Short answer: choose bifold doors if you want to open almost the whole width of your extension to the garden and you use that opening often in summer. Choose sliding doors if you want the biggest panes of glass, the clearest view when the doors are shut, and no folded stack to find space for. For most UK extensions, the doors spend more time closed than open, which is why sliders have become so popular.
At Inspired Glazing we fabricate and fit both, so we have no reason to push one over the other. This guide compares the bifold vs sliding doors question using the systems we install: Smart Visofold and Cortizo bifold doors, and Reynaers ConceptPatio 130 (CP 130) sliding doors. Every specification below comes from the manufacturer’s own page, linked in the text. Where a figure is not published, we say so.
Bifold vs sliding doors at a glance
| Feature | Bifold (Smart Visofold 1000 / Cortizo Bi-Fold) | Sliding (Reynaers CP 130) |
|---|---|---|
| Opening width | Almost the full width | Typically half (2 panels) or two-thirds (3 rails) |
| Maximum panel size | Visofold 1000: 1,200 mm wide x 2,500 mm high. Cortizo: 1,200 mm x 3,000 mm | 2,700 mm wide x 2,700 mm high |
| Maximum panel weight | Visofold: not published. Cortizo: 120 kg | 300 kg |
| Sightlines when closed | A frame every 1.2 m or less; Visofold typical sightline 122 mm | Few, wide panes; one meeting stile per pair |
| Thresholds | Low threshold option (Visofold) | Low and zero threshold options |
| Weather rating (air / water / wind) | Cortizo: 4 / 9A / A3. Visofold: not published | 4 / E750 / B5 |
| Thermal | Visofold: 1.4 W/m²K. Cortizo: Uw from 1.1 W/m²K | Uw = 1.4 W/m²K |
| Security | Cortizo: PAS 24:2012. Visofold: PAS 24 roller and top guide | Burglarproof variant available |
| Space needed | Room for the folded stack | None beyond the frame |
Sources: Reynaers CP 130, Smart Visofold 1000, Cortizo Bi-Fold System. Figures are manufacturer maximums or test results; your actual sizes depend on the survey.
How bifold and sliding doors work
Bifold doors are a row of hinged panels that fold against each other, concertina-style, and stack at one or both ends of the opening. Cortizo’s system can run from 1 to 14 sashes, folding up to 7 each side.
Sliding doors have large panels that glide past each other on tracks. Reynaers CP 130 comes in 2-rail, 3-rail and monorail layouts, as a standard slider or a lift-and-slide version for heavier panels. An open-corner option lets panels slide away at 90 degrees.
Sightlines and views
This is where sliding doors usually win. A slider uses a few very large panes, so when the doors are closed you see glass rather than frame.
Bifolds need a frame every time a panel folds. Smart Visofold 1000 panels are up to 1,200 mm wide with a typical sightline of 122 mm, according to Smart. So a 4.8 m opening needs at least four panels and has a vertical frame roughly every 1.2 m.
Practical tip: stand in your kitchen and look at the garden for a minute. If you mostly look out rather than walk out, sightlines matter more than opening width.
Panel sizes and opening width
Bifold doors: almost the full width
When fully folded, bifolds open close to the whole width. MyBuilder puts it at roughly 90–95% of the frame width. That makes them ideal for summer parties and an indoor–outdoor kitchen.
Panels are narrower but can be tall. Cortizo bifold sashes go up to 3,000 mm high and 120 kg each.
Sliding doors: bigger glass, partial opening
A two-panel slider opens about half the width; a three-rail slider opens about two-thirds. In return, each CP 130 vent can be up to 2,700 mm wide and 2,700 mm high, weighing up to 300 kg. On a pocket configuration, panels can disappear into the wall, though this needs planning at the build stage.
Thresholds and level access
Both types can give a near-flush route into the garden. Reynaers lists both a low threshold and a zero threshold for CP 130; the zero option suits continuous flooring from inside to out. Smart offers a low threshold option for Visofold 1000.
A flush threshold needs careful drainage design outside. Plan it with your builder before the floor and patio levels are set.
Weather performance
Reynaers rates CP 130 at air class 4, water E750 and wind B5. Cortizo rates its Bi-Fold System at air class 4, water 9A and wind A3. On the EN 12208 water tightness scale, E750 sits above 9A. Smart does not publish weather classes on the Visofold 1000 page, though it mentions magnetic latches to hold leaves open in gusty winds.
