Exterior and patio bifolds
Thermally broken, fully weather-sealed doors for the building envelope, with drained thresholds and multi-point locking. The most common type.
Door systems
Aluminium Bifold Doors
An aluminium bifold door is a row of glazed panels hinged together that fold and stack to one or both sides, opening almost the full width of a wall to a garden, terrace or street. Aluminium is the preferred frame material because its strength keeps sightlines slim and panels true at heights up to about 3 m. Metline supplies bifold door profiles and thermally broken sections in 6063 and 6061, with matching hardware, accessories and finishes, to door fabricators and project buyers worldwide.
- Panels
- 2 to 7+ per run
- Profile alloy
- 6063-T5 / T6, 6061-T6
- Frame depth
- about 60 – 120 mm
- Tests
- EN 14351-1 · BS 6375 · PAS 24
How an aluminium bifold door works
Each panel of a bifold door is joined to the next by hinges on alternate edges, so the panels fold like a concertina. Rollers on every second hinge line run in a track at the top or bottom of the frame and carry the weight, while guides keep the panels aligned. When fully open, the panels stack neatly at the side of the opening, typically occupying 70 – 100 mm of stack width per panel.
There are two main carrying principles. In a bottom-rolling system the weight runs on a stainless-steel or engineered-polymer track in the threshold, so the head of the frame need only guide the panels; this puts very little load on the lintel and is the usual choice for heavy glazed panels. In a top-hung system the panels hang from rollers in the head track, so the threshold can be almost flush and free of debris, but the structure above must carry the full door weight without deflecting more than a few millimetres.
Aluminium dominates the premium end of this market for three reasons. First, extruded 6063 profiles are stiff and strong enough to hold large double- or triple-glazed panels with frame-and-sash sightlines of around 110 – 140 mm where two panels meet, far slimmer than timber or uPVC. Second, aluminium does not swell, warp or creep, so the many hinges and rollers stay aligned for decades. Third, powder-coated or anodised aluminium needs little maintenance, even on coastal and high-UV sites.
Types of aluminium bifold doors
Slim-frame bifolds
Narrower interlocks and sashes for maximum glass. Usually limited to lighter panels or interior use unless the system is specially reinforced.
Interior glass bifolds
Non-thermal frames with single toughened or laminated glass to divide rooms, offices or hotel suites without losing light.
Commercial bifolds
Heavier profiles, high-cycle hardware, panic or anti-trap features and robust thresholds for restaurants, bars, shops and public buildings.
Corner bifolds
Two runs meeting at a corner with no fixed post, so the whole corner opens. Needs careful structural design above the opening.
Heavy-duty concealed-hinge bifolds
Deeper frames (often 100 mm+) with hidden hinges and tall panels, for villa and hospitality openings with large glass.
Bifold doors are also described by how the panels fold. They may open inward (panels stack inside the room, protected from weather, but taking floor space) or outward (panels stack on the terrace, keeping the room clear and making the door more weather-resistant because wind presses the sash onto its seals). They may fold all to one side, or split to both sides. Layouts are written as the number of panels folding to each side: 3L means three panels folding left, 2L2R means two to each side, 4L1R means four left and one right.
An odd number of panels allows a traffic door: the end panel works like an ordinary hinged door with its own lever handle, so you can step outside without opening the whole run. With an even number of panels folding to one side, the last panel is attached to a carrier and there is no independent door; a split layout such as 3L1R gives a traffic door on the single right-hand panel.
Popular bifold door sizes and panel counts
Bifold doors are almost always made to measure, but a few overall widths are very common. The number of panels follows from the width: most systems allow panels from about 600 mm to 1,000 – 1,200 mm wide, with 700 – 900 mm the comfortable range for weight, appearance and stacking.
| Overall width | Typical panels | Typical use |
|---|---|---|
| 1.8 – 2.1 m (6 – 7 ft) | 2 – 3 | Narrow openings, side doors, balconies |
| 2.4 m (8 ft) | 3 | Small patios and garden entrances |
| 3.0 m (10 ft) | 3 – 4 | The most common domestic size: kitchen or living room to garden |
| 3.6 m (12 ft) | 4 | Living rooms, garden rooms, extensions |
| 4.0 – 4.5 m | 4 – 5 | Villas, wide extensions |
| 5.0 – 5.5 m | 5 – 6 | Large homes, restaurants, hotel lounges |
| 6.0 m and above | 6 – 8+ | Commercial openings, showrooms; may be split into two stacks |
| Panel count | Approximate width range | Notes |
|---|---|---|
| 2 panels | about 1.2 – 2.4 m | Simple; no traffic door unless one panel is a hinged leaf |
| 3 panels | about 2.0 – 3.6 m | Traffic door possible; the classic garden door |
| 4 panels | about 2.8 – 4.5 m | Fold to one side or split 2 + 2 or 3 + 1 |
| 5 panels | about 3.5 – 5.5 m | Traffic door possible; wide view when closed |
| 6 panels and more | about 4.2 m upward | Often split to both sides to keep each stack manageable |
Heights of 2.1 – 2.4 m are standard; many aluminium systems allow up to about 2.7 – 3.0 m. Maximum panel size and weight (commonly around 100 – 150 kg per panel) are set by the system's hinges and rollers, not by the aluminium.
