What are the sightlines on a bifold vs sliding door?

Bifold meeting stiles are typically 90-120mm wide where two panes meet (45-60mm per pane × 2). Sliding door interlocks range from 20mm (Cortizo Vision, APX20 Plus) to 50mm (standard slider). Visually, that's the difference between a window-like view and a clearly framed view. For maximum visible glass when closed, sliding wins by a large margin.

Can bifolds have a flush threshold?

Yes. APX X-Fold 120, Schüco AS FD 75, and Visofold 1000 all offer a low-threshold or flush-threshold option that drops the rail to 22-35mm above floor level, wheelchair-friendly and visually seamless. The trade-off is reduced weather resistance: flush thresholds are typically rated to lower water-tightness classes than the standard raised threshold (PA Class 9A vs Class 6A).

Bifold vs Sliding Doors 2026 | Which One, and What It Costs

Q: Are bifold doors going out of style?

No, but the market has split. Bifolds remain dominant for narrower openings (under 4m) where you want to fully fold the entire span back. For wider openings on contemporary builds, the trend since 2022 has been toward slim sliding doors, Cortizo Vision, APX20 Plus, because the closed-state sightline is so much cleaner. Both are still being specified by London architects in 2026; bifolds are not dead, just no longer the default.

Q: Do sliders open as much as bifolds?

No. A standard 3-pane sliding door opens roughly 2/3 of the span (one pane slides behind two fixed). A 3-pane bifold folds back to 95%+ of the span clear opening. The compromise is pocket sliders (slide into the wall cavity) which open 100%, or 4-pane lift-and-slide systems that can open one full half. If full-span opening is non-negotiable, bifold still wins.

Q: Which is more thermally efficient, bifold or sliding?

Sliding doors typically achieve 1.3-1.0 W/m²K whole-door U-value with double glazing. Bifolds typically achieve 1.4-1.6 W/m²K. The difference comes from the meeting stiles, every bifold pane has two stiles meeting another pane, doubling the thermal break complexity. Schüco AS FD 90 closes the gap at 1.3 W/m²K, but slim sliders like Cortizo Vision (1.3 W/m²K) and Schüco ASE 80.HI (0.84 W/m²K with triple glazing) lead overall.

Q: Which is cheaper, bifold or sliding doors?

Sliding doors usually win on price for the same opening width. A 3m × 2.1m 3-pane sliding door fits at £4,500-£9,000 (APX20 Plus) vs £6,000-£12,000 for a 3-pane bifold (X-Fold 120, Schüco AS FD 75). Sliders have fewer moving parts, fewer hinges, and simpler hardware. Bifolds get more expensive faster as panes are added because every additional pane adds two hinges and a meeting stile.

Q: How wide can sliding and bifold doors go?

Bifolds can run almost indefinitely, 7-pane configurations spanning 7m+ are common, limited mainly by the structural opening rather than the door. Sliding doors are usually capped at 4-pane straight runs (around 6m) or larger if pocket-sliding (slides into the wall). For openings over 6m, bifold and pocket-slide are the two practical options.

Q: Which is more secure, bifold or sliding?

Both can meet PAS 24:2022 with multi-point locking. Sliding doors with hook-bolt mechanisms (Cortizo Vision, Schüco ASE 60 RC) are arguably harder to force because there's only one moving pane to compromise; bifolds have a master door and slave panes, with the master being the key entry point. In practice, both are very secure and home insurance treats them equivalently.

Q: Bifold or sliding for a small London garden?

For typical London terrace/semi gardens (3-4m opening, under 7m garden depth), slim sliding doors usually look better year-round, the 20mm interlock keeps the view clean even in winter when doors stay closed. Choose bifolds if you genuinely entertain outdoors weekly in summer and need full-span opening; choose sliding if the door is closed 80%+ of the year and the view matters more than the opening.

The honest, installer-side truth

Both products work. Both have a place. The pattern across our London projects is consistent: bifolds win for opening wide and entertaining; sliding wins for the view through the glass. If your door spends most of the year closed, you will notice a bifold's meeting stiles, published at 90 to 122mm depending on system. If it spends the summer open, you will notice that a slider only ever opens part of the span.

Sightline comparison

When the doors are closed, which in London is most of the year, the width of the vertical section where two leaves or panes meet determines what you actually see. Every figure below is the manufacturer's own published dimension.