MyBuilder notes that a quality rebated bifold can seal very well. For exposed riverside or hilltop homes, ask your installer for the test results of the exact configuration you are buying, not just the system headline.
Security
Both types can be very secure when specified properly. Cortizo’s bifold holds a PAS 24:2012 certificate. Smart lists PAS 24 approval for the Visofold 1000 standard roller and top guide, plus a heavy-duty shoot bolt handle. Reynaers offers a Burglarproof variant of CP 130; ask us which certification applies to the configuration you choose. [CP 130 SECURITY CERTIFICATION AS SUPPLIED]
Bifolds lock along every leaf. Sliders usually lock at the meeting stile and frame, so hardware quality matters more than door type.
Cost: bifold vs sliding doors
Price depends on width, height, glass, colour and structural work. For a third-party benchmark, MyJobQuote’s September 2026 guide puts aluminium bifold doors at £3,150 to £7,200 supplied and fitted for three to five panels, assuming an existing opening.
Our own guide prices:
- Smart Visofold bifold, typical 3–4 m opening: quoted individually after a free survey
- Cortizo bifold, typical 3–4 m opening: quoted individually after a free survey
- Reynaers CP 130 slider, typical 3–4 m opening: quoted individually after a free survey
Large-format sliders can cost more per metre than bifolds because of the glass size and weight. Bifolds have more hinges, rollers and locks. Get both quoted for the same opening before deciding.
Which suits your extension layout?
| Your extension | Our usual recommendation |
|---|---|
| Opening under about 2.4 m | Two-panel slider |
| Wide opening, garden used often in summer | Bifold (Visofold or Cortizo) |
| Wide opening, view matters most | CP 130 slider, 2- or 3-rail |
| Corner of an extension | Bifold or CP 130 open-corner |
| Patio furniture or planters next to the door | Slider (no stack to clear) |
| Need a daily-use door for kids or pets | Bifold with a traffic door (we confirm availability for your configuration at survey) |
| Exposed site | Compare tested weather classes for the exact size |
| Very tall opening | Cortizo bifold (to 3,000 mm) or CP 130 (to 2,700 mm) |
MyBuilder also suggests a two-panel slider for openings under about 2.4 m, which matches what we see on surveys.
Our verdict
If you open the doors most days from May to September and love a full indoor–outdoor space, choose bifolds. If you want light, views and simplicity all year, choose sliders. Still unsure? See our aluminium bifold doors and Reynaers sliding doors pages, compare Smart Visofold vs Cortizo, or book a survey and we will quote both for your opening.
Related pages
- Aluminium bifold doors
- Reynaers aluminium sliding doors
- Windows and doors in Surrey
- Windows and doors in Kent
- Windows and doors in Sussex
Useful guides
- How much do aluminium windows cost in Kent and Surrey? (2026 price guide)
- Do you need planning permission to replace windows?
Frequently asked questions
Are bifold or sliding doors better for a small opening?
Sliding doors are usually better for small openings. Bifolds lose a frame every 1.2 m or less, and on a narrow opening that frame takes up a large share of the view. A two-panel slider suits openings under about 2.4 m.
Do sliding doors let in more light than bifold doors?
Yes, when closed, sliding doors usually let in more light. They use fewer, larger panes, so there is less frame in the opening. When fully open, bifolds give the wider gap.
Are bifold doors going out of fashion?
No, bifold doors remain a popular choice for UK extensions. Sliding doors have grown in popularity because many people keep their doors closed for most of the year and want bigger glass. The right choice depends on how you use the space.
Does Inspired Glazing fit Reynaers bifold doors?
No. Our bifold doors are Smart Visofold and Cortizo. From Reynaers, we fit ConceptPatio 130 sliding doors and SlimLine 68 windows.
How much space do bifold doors need when open?
Bifolds need space for the folded stack at one or both ends of the opening. MyBuilder suggests roughly 400 to 600 mm of clear wall or patio. Check that furniture, planters or steps will not block the stack.
Can sliding doors have a level threshold?
Yes, many sliding doors can have a level threshold. Reynaers offers both low and zero threshold options on ConceptPatio 130. A flush threshold needs good external drainage, so plan it before floor levels are set.