More panels are not automatically better. Each extra panel adds a vertical sightline, another set of hinges and rollers, and more stack width. Fewer, wider panels look cleaner but are heavier and need stronger hardware. The right answer balances opening width, single panel size, glass weight, opening direction and how much space the stack may take inside or outside.
Profile alloys, thermal breaks and frame depth
| Alloy & temper | Typical tensile / yield (EN 755-2 min.) | Use in bifold doors |
|---|---|---|
| 6063-T5 | 175 / 130 MPa (wall ≤ 3 mm) | Standard residential and light-commercial frames and sashes |
| 6063-T6 | 215 / 170 MPa | Taller panels, wider panels and higher wind loads |
| 6060-T66 | 215 / 160 MPa | European alternative to 6063 for window and door systems |
| 6061-T6 / 6005A-T6 | 260 / 240 MPa; 270 / 225 MPa (thin walls) | Reinforcing sections, heavy-duty tracks and posts for very large panels |
6063 is the default alloy for door systems because it extrudes into complex thin-wall, multi-chamber shapes with precise tolerances (EN 12020-2 for precision profiles) and a smooth surface that powder coats and anodises evenly. Main frame walls are typically 1.6 – 2.5 mm, with thicker walls at hinge and roller fixings. 6061 or 6005A is used only where calculations show 6063 is not stiff or strong enough, as in heavy-duty tracks, corner posts or steel-replacement reinforcements.
For exterior doors, the inner and outer aluminium shells are joined by polyamide thermal break strips (glass-fibre reinforced PA66), commonly 20 – 34 mm wide, inserted and rolled in place. The break interrupts the heat path through the metal, raises the inside surface temperature and prevents condensation on the frame. Frame depths of about 60 – 80 mm are typical for double glazing in temperate climates; 90 – 120 mm frames carry triple glazing and wider breaks for cold climates and low-energy buildings.
- Corner joints: mechanically crimped or pinned with aluminium corner cleats and sealed with structural adhesive, so the sash stays square under the weight of the glass.
- Multi-chamber sections: extra internal chambers raise bending stiffness and lengthen the heat path.
- Interlock design: the meeting profiles between panels carry gaskets and are where most air leakage and water entry happen, so their design matters as much as the frame depth.
Weather, thermal, acoustic and security performance
Bifold doors are declared and compared by test results, not by marketing descriptions. Ask for the test report for the configuration you are buying, because panel size, opening direction and threshold type all change the result.
| Property | European / UK standard | Typical classes for a good exterior bifold | North America |
|---|---|---|---|
| Air permeability | EN 12207 (via EN 1026) | Class 3 – 4 | NAFS air leakage; ASTM E283 |
| Watertightness | EN 12208 (via EN 1027) | Class 4A – 7A; lower for low thresholds | NAFS water test; ASTM E547 / E331 |
| Wind-load resistance | EN 12210 (via EN 12211) | Class B3 – C5 (1,200 – 2,000 Pa test pressure) | NAFS performance grade; ASTM E330 |
| Weathertightness (UK) | BS 6375-1 | Exposure category to suit site | — |
| Operation and strength | BS 6375-2, EN 13115, EN 1191 cycling | Operating forces class 1 – 2; durability by cycles | NAFS operating force |
| Thermal transmittance | EN ISO 10077-1/-2, EN ISO 12567-1 | Uw about 1.2 – 1.8 W/m²K with double glazing; below 1.0 with triple | NFRC 100 U-factor |
| Acoustic insulation | EN ISO 10140, EN ISO 717-1 | Rw about 30 – 38 dB depending on glass | STC / OITC |
| Burglar resistance | PAS 24 (UK), EN 1627 RC2 – RC3 | PAS 24 for new UK homes (Approved Document Q) | ASTM F476 / F842 |
The product standard EN 14351-1 brings these results together into the declaration of performance needed for CE or UKCA marking. In England, Approved Document L requires replacement glazed doors in existing dwellings to reach a U-value of 1.4 W/m²K or better, and Approved Document M limits threshold upstands for level access on new homes, which affects the choice between a flush and a weathered threshold.
