Standard & Made-to-Measure Bifold Door Sizes (UK Guide)

Bifold door sizes follow your opening, not a fixed product list. Aluminium systems commonly span from around 1.8 metres up to 6 metres or more, in two to six panels, at heights between roughly 2000mm and 2400mm. These are useful guide figures, not promises. A survey always confirms your final frame size before anything is manufactured.

Sizes follow the opening. That is the short answer to almost every question about door sizes, and a professional survey always sets the final figure, not a size chart.

This guide covers typical widths, heights and panel counts for UK homes, from a narrow Victorian terrace opening to a six metre new build extension. Aluminium is usually made to measure, so treat every figure below as a starting point for your own opening, not a fixed rule.

Bifold Door Sizes at a Glance

Most UK openings fall between 1.8 metres and 6 metres wide, using two to six panels. Height typically sits between 2000mm and 2400mm, though this varies by system. The table below gives a quick reference before you measure your own opening.

Overall width	Panels	Typical use
1.8m to 2.1m	2	Small openings
2.4m to 3m	3	Kitchen extensions
3.2m to 4m	4	Standard rear extensions
4m to 6m	5 to 6	Full width openings
Height		Typically 2000mm to 2400mm

These figures are a guide, not a product list. If you already know you want our aluminium bifold door range, send us your rough opening size, and we will talk through what fits before you book a survey.

What Are the Standard Sizes of Bifold Doors in the UK?

Standard sizes usually follow fixed retail steps, such as 1.8m, 2.4m, 3m and 4.2m. These suit openings already built to a common width. Standard bi fold door sizes rarely match an older property exactly, which is why most aluminium orders end up made to measure.

Metres	Millimetres	Feet (approx)
1.8m	1800mm	5ft 11in
2.4m	2400mm	7 ft 10 in
3.0m	3000mm	9 ft 10 in
3.6m	3600mm	11 ft 10 in
4.2m	4200mm	13 ft 9 in

Standard height usually sits close to 2090mm to 2100mm externally, though this varies by system and should be confirmed against your own window heads if you want a matching line across the elevation. Standard is only a starting point. Older homes rarely have an opening that matches a retail step exactly, which is where made-to-measure sizing earns its keep.

Size for Aluminium Bifold Door: Panel Widths, Heights and Limits

Aluminium door sizes depend on the system, but panel widths commonly range from about 600mm to 1200mm. Minimum and maximum figures vary by manufacturer, so always confirm your supplier’s exact limits before assuming a size is possible.

Triple glazing adds real weight to each panel, which can reduce the maximum width a system allows. A thermal break inside the frame cuts heat loss without adding much bulk, so a slim sightline and strong thermal performance are not mutually exclusive.

 For narrower openings, our slimline aluminium bifold door guides cover how a slim frame affects panel width and glass area together. I have noticed that buyers often ask for the biggest panel a system allows, assuming bigger always means better value. It does not always work that way. A slightly narrower panel can look proportionally better against a period property’s existing window heads, even if the wider option is technically achievable.

Height follows a similar logic. Taller panels carry more glass weight, so the lintel above the opening needs to be correctly sized for the span, not just tall enough to clear the frame. Aluminium door sizes at the tall end of the range are usually achievable, but only once a survey confirms the lintel and structural opening can actually support it.

How Sizes of doors Decide the Number of Panels

Door sizes and panel count are directly linked. A wider opening needs more panels, or wider individual panels, and the choice between the two changes both the stack and the final cost.

Odd panel counts usually include a traffic door, the single panel you open daily without folding the whole set back. Even panel counts often split from the centre instead. Is more panels always better for a wide opening? Not necessarily. More panels add sightlines across the view, while fewer, wider panels keep the glass area as uninterrupted as possible.

Configuration	Example	Best use
3+0	Three panels, one way	Simple, all panels stack to one side
2+1	Two panels plus a traffic door	Daily access at one end
3+1	Three panels plus a traffic door	Wider openings needing frequent access
2+2	Two panels each side	Opens from the centre

Work through this choice at survey stage, since the right configuration for your opening depends on daily use as much as the raw width.

Structural Opening, Frame Size and Clear Opening: What Is the Difference?

The structural opening is the raw gap in the wall. Frame size is the size you order, slightly smaller to allow for fitting. Clear opening is the actual walk-through width once the frame and folded panels are accounted for, and it is always narrower than the headline size.

Measurement	Example figure	Note
Structural opening	3000mm	Raw brick-to-brick gap
Frame size	2990mm	Structural opening minus fitting tolerance
Clear opening	Around 2700mm	Varies by configuration and traffic door width

This gap between headline width and clear opening catches people out more than almost anything else. A 3 metre bifold does not give you a 3 metre walk-through, since the frame and stacked panels both take up real space. Always ask your supplier for the clear opening figure, not just the overall size, if a specific walk-through width matters to your project.

How Much Space Do Folded Panels Need?

Folded panels need clear wall space beside the opening, roughly equal to the stack width shown on your supplier’s drawing. Check this space both inside and outside before you commit to a configuration.

