windows: Bay Windows, Skylights, Bifold Doors, and More

Why Non-Standard Windows Require Extra Care

A standard rectangular window in a flat wall is relatively forgiving. Non-standard windows — bay windows, sloped ceilings, skylights, and bifold door openings — present specific challenges that a general measuring guide will not fully address. Rushing the measuring process on these windows is where the most expensive mistakes happen.

The overriding principle across all non-standard windows is this: when in doubt, photograph the window, write down every dimension you can measure, and email estimates@newblinds.co.uk before ordering. Advice, product recommendations, and quotations are available at no obligation.

How Do You Measure Blinds for Bay Windows?

Should each window in a bay be measured individually?

Yes, without exception. Even windows that appear visually identical within the same bay are rarely the same size. Measure each window individually and label each measurement clearly — for example, "Bay Left," "Bay Centre," "Bay Right."

What else should you consider for bay windows?

The angled junction between adjacent windows in a bay can restrict how far a blind's headrail protrudes. Check that the chosen blind type's bracket projection from the wall does not cause adjacent blinds to foul each other at the angled corners. For complex bay configurations, email the estimates team with photographs and all measurements.

How Do You Measure Blinds for Skylights and Roof Windows?

What information is needed for branded skylights?

For branded roof windows — Velux, Fakro, Dakstra, and Rooflite — you do not need to manually measure the glass. Instead, locate the window code or model number on the frame or in the original installation documentation. This code is all that is required to identify the correct blind.

What if my skylight is not a branded window?

For custom or non-branded skylights, manual recess or blind size measurements are required for our Electric Pleated Skylight Blinds. A written measuring guide is available at newblinds.co.uk and a measuring video at youtu.be/VAbMmaqPvpw.

How do you safely access a skylight to measure it?

Use a suitable ladder or scaffolding tower rated for the height involved. Do not attempt to measure a roof window by stretching across from a step stool or working from an unstable platform. 

What blind types are compatible with skylights?

Compatible blind types include those specifically designed for Velux, Fakro, Dakstra, and Rooflite windows, available in manual (with a control rod option) and solar-powered motorised versions.

How Do You Measure Blinds for Bifold Doors?

What information do you need before measuring bifold door blinds?

Before taking any measurements, establish the following:

• How many panels does the bifold door have?
• Do the panels stack inward or outward when the door is open?
• How many blinds do you want — one per panel, or a single blind (or pair of blinds) covering the full opening?
• Where do you want to fit the blind — within the recess, on the wall above, or on the door frame itself?

Why does the stack direction matter?

Whether the panels fold inward or outward determines whether the blind needs to be installed in a position that does not obstruct door operation. A blind fitted inside the recess on a bifold door that folds inward must be installed high enough to clear the folding panels.

Can a single blind cover the full bifold door opening?

This depends on the blind type and its maximum width. Many bifold door openings exceed the maximum width of a single blind. In these cases, two or more blinds are required side by side. Roller blinds will have a larger visible gap between adjacent blinds than pleated blinds fitted in the same position.

How do you label measurements for a multi-panel bifold door order?

Provide the full opening measurement, confirm the number of panels, and specify how many blinds you would like and how you want the opening divided. If you are unsure how to split the order, email customer.services@newblinds.co.uk for guidance.

What About Angled or Shaped Windows?

Shaped windows — with triangular shaped frames — are not available to order through the standard website. Contact estimates@newblinds.co.uk with your measurements, a photograph or drawing, your preferred blind type, control method, and fabric requirements. Advice can be given and a quotation provided.

How Do You Handle Windows with Radiators, Handles, or Obstructions?

Radiators below the window: A blind sitting in front of the heat source when closed can reduce heating efficiency and may cause the fabric to discolour over time. Consider a shorter drop or a face-fixed blind positioned higher on the wall, so the drop sits above the radiator when the blind is closed.

Projecting handles and locks: Measure the depth of any projecting handle within the recess. If the handle projects further than the recess depth allows a blind to sit, a face-fixed blind above the window is the practical solution. For roller blinds within the recess, reverse roll can help the fabric clear handles as it descends.

Trickle vents: If the recess has a trickle vent along the top or sides, the blind bracket position may need to be adjusted to clear it. In some cases, fixing the blind above the recess is a more practical approach.