Glass is specified separately: insulating glass units to EN 1279, toughened safety glass to EN 12150, laminated glass to EN 14449 and safe glazing in critical locations (doors and low glazing) per BS 6262-4 or local codes. In the US, glazing in doors must meet the safety-glazing rules of 16 CFR 1201.
Glazing options for bifold doors
| Glazing | Typical build-up | When to use it |
|---|---|---|
| Double-glazed IGU | 4 – 6 mm toughened + 16 – 20 mm argon cavity + 4 – 6 mm toughened, Low-E coating, warm-edge spacer | Standard for homes in temperate climates; 24 – 28 mm units |
| Triple-glazed IGU | for example 5 + 12A + 5 + 12A + 5 mm, two Low-E coatings | Cold climates, passive-house targets, quieter rooms; 40 – 50 mm units need deeper frames |
| Wide-cavity double IGU | for example 5 + 27A + 5 mm | Heavy-duty deep systems; good thermal and acoustic balance |
| Laminated or laminated-toughened | 6.4 – 8.8 mm laminated in one or both panes | Security, safety where breakage must not leave an opening, acoustic control |
| Solar-control Low-E | Selective coating on surface 2 | South- or west-facing glass in hot climates to cut solar gain |
| Obscure, tinted, decorative | Patterned, acid-etched or tinted pane in the IGU | Privacy, bathrooms, commercial branding |
| Single toughened or laminated | 8 – 10 mm | Interior partitions only |
Glass weight is the main driver of panel weight: each square metre of 4 + 20 + 4 mm double glazing weighs about 20 kg, and a triple unit with three 5 mm panes about 37.5 kg. A 900 × 2,400 mm triple-glazed panel therefore carries around 80 kg of glass before the frame is counted, so heavy glass must be matched to hinges and rollers rated for it.
Hardware, thresholds, seals and drainage
Hinges
Stainless-steel or aluminium hinges, surface-mounted or concealed, rated for panel weight. Adjustable hinges allow fine alignment after installation.
Rollers and tracks
Twin-wheel or four-wheel stainless-steel or polymer roller carriages on a stainless track; sealed bearings for coastal sites.
Locks and handles
Multi-point locks with hook bolts or shoot bolts into head and threshold; key-locking lever handle on the traffic door; flush handles on intermediate panels.
Safety features
Anti-finger-trap gaskets between panels, soft-close or damped stops, and panel restraints for windy sites.
Seals
Co-extruded EPDM gaskets in the frame, sash and interlock; brush seals only where the threshold must be very low.
Insect screens
Pleated or retractable screens that slide across the opening without blocking the stack.
| Threshold type | Upstand | Pros and cons |
|---|---|---|
| Flush / low threshold | about 0 – 15 mm | Level access and a seamless floor; lower watertightness, best under a canopy or with an external drainage channel |
| Rebated weathered threshold | about 30 – 50 mm | Best rain resistance and air tightness on exposed elevations; small step |
| Recessed / sunken track | set into the floor | Flush finish with drainage below; needs coordination with the screed and waterproofing |
| Hidden-drainage threshold | varies | Drains water from the track through concealed outlets for a clean look |
On exposed sites, combine a weathered threshold with an outward-opening layout and a linear drain outside the door. Low thresholds work well under a canopy, veranda or pergola where wind-driven rain is unlikely. Whichever is chosen, the sill must be laid perfectly level and supported along its full length; most bifold problems in service trace back to an uneven threshold or a deflecting lintel.
Colours and surface finishes
| Finish | Typical standard | Typical film thickness | Best for |
|---|---|---|---|
| Polyester powder coating | EN 12206-1, Qualicoat class 1, AAMA 2603 / 2604 | 60 – 80 µm | Homes and general projects; any RAL colour, matt to gloss |
| Super-durable powder | Qualicoat class 2, AAMA 2604 | 60 – 80 µm | High UV and long colour-retention targets |
| PVDF (fluoropolymer) coating | AAMA 2605, Qualicoat class 3 | about 25 – 40 µm (2 – 3 coats) | Coastal sites, high-rise facades, long warranties |
| Anodising | EN ISO 7599, Qualanod, AAMA 611 | 15 – 25 µm (class 15 – 25) | Metallic silver, bronze, champagne and black |
| Wood-grain transfer | Sublimation over powder base coat | as base powder | Timber look with aluminium durability |
| Dual colour | Different powder inside and out, split at the thermal break | 60 – 80 µm | Exterior to match the facade, interior to match the room |
Anthracite grey (RAL 7016), jet black (RAL 9005), traffic white (RAL 9016) and textured dark greys are the most specified colours for contemporary homes; bronze and champagne anodised finishes suit commercial buildings. Dual-colour frames are possible because the thermal break separates the inner and outer shells, which are coated before assembly. For coastal sites within a few kilometres of the sea, specify a seaside-grade pretreatment (such as Qualicoat Seaside) or PVDF, and stainless-steel hardware.
