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Bifold vs. Sliding Doors: The Ultimate Decision Guide (2025)
Bifold vs. Sliding Doors: The Ultimate Decision Guide (2025)
📌 Key Takeaways
- The View: Sliding doors have much thinner frames (more glass) when closed.
- The Opening: Bifold doors open up 90% of the wall; Sliders only open 50% – 66%.
- The Golden Rule: If your opening is under 3 metres, choose Bifolds. If over 4 metres, Sliders often look better.
- Convenience: Only Bifolds offer a “Traffic Door” (a normal back door) for everyday use.
It is the biggest debate in modern home renovation. You want to connect your kitchen or living room to the garden, but which system is best: the concertina folding action of a Bi-fold, or the sleek, gliding motion of a Sliding Door?
At KJM Group, we install hundreds of both every year across Hampshire. We know that neither is “better”—but one will be better for you.
Table of Contents
1. Comparison at a Glance
Before we dive into the technical details, here is how the two systems stack up on the features that matter most to homeowners.
| Feature | Bi-Folding Doors | Sliding Patio Doors |
|---|---|---|
| Opening Capacity | 90% Open. The doors stack neatly to the side, leaving a clear hole. | 50% – 66% Open. The doors must slide behind each other, always leaving glass in the way. |
| View When Closed | More visible frame. Vertical lines every ~1 metre. | Panoramic View. Huge panes of glass with minimal vertical lines. |
| Daily Access | Excellent. Can have a single “Traffic Door” for quick access. | Good. You can slide it open slightly, but there is no hinged door. |
| Sightlines (Frame Width) | Approx 132mm (where two doors meet). | As slim as 20mm – 35mm (interlock). |
2. The Case for Bifold Doors (The “Open” Wall)
Bifold doors are designed for people who want to erase the boundary between inside and outside.
Their superpower is the ability to fold completely out of the way. If you love hosting summer BBQs where guests drift between the kitchen and the patio, nothing beats a bifold.
💡 The “Traffic Door” Advantage
One major advantage of Bifolds (specifically those with an odd number of panels, e.g., 3, 5) is the Traffic Door. This acts like a normal back door. You can pop out to hang the washing or let the dog out without unlocking the entire folding mechanism. Sliders generally do not offer this.
3. The Case for Sliding Doors (The “Glass Wall”)
Sliding doors have made a massive comeback in recent years. Why? Because of Architecture.
Modern sliding doors, like our Smart Visoglide range, can support huge panes of glass (up to 2.5m or even 3m wide). This creates a “wall of glass” effect.
If you have a beautiful view of the Hampshire countryside, a sliding door frames it like a picture. A bifold door, by comparison, would break that view up with several vertical frames.
4. The “Sightline” Difference
This is the technical detail that usually sways the decision. The “sightline” is the amount of frame you see where two doors meet.
- Bifold Sightline: Typically around 132mm. Because two frames have to fold against each other, there is a chunk of aluminium/uPVC visible every metre or so.
- Slider Sightline: Modern aluminium sliders have an “interlock” (where the doors overlap) as slim as 20mm to 35mm.
KJM Recommendation: If your door is closed for 80% of the year (which, let’s be honest, in the UK it is), a Sliding Door gives you a better view. If you live for those 10 weekends of perfect summer weather, the Bifold wins.
5. Which Costs More?
This is a common question, but the answer is surprising: They are often very similar in price. However triple track sliding doors, or ones with much wider glass panes can make them much more.
Smaller sliding doors require less complex gearing (hinges/rollers) than bifolds, the glass units are much larger and heavier, which balances the cost. The price also depends more on the material (Aluminium vs. uPVC) and the specification (Triple Glazing, Integral Blinds) than the opening style.
Frequently Asked Questions
Technically, Sliding Doors often have a slight edge. This is because they have fewer frame joints and a higher ratio of glass-to-frame. Glass (especially high-spec Low-E units) is an incredible insulator. However, modern Bifolds with thermal breaks easily meet current Part L building regulations.
Yes, on both systems, but with a warning. A truly “flush” threshold has no weather rating (it will leak in driving rain). We always recommend a Weathered Threshold which has a small upstand (approx 15-20mm) to seal against the wind. We can often sink the frame into your floor to minimize the step-over height. Read our full guide on thresholds here.
This is where Sliders win. A single sliding sash can be up to 2.5m or 3m wide. A bifold sash is generally limited to 1.2m wide. If you have a 6-metre opening, you would need 5 or 6 bifold panels (lots of frame), but only 2 or 3 sliding panels (lots of glass).
Extremely. Both our Visofold (Bifold) and Visoglide (Slider) systems are PAS 24 certified and feature multi-point locking mechanisms. For peace of mind, look for the Secured by Design accreditation, a police initiative to improve home security.
Final Verdict: The KJM "Golden Rule"
If you are still stuck, use our simple rule of thumb regarding your aperture size:
- Small Opening (Under 3m): Choose Bifolds. A slider in a small hole restricts the opening too much (you only get 1.5m of walk-through space). A bifold opens it all up.
- Large Opening (Over 4m): Choose Sliders. A bifold would require too many vertical frames, cluttering your view. A slider looks majestic at this scale.
Visit our Andover Showroom to slide and fold them yourself. We have both systems on display so you can feel the difference.
📚 Related Reading
- Deep Dive: Technical Guide to Bifold Thresholds & Traffic Doors
- Material Choice: Why Aluminium is Best for Bifolds
- Keep it Cool: Solar Control Glass Explained
Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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