System	Type	Published section where leaves meet
APX20 Ultra Slim (Cortizo COR Vision Sliding)	Sliding	20 mm central junction
APX20 Plus (Cortizo COR Vision Plus Sliding)	Sliding	25 mm central junction
Schüco ASE 60 / ASE 80.HI	Lift-and-slide	40 mm Design Line, otherwise 102 mm
APX47 (Cortizo 4700 Sliding)	Sliding, large pane	50 mm sash
Schüco AS FD 75 / AS FD 90.HI	Bifold	90 or 104 mm at the vent joint
APX Fold	Bifold	122 mm typical sightline

Opening behaviour

Same structural opening, completely different open-state experience. This is where bifolds reclaim ground sliders cannot match. Figures below are the geometry of the configuration, not a manufacturer specification.

Configuration	Roughly how much opens	Open behaviour
2-pane sliding (1 fixed, 1 sliding)	About half	One pane slides behind one fixed
3-pane sliding (2 fixed, 1 sliding)	About a third	One sliding pane passes in front of two fixed
4-pane sliding (2-track)	About half	Two panes slide behind two fixed
Pocket slider	Nearly all	Panes slide into a cavity in the wall
3-leaf bifold	Nearly all	Concertina-folds and stacks clear to one side
5 or 7-leaf bifold	Nearly all	Concertina-folds, stacked to one side or split
Lift-and-slide (Schüco ASE)	About half	Sash lifts onto rollers, slides, then settles back onto its seals

Threshold options

A low or level threshold is on most architect drawings now. Both bifold and sliding systems offer one, and each manufacturer publishes its own threshold height and its own weather rating, so the honest way to compare is system by system rather than by a generic rule.

System	Published threshold	Published weather rating
Schüco AS FD 75 bifold	From under 12.5 mm	Class 4 air / E750 water / C3 wind
Schüco ASE 60 lift-and-slide	Under 12.5 mm	Class 4 air / E900 water / C5 wind
APX Fold bifold	Low threshold option	Kitemark certified, PAS 24 available
APX20 Plus sliding	Recessed or flush track option	Class 4 air / 9A water / C4 wind
APX20 Ultra Slim sliding	Level threshold	Watertightness Class 7A

Water and wind classes are to BS EN 12208 and BS EN 12210. A lower threshold generally trades away some watertightness, which is why the class is quoted alongside it rather than on its own.

What these doors cost

Both bifolds and sliding doors are made to order, so a fitted price depends on the structural opening, the number of leaves or panes, the glass specification, the threshold detail, the colour and site access. We price after a survey rather than from a list. As a rule of shape rather than a quotation: a bifold gets more expensive faster than a slider as leaves are added, because every additional leaf brings hinges, a running carriage and another meeting stile. Every Apex quote covers the frame, glazing, fitting, removal of the existing door, FENSA self-certification under Reg 40373 and our 10-year guarantee.

The verdict, when each wins

Use this as your decision shortcut. If you tick more rows on one side, that's your answer.

When to choose Bifold	When to choose Sliding
You entertain outdoors weekly in summer	Doors stay closed 80%+ of the year
You need 90%+ open-span clearance	You want maximum visible glass when closed
Opening is over 6m wide (5+ panes)	Opening is 2-4m wide (sweet spot)
Indoor-outdoor living is the brief	Modern minimalist aesthetic is the brief
Garden views are short (under 7m depth)	Garden views are long or you want a clear sightline
Children or pets need wide unobstructed access	Acoustic isolation matters (sliding published up to 43 dB Rw)
You want the whole span to open	You want the least frame in the view
You don't mind a 90-122mm sightline where leaves meet	A 20 or 25mm junction is your priority

Specifying the right system

For most London projects we end up recommending one of these systems. Each is matched to a typical brief, with the manufacturer's own published figures.

Brief	Recommended	Why
Standard 3m garden bifold	APX Fold	Leaves to 1200 × 2500mm, 122mm sightline, Uw from 1.4 W/m²K, PAS 24 available
Wide bifold across a whole elevation	Schüco AS FD 75	Up to 7 leaves across 10.5m, leaves to 1500 × 3000mm at 150kg, Uw from 1.1 W/m²K
Best thermal performance in a bifold	Schüco AS FD 90.HI	Uw from 0.8 W/m²K, leaves to 3500mm high, Rw up to 47 dB, RC2 available
Narrowest sliding junction	APX20 Ultra Slim	20mm central junction, 37mm sash, sashes to 2500 × 3000mm at 320kg
Large sliding panels	APX20 Plus	25mm junction, sashes to 4000 × 4000mm, 400kg by hand or 700kg motorised, Uw from 0.9
Lift-and-slide for very heavy sashes	Schüco ASE 80.HI	Uw from 0.99 W/m²K, 3500 × 3500mm at 500kg, up to RC3, threshold under 12.5mm

Frequently asked

Are bifold doors going out of style?

