Bi Fold Door Sizes UK: Choosing the Right Opening & Configuration
There is no single standard bi fold door size in the UK. External bifold systems are sold in a range of complete frame widths, heights and panel configurations, so the correct choice depends on the structural opening you have or plan to create. The most important distinction is between a nominal description such as 6ft or 8ft and the exact metric frame dimension shown for the product.
This guide explains bi fold door sizes UK buyers are likely to compare, how frame size relates to structural opening size, what panel count changes, and how threshold, handing and stacking space affect the final choice. Browse our bi fold doors and use the exact product dimensions as the final reference.
Nominal Size vs Exact Bi Fold Frame Size
A product can be described as 6ft, 8ft or 10ft for convenience, but those labels should not be used as construction dimensions. The actual frame width, height and depth are stated in millimetres and are the figures the builder and installer need.
Always give the structural team the exact product information plus the manufacturer's required fitting tolerance.
Example Bi Fold Door Sizes at JJ Building Materials
The LPD Doors AluVu 6ft Aluminium Bi Fold Door is listed at 2128 x 1790 x 70mm. The LPD Doors AluVu 8ft Aluminium Bi Fold Door is listed at 2128 x 2390 x 70mm, while the LPD Doors AluVu 10ft Aluminium Bi Fold Door is listed at 2128 x 2990 x 70mm.
These current metric dimensions are much more useful for opening design than the nominal feet labels.
What Does Bi Fold Door Size Refer To?
For a complete external bifold system, size normally refers to the outside dimensions of the doorset frame, although you should always check the individual listing. It is not the clear opening, the glass size or the width of one panel.
The structural aperture in the building must be larger than the frame by the fitting tolerance required by the manufacturer.
How Wide Should a Bi Fold Door Opening Be?
The opening should suit the exact frame plus the approved installation space. If the wall has not yet been built, select the doorset first and form the opening around that system. If the opening already exists, measure it at the top, centre and bottom and compare those figures with the product.
Use our how to measure for bi fold doors guide before ordering.
How High Are Bi Fold Doors?
Residential external systems commonly sit around patio-door heights, but there is no universal height. The frame, threshold and cill arrangement determine the installed requirement. For example, the current AluVu examples above list a height of 2128mm, but that should not be treated as a standard for all brands or future ranges.
Measure from the agreed structural base or threshold datum to the underside of the head at several points.
Frame Depth Matters Too
Width and height receive most attention, but frame depth affects how the doorset sits within the wall reveal and how internal and external finishes meet it. The current AluVu examples above list a 70mm dimension in the product title.
Check how that depth works with brickwork, render, cladding, internal plaster and the intended frame position.
Panel Count and Overall Width
As overall frame width increases, the doorset may use more panels. The manufacturer determines which panel counts and configurations are available for each size. Do not divide an opening by an arbitrary panel width and assume a custom configuration can be created.
Panel count affects the appearance when closed, the size of the glazed areas and how much space the folded stack occupies when open.
Why Panel Proportions Matter
Very wide panels can be heavy and require appropriate hardware, while very narrow panels can create more frame lines across the view. The system designer balances panel proportions with structural and operational requirements.
Choose from the configurations offered for the product rather than trying to force a preferred panel count into a frame size that was not designed for it.
Odd vs Even Panel Configurations
Some systems use an odd number of leaves to create a convenient traffic door, while even-panel arrangements can fold differently. The user experience can therefore vary even between doorsets of similar overall width.
Review the configuration diagram to understand which panel opens first and how the remaining leaves stack.
What Is a Traffic Door?
A traffic door is a panel that can operate more like a conventional hinged door for everyday access without folding the entire set. If frequent garden access matters, the position of the traffic door can be as important as the overall frame size.
Check which sizes and handings provide the required traffic-door arrangement.
Stacking Space
When the panels are fully open, they fold together and project into the chosen side of the opening. The wider the individual leaves and the more panels in the stack, the more space that folded bundle can occupy.
Measure nearby walls, downpipes, furniture, planters, kitchen units, steps and patio features before choosing the configuration.
Inward vs Outward Opening
Outward-opening bifolds preserve more internal floor space but need clear patio or garden area. Inward-opening panels do the opposite. The available opening direction is product-specific.
Think about curtains, blinds, radiators, furniture, exterior drainage and steps rather than choosing solely from appearance.
