Aluminium Bifold Door Installation London & Surrey | Window Fitters Ltd

Aluminium Bifold Door Supply and Installation

Window Fitters Ltd supplies and installs aluminium bifolding patio doors for rear extensions, open-plan kitchens, and living spaces across Greater London, Surrey, and the South East. Bifold doors fold and slide flat against one wall, opening up the full structural width between your room and garden. Every doorset is manufactured to your exact opening dimensions using thermally broken aluminium profiles, fitted with stainless steel rolling gear, and fully compliant with Approved Document L insulation and Approved Document Q security standards.

How Bifold Doors Work Day to Day

A bifold doorset consists of multiple glass panels hinged together. One panel, called the traffic door, opens independently like a standard French door for everyday access without disturbing the other panels. When you want the full opening, you release the shootbolts on the remaining panels and slide the entire set along a bottom track, where they fold and stack flat against the wall.

Most residential bifold doors run on a bottom-rolling track system, where stainless steel wheels sit inside a recessed aluminium channel in the threshold. The top guide rail keeps the panels aligned but does not carry the weight. Some commercial systems use top-hung tracks where the panels hang from overhead rollers, keeping the floor track-free, but these require a significantly stronger lintel above.

Single-finger operation is realistic on a well-installed system. The panels should glide smoothly without forcing. If they feel stiff or gritty within the first year, the bottom track probably needs clearing of building debris or the rollers need adjusting.

Panel Configurations and Structural Widths

Aluminium bifold doors are available in 2-panel through to 7-panel configurations. The number of panels depends on your structural opening width:

Panels can fold inward or outward. Outward folding is more common because it keeps the stacked panels outside the room, freeing internal floor space. Inward folding suits properties where external space is limited, such as balconies or narrow patios.

The traffic door position matters for daily use. Place it at the end you approach most often from inside the house, typically the kitchen side. This saves opening the full set every time you step into the garden.

Thermal Insulation and Glazing Options

All aluminium bifold profiles use polyamide thermal breaks, a non-conductive plastic bridge between the inner and outer aluminium faces that prevents cold transfer through the metal frame. Combined with argon-filled low-E double glazing, most systems achieve a whole-door Ud of 1.3 to 1.5 W/m²K, satisfying Approved Document L. Compare thermal calculations in our U-value guide.

Glass options include:

• Standard low-E double glazing (28 mm units): The default for most residential installations. Balances thermal performance, weight, and cost.
• Triple glazing (44 mm units): Achieves Ud values down to 0.8 W/m²K. Heavier, which limits maximum panel width and requires heavier-duty rollers. Best suited to north-facing or exposed openings. See our triple glazing guide.
• Solar-control glass: Neutral metallic coating that reflects up to 70% of solar radiant heat while maintaining visible light transmission. Prevents south-facing living spaces from overheating in summer without resorting to curtains or blinds, assisting with Approved Document O compliance.
• Self-cleaning glass: Titanium dioxide coating that breaks down organic dirt in sunlight and sheets clean in rain. Practical for upper-floor or hard-to-reach installations.
• Acoustic laminated glass: PVB interlayer reduces external noise by 3 to 5 dB beyond standard double glazing conforming to Approved Document E sound standards. Useful if your garden backs onto a busy road.

All glass in bifold doors is toughened safety glass conforming to BS EN 12600, as required by Approved Document K for full-height glazed doors.

Threshold Types and Part M Compliance

The threshold is the bottom rail that the doors close onto. Two main types:

• Standard rebated threshold: A weather-rated aluminium sill with a raised upstand (typically 25 to 40 mm) that the door panels close against for maximum driving rain resistance. This is the most weather-tight option but creates a small step at the opening.
• Low-profile Part M threshold: A flush or near-flush sill with a maximum 15 mm upstand, designed for step-free wheelchair and pushchair access as required by Approved Document M. Slightly less resistant to driving rain, so external drainage (a linear channel drain just outside the threshold) is often specified to prevent water pooling. Check our Part M threshold guide.

Whatever threshold you choose, the bottom track must drain freely under Approved Document C moisture rules. Water enters the track through the panel gaskets during heavy rain and exits through weep slots at each end. If these slots block with dirt or leaves, water pools inside the track and can overflow onto your floor. Clearing the track twice a year prevents this.

Security Locking and Shootbolt Operation

Residential aluminium bifold doors use multi-point hook locking systems. The traffic door locks with a multi-point espagnolette handle engaging hook bolts into the frame head and sill. The remaining panels lock with internal top and bottom shootbolts that engage into the track and head rail.

The traffic door cylinder should be a 3-star TS007 anti-snap cylinder, tested to resist drilling, bumping, picking, and snapping attacks. This satisfies Approved Document Q (PAS 24) security requirements for ground-floor openings in new dwellings. View our door hardware and locking guide.

When locking up at night, always engage the traffic door handle fully (lift and turn) and check that each intermediate panel shootbolt has dropped into its floor keep. A panel that appears closed but has not engaged its shootbolt can be lifted out of the bottom track.

Colour Finishes and Dual-Colour Choices

Aluminium bifold frames are finished with polyester powder coating, a baked-on paint that resists UV fading, salt corrosion, and surface scratching. Standard colours available without extended lead times:

• Anthracite Grey (RAL 7016): The most popular finish for contemporary extensions. Explore our anthracite grey window and door guide.
• Jet Black (RAL 9005): A bold, modern finish often paired with dark brickwork or timber cladding.
• White (RAL 9010): Clean, traditional finish matching white uPVC windows elsewhere on the property.
• Custom RAL colours: Any RAL code can be specified, but custom colours add 1 to 2 weeks to manufacturing lead time and carry a colour surcharge.