• Downpipes near the opening
• A wall return that is too short for the stack
• A kitchen island positioned too close
• Radiators under or beside the opening
• Blinds or curtains that would clash when folded back
• Patio furniture left in the stacking zone

An outward opening saves internal floor space, which suits a tight kitchen. An inward opening saves patio space instead, which matters more on a narrow terrace garden. Narrow side access on a terraced house can limit which stacking side is realistic too, since delivery and fitting both need room to manoeuvre a loaded panel into place. 

Here is a decision checkpoint worth pausing on. If your property is a narrow Victorian terrace with a small rear yard, check the stacking space on both sides before you choose a configuration, not just the headline width.

Bifolding Door Sizes for Common UK Openings

Door sizes for common UK openings usually fall into a few repeating patterns: a patio door replacement, a 3 to 4 metre rear extension, or a wide 5 to 6 metre full-width opening.

Replacing a patio or French door with a bifold is often straightforward if the new doors match the existing opening. Widening that opening for a wider bifold usually needs a structural engineer and building control sign-off, so confirm this early rather than assuming it is a simple swap. 

A 2-panel bifold is a reasonable alternative to French doors on a narrower opening, though it carries a wider stack to one side once open. A homeowner in Oxfordshire replacing a rear extension opening with a 4-panel bifold might expect a few weeks for survey and manufacture, plus a single day for fitting, though this varies by supplier and season.

Extension width	Suggested panels	Configuration
3m	3	3+0 or 2+1
4m	4	3+1 or 2+2
6m	5 to 6	Split or traffic door at one end

For very wide openings, a sliding door keeps larger fixed panes of glass, while a bifold gives a fully open wall instead. Both suit different projects. For more on matching material and configuration to your specific property, see our best bifold doors for any property guide.

Thresholds, Floor Levels and the Lintel Above

Your finished floor level and threshold choice both affect the true height of your opening. The lintel above carries the structural load, never the door frame itself, regardless of panel size.

Agree on your finished floor level with your builder before ordering, especially if patio slabs or internal flooring are not down yet. A low threshold needs a properly designed drainage channel to stay watertight, since raised paving outside the door increases the risk of water finding its way in. A homeowner in a 1930s semi widening an old patio door opening should expect the lintel question to come up at survey, not as a surprise once building work has started.

Fitting before or after the screed is a common point of confusion on extension projects. Confirm this sequence with your builder and installer together, in writing, before a fitting date is booked. Reworking a threshold after the floor is laid is far more disruptive than getting it right the first time.

How Does Size Affect Bifold Door Cost?

sizes of Bifold door affect cost directly. A wider opening, more panels, and heavier glazing all add to the price, though the relationship isn’t a straight line when you compare different configurations for the same width.

Width and panel count both matter, but so do glazing spec, colour and threshold choice. Installation time also tends to rise with size, which is worth factoring in alongside the headline figure. Our how long installation takes guide covers typical timings by panel count if scheduling matters to your project.

For a fuller breakdown of cost drivers, see a detailed bifold door price breakdown. The same logic applies whether you are fitting a home extension or aluminium commercial doors into a larger commercial opening, since both scale with width and panel count in a similar way.

Standard Bi Fold Door Sizes or Made to Measure: Which Do You Need?

Standard bi fold door sizes suit a new build opening already built to a common width. Made to measure suits almost everything else, especially older properties where the opening was never built to a standard figure in the first place.

Factor	Standard size	Made to measure
Fit	Close only	Matches your exact opening
Lead time	Often quicker	Usually longer
Cost	Can be lower	Reflects your exact spec
Best for	New build, standard openings	Older homes, awkward openings
Who measures	You confirm against a fixed list	A professional survey

Standard bifold sizes are a useful starting point for budgeting, but they rarely remove the need for a survey. Our made-to-measure guide covers the full sizing process in more depth, including how tolerances and out-of-square openings are handled before manufacture.

Which Regulations Apply to the Size You Choose?

Widening a structural opening usually needs building control sign-off, regardless of the door size you eventually choose. A straightforward like-for-like replacement rarely needs planning permission, though an extension project often does.

Building Regulations cover several areas relevant to sizing: Part L for energy performance, Part K for safety glazing in critical zones, and Part Q for security in new dwellings. A FENSA or CERTASS registered installer can usually self-certify compliance on a replacement project without a separate building control application.

Planning permission depends on your specific extension and property, including whether you are in a conservation area. Always confirm anything property-specific with your local planning authority before finalising a size, since this guidance is general, not personalised advice.

Get Your Exact Size Confirmed With a Free Survey

Every bifold door sizes, width, height and panel figure in this guide is a starting point, not a final bifold door size answer for your own home. A free survey confirms your frame size based on your actual opening.

Send us your approximate opening width and height, a few photos, your floor plan if you have one, your preferred stacking side, and your glazing preference. We cover Buckinghamshire, Oxfordshire and the wider UK, with a 10-year guarantee on workmanship and materials. Book a survey, and we will turn these guide figures into your actual order size.