Left- and Right-Hand Bi Fold Door Sizes
Some doorsets have left- and right-hand variants in the same overall size. Handing can determine the traffic door or stack direction. Use the exact manufacturer's viewpoint and diagram because the meaning of left and right can differ between suppliers.
A size that physically fits is still wrong if the panel arrangement conflicts with the room or garden layout.
Threshold Height and Floor Build-Up
The opening height should be coordinated with the final internal floor. Screed, insulation, underfloor heating, tiles, adhesive and other finishes can all alter the available height.
Set a threshold datum early so the builder, flooring contractor and door installer work to the same level.
External Paving and Drainage
External paving should be planned alongside the threshold. A visually flush transition can be attractive, but water still has to be managed correctly. Do not raise patio levels in a way that blocks drainage routes or compromises the weathering detail.
Record the intended external level when measuring for the doorset.
Creating a New Opening for Bi Fold Doors
Widening an external wall is a structural project. The support above the opening, bearings, wall construction and anticipated deflection need to be considered. The selected frame should not be asked to carry structural loads from the wall above.
Choose the doorset early and coordinate the exact required aperture with the structural design.
Replacing French or Sliding Patio Doors
An existing French-door or sliding-door frame may hide a larger structural aperture than the visible opening suggests. If the new bifold frame is the same general width, the old frame still needs to be removed or surveyed carefully to confirm the true space.
If you plan to widen the opening, do not order the bifold system until the structural design and final aperture are confirmed.
Stock Size vs Made-to-Measure Decisions
Stock-size doorsets can be efficient when the opening can be created or adjusted to suit them. If an existing opening is significantly different, forcing a stock frame into the wrong size with excessive packing is not a good solution.
Compare the cost and disruption of altering the opening with other available door sizes before deciding.
Can Aluminium Bi Fold Doors Be Trimmed?
No. A complete aluminium doorset should not be treated like a timber door leaf that can be planed down. The frame contains profiles, joints, drainage, glazing and hardware that are manufactured to a specific size.
Order the correct frame or adjust the structural opening appropriately.
Bi Fold Door Size and Clear Opening
The clear opening when the panels are folded is less than the structural opening because the frame and stacked panels still occupy space. If maximising the open width is important, compare the configuration and stack arrangement rather than judging only by the outside frame width.
Ask for product-specific drawings if the usable clear opening is critical to the design.
Size Planning for Extensions
For a new extension, coordinate the bifold size with kitchen layouts, structural columns, wall returns and furniture. A wider opening is not automatically better if it removes useful wall space or forces the stack into a circulation route.
Think about how the room will work with the doors closed in winter as well as fully open in summer.
Create a Bi Fold Door Schedule
For a project with more than one glazed opening, record the room, structural aperture, chosen frame size, panel count, handing, traffic door, opening direction, colour, threshold level and installer. This helps prevent similar-sized products being allocated to the wrong opening.
Include final floor and external paving levels on the same schedule.
Bi Fold Door Size Checklist
- Exact frame height and width.
- Frame depth.
- Structural opening measured at multiple points.
- Manufacturer fitting tolerance.
- Both diagonals checked.
- Base and head level checked.
- Finished internal floor level.
- Threshold and external drainage design.
- Panel count and proportions.
- Traffic door position.
- Left/right handing.
- Inward/outward opening.
- Stacking clearance.
- Structural support above.
Frequently Asked Questions
What is the smallest standard bifold door size?
There is no universal smallest external bifold size. Available dimensions depend on the manufacturer and system. Compare the actual products offered.
Are 6ft bifold doors exactly 6ft wide?
Not necessarily. The feet description is often nominal. Use the exact metric frame width shown on the product page for construction planning.
How many panels do I need for a 3m opening?
Panel count depends on the configurations offered for the chosen system. Select a product whose complete frame size and panel arrangement suit the opening.
Can I build the opening before choosing the doors?
You can, but choosing the doorset first is usually more efficient because the opening can be formed to the exact required frame size and tolerance.
Can bifold doors be made smaller on site?
No. A complete aluminium frame should be ordered in the correct size or the structural opening should be designed to suit it.
Does the threshold add to the overall height?
It depends on the product and how the dimensions are stated. Check the individual technical information and installation instructions.
Choose the Right Size Bi Fold Doors
Compare exact dimensions in our aluminium bi fold door range, then use our bi fold doors buying guide for glazing, colour, threshold and configuration advice.