Dual-colour finishes (one colour inside, another outside) are available on most systems, allowing you to match external brickwork while keeping a lighter interior frame.

Structural Opening Prep and Lintel Sizing

Bifold doors span wide openings, typically 3 to 6 metres. Under Approved Document A (Structure), the wall above must be supported by an engineered structural lintel capable of carrying the full masonry and roof load across that span. For openings wider than about 2.4 metres in masonry walls, this usually means a structural steel beam (RSJ) rather than a standard concrete lintel.

If you are creating a new opening as part of a kitchen extension, your architect or structural engineer will specify the steel beam size. If you are replacing existing patio doors with wider bifolds, our surveyor checks whether the existing lintel spans the full new opening width. If it does not, structural work is needed before the bifold can be fitted.

Our technical survey also checks:

• Reveal depth: How deep the brickwork opening is from the outer wall face to the plaster line. This determines whether the bifold frame sits flush with the outer wall, recessed into the reveal, or requires a sub-frame.
• Plumb and square: We measure the opening in three positions (top, middle, bottom for width; left, centre, right for height) to establish the true structural dimensions. The frame is manufactured with a 10 mm overall deduction to allow for expansion packing and plumb adjustment.
• Threshold and floor level: The finished floor level relative to the external patio slab determines threshold type and whether a step or ramp is needed for Part M compliance.

On-Site Fitting and Toe-and-Heel Alignment

A typical residential bifold installation takes one full working day for a 2-person glazier team (3 to 5 panels). Wider or more complex installations may extend into a second day.

• Existing doors or windows are removed carefully. If a structural steel beam is already in place, the opening is cleared and cleaned. If the old frame was load-bearing (which it should not be, but occasionally happens with poorly installed older patio doors), temporary props are placed before removal.
• The new outer frame is positioned in the opening, checked for plumb and level using a spirit level, and fixed to the masonry with heavy-duty frame fixings at 600 mm centres. Stainless steel fixings are used in exposed locations to prevent corrosion staining.
• Perimeter gaps between the frame and masonry are insulated with low-expansion polyurethane foam, then sealed externally with neutral-cure silicone conforming to Approved Document C to prevent water ingress.
• Individual glass panels are hung on the track, the rollers are adjusted for smooth gliding and correct panel alignment, and each panel is toe-and-heel glazed with load-bearing plastic packers placed behind the glass to brace the sash diagonally and prevent sash drop over time.
• All multi-point locks, shootbolts, and the traffic door cylinder are tested. Trickle vents are fitted if required by Approved Document F. The threshold drainage is checked by running water along the track.
• All packaging, offcuts, and protective film are cleared from site, leaving the doorset fully commissioned and weather-tight.

Pricing Factors on Bifold Projects

Bifold door pricing depends on several measurable factors. We do not publish fixed prices because every opening is different, but these are the variables that move the cost:

• Opening width and number of panels: More panels means more aluminium profile, more hardware, and more glass. A 3-panel set costs less than a 5-panel set.
• Glass specification: Upgrading from standard double glazing to triple glazing, solar control, or acoustic laminated glass increases the sealed unit cost per panel.
• Colour: Standard colours (Anthracite Grey, Black, White) are held in stock by most fabricators. Custom RAL colours and dual-colour finishes carry a surcharge and longer lead time.
• Threshold type: Low-profile Part M thresholds cost more than standard rebated thresholds and may require external drainage channels.
• Structural work: If the opening needs a new or wider steel beam under Document A, that is a separate structural cost on top of the bifold installation.
• Access: Ground-floor rear access with clear patio is straightforward. Restricted access, upper floors, or crane lifts for large panels add to installation time and cost.

For a detailed breakdown of pricing factors specific to London and Surrey, read our bifold door cost guide and explore our door systems overview.

Track Cleaning and Hardware Maintenance

Aluminium bifold doors need very little routine maintenance, but a few simple checks prevent the most common problems:

• Track clearing (twice yearly): Brush or vacuum dirt, leaves, and grit out of the bottom track channel. Blocked tracks cause stiff operation and can damage the roller wheels. Clear the weep drainage slots at each end of the track to prevent water pooling.
• Roller adjustment: If panels start to drag or sit unevenly, each panel has adjustment screws (usually accessible from the bottom edge) that raise or lower the rollers by a few millimetres. This corrects minor settlement or thermal expansion movement.
• Lock and handle lubrication: Apply light machine oil or silicone spray to the multi-point locking gear, hook bolts, and shootbolt mechanisms once a year. Never use heavy grease, which attracts dust and stiffens the mechanism over time.
• Cylinder care: On the traffic door anti-snap cylinder, use dry graphite powder, not WD-40 or oil, which gums the internal pin tumblers.
• Frame and gasket cleaning: Wipe aluminium frames with warm soapy water and a soft cloth. Avoid abrasive cleaners or solvents that can damage the powder coating. Wipe rubber gaskets to keep them flexible and airtight.
• Glass cleaning: Standard glass cleaner on both sides. If you have self-cleaning glass, avoid abrasive products that strip the titanium dioxide coating. For more general advice, view our fenestration troubleshooting guides.