- Approve a physical colour sample and gloss level before production; screen colours are not reliable.
- For large projects, ask for batch colour control and coating-thickness readings.
- Specify protective film on finished profiles until installation is complete.
What affects the price and how to order
- MeasureGive the structural opening width and height, wall construction, floor finish level and whether the lintel can carry a top-hung system.
- ConfigureChoose panel count and layout (e.g. 3L or 3L2R), opening direction, traffic door position and threshold type.
- SpecifyGlazing build-up, colour inside and out, hardware finish, screens and any performance class, U-value or security standard required.
- ConfirmWe return a profile and accessory list, section data for the chosen series and a quotation on EXW, FOB, CIF or DAP terms.
- DeliverProfiles are film-protected, edge-protected and bundled or crated, with hardware packed and labelled by opening for your fabricator.
Bifold doors or sliding doors?
| Factor | Aluminium bifold door | Aluminium sliding door |
|---|---|---|
| Clear opening | About 90 % of the frame width | About 50 – 67 % for two- or three-track designs, unless pocketed into the wall |
| View when closed | More vertical sightlines | Fewer, wider panes; uninterrupted views |
| Space needed | Room for the stack to fold inside or outside | None beyond the frame |
| Daily use | Traffic door for quick access; fully open on fine days | One panel slides for everyday use |
| Weather performance | Very good with weathered threshold; more joints to seal | Very good; fewer joints, lift-and-slide gives excellent sealing |
| Maximum panel size | About 1.2 × 3.0 m | Lift-and-slide panels up to several metres wide |
| Typical cost | Higher per metre (more hardware) | Lower for standard slides; high for large lift-and-slide |
Choose a bifold when you want the opening to disappear completely in good weather, for example where a kitchen and terrace become one space. Choose a sliding or lift-and-slide door when the view matters more than full opening, the opening is very wide, or there is nowhere for a stack to go.
References and standards
- EN 14351-1 – Windows and doors: product standard, performance characteristics
- EN 12207 / EN 12208 / EN 12210 – Air permeability, watertightness and wind-load resistance classification
- BS 6375-1/-2/-3 – Performance of windows and doors: weathertightness, operation and strength
- PAS 24 – Enhanced security performance requirements for doorsets and windows in the UK
- EN 12206-1 – Coatings of aluminium for architectural applications: powder coatings
- UK Government – Approved Document L, Conservation of fuel and power
Aluminium (aluminum) bifold doors: FAQ
How many panels should my bifold door have?
Divide the opening width by a comfortable panel width of about 700 – 900 mm. A 3 m opening usually takes three or four panels; 4 m takes four or five. Choose an odd number if you want a traffic door on one side.
Should bifold doors open inward or outward?
Outward-opening doors are generally more weather-resistant and keep the stack out of the room. Inward opening keeps panels away from rain and terrace furniture and suits balconies. Choose based on the space on each side and exposure to wind and rain.
What is the maximum size of an aluminium bifold door?
Runs of 6 – 8 m or more are possible by adding panels or splitting to both sides. Individual panels are usually limited to about 1.0 – 1.2 m wide and 2.7 – 3.0 m high, depending on the system hardware.
Are aluminium bifold doors secure?
Good systems use multi-point locks, internally beaded or bonded glass, anti-lift features and laminated glass. In the UK, look for PAS 24 test evidence; in Europe, EN 1627 resistance class RC2 or above.
Which aluminium alloy is used for bifold door profiles?
6063 in T5 or T6 temper for frames and sashes, sometimes 6060-T66 in Europe, with 6061-T6 or 6005A reinforcement for very large or heavy panels.
Do low thresholds leak?
A flush threshold has lower watertightness than a rebated one. It works well under a canopy or with an external drain; on exposed elevations, a weathered threshold is the safer choice.
Does Metline supply complete bifold doors?
No. We supply thermally broken bifold profiles, hardware and accessories, cut and machined to drawing on request; your fabricator glazes and assembles the doors. Export packing is available to any destination.
Planning aluminium bifold doors?
Send the openings, panel layout, glazing and finish. Our team will propose a profile series and quote profiles and hardware delivered to your site.