No, but the market has split. Bifolds remain the answer wherever you genuinely want the whole span to open. On wider contemporary builds, slim sliding doors have taken ground since the early 2020s because the closed-state sightline is so much cleaner, 20 or 25mm at the junction against 90 to 122mm where two bifold leaves meet. Both are still specified by London architects. Bifolds are not dead, they are just no longer the default.

Do sliders open as much as bifolds?

No. A sliding door only ever opens the part of the span that its moving panes cover, so a typical three-pane slider with two fixed panes opens about a third, and a two-track four-pane opens about half. A bifold concertinas and stacks clear, so nearly the whole span opens. If full-span opening is non-negotiable, the choice is a bifold, or a pocket slider that runs the panes into a cavity in the wall.

Which is more thermally efficient, bifold or sliding?

On published figures, the best sliders and the best bifolds are closer than the old rule of thumb suggests. Schüco publishes Uw from 0.8 W/m²K for the AS FD 90.HI bifold and from 1.1 W/m²K for the AS FD 75. On sliding, Cortizo publishes from 0.9 W/m²K for COR Vision Plus Sliding (Apex APX20 Plus) and from 1.3 W/m²K for COR Vision Sliding, and Schüco publishes from 1.1 W/m²K for the ASE 60 and from 0.99 W/m²K for the ASE 80.HI. Compare the specific systems, not the categories.

Which is cheaper, bifold or sliding doors?

Both are made to order, so we price after a survey rather than from a list. The reliable pattern is how the cost scales: a bifold gets more expensive faster than a slider as the opening widens, because every extra leaf adds hinges, running gear and another meeting stile, whereas a slider adds a pane and a track. For the same opening width, that usually favours the slider.

What are the sightlines on a bifold vs a sliding door?

Schüco publishes a face width at the vent joint of 90 or 104mm for both the AS FD 75 and the AS FD 90.HI. Apex's APX Fold publishes a typical sightline of 122mm. On sliding, Cortizo publishes a 20mm central junction for COR Vision Sliding and 25mm for COR Vision Plus, and Schüco publishes an interlock face width of 40mm on the ASE Design Line. Visually that is the difference between a clearly framed view and something close to an uninterrupted one.

Can bifolds have a low threshold?

Yes. Schüco publishes threshold heights of 4, 15 and 71mm for the AS FD 75 and AS FD 90.HI, so a genuinely low threshold is available, and APX Fold offers a low threshold option. The trade-off is weather rating: Schüco publishes the AS FD 75 at Class 4 air, E750 water and C3 wind, where its ASE lift-and-slide is published at Class 4, E900 and C5. Compare the published class alongside the threshold height rather than treating them separately.

How wide can sliding and bifold doors go?

Schüco publishes a maximum unit width of 10.5m across up to seven leaves for the AS FD 75 bifold, and 21m for the ASE lift-and-slide as a complete unit in single, double or triple track. Individual sashes matter as much as the total: Schüco publishes 3500 × 3500mm at up to 500kg for ASE, and Cortizo publishes 4000 × 4000mm at 400kg by hand for COR Vision Plus Sliding.

Which is more secure, bifold or sliding?

PAS 24 is available on both. Schüco publishes RC2 to BS EN 1627 for the AS FD 75 and AS FD 90.HI bifolds, up to RC2 for the ASE 60 and up to RC3 for the ASE 80.HI. Cortizo publishes a passed PAS 24 security test across its sliding range. In practice both types are secure when specified properly, and PAS 24 needs to be written on the quote rather than assumed.

Bifold or sliding for a small London garden?

For a typical terrace or semi with a 3 to 4m opening and a short garden, a slim slider usually looks better year-round, because a 20 or 25mm junction keeps the view clean through the months the doors stay shut. Choose a bifold if you genuinely entertain outdoors and want the whole span clear. Choose sliding if the door is closed most of the year and the view matters more than the opening.

Bifold vs Sliding Doors