Everything You Need to Know About Bifold Doors
Bifold doors have become one of the defining features of the London kitchen extension — and for good reason. When the weather is good and the doors are fully open, they dissolve the barrier between inside and outside and transform how the space feels. Here's a comprehensive guide to specifying, procuring, and installing bifold doors — and the questions to ask before you commit.
How Bifold Doors Work
Bifold doors consist of multiple panels connected by hinges. When opened, the panels fold against each other (accordion-style) and slide on a top-hung or bottom-rolling track to stack at one or both sides of the opening. The result is a fully open aperture — wider than any conventional door or window could provide — with the folded panels occupying a zone at one or both ends of the opening.
Panels typically come in widths of 700–1000mm. A typical 3-metre opening might be served by three panels; a 4-metre opening by four panels; a 5-metre opening by five or six panels. An even number of panels allows folding to both sides; an odd number typically folds predominantly to one side. Most bifold configurations include at least one panel that opens as a conventional door (the "traffic door") without opening the whole set — useful for everyday use when you don't want the full opening.
Frame Material
Thermally broken aluminium is the dominant choice for bifold doors in London extensions. Slim sightlines, excellent durability, low maintenance, good thermal performance, and wide colour availability make it the most practical and aesthetically appropriate choice for the majority of contemporary extension designs.
Timber and timber-aluminium composite systems are also available and appropriate for more traditional designs, but require periodic maintenance and are more expensive.
Glazing Specification
Specify double glazing as a minimum (4-16-4mm configuration with low-e glass and argon fill), and consider triple glazing where energy performance is a priority. Solar control glass is strongly recommended for south-facing or west-facing orientations — it limits solar heat gain in summer while maintaining daylight transmission.
Structural Requirement
The opening for bifold doors requires a structural lintel or steel beam to carry the load above. This is a non-negotiable structural requirement and must be specified by the structural engineer. The size of the beam required depends on the width of the opening and the load above it — for wide openings, this can be a substantial steel section.
Budget Guide
Aluminium bifold doors (supply only): £1,500–£5,000 for a 3-panel set; £2,500–£8,000 for a 4–5 panel set, depending on specification and supplier. Installation (by a specialist glazing contractor): £500–£1,500 per set. The structural opening (beam and structural works) is a separate cost — typically £3,000–£8,000 for the structural element of a full-width opening.
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