A simple guide to sliding patio doors. Learn interlocks, lift-and-slide systems, U-values, and top brands with expert advice from GFD Homes.
What You’ll Learn:
- How Sliding Patio Doors Work
- The Meaning Behind Key Technical Terms
- What to Think About Before Ordering
- The Essentials You Need to Buy With Confidence
(Estimated Reading Time: 5-6 Minutes)
Introduction: Sliding Doors Are Simple, Right?
Sliding patio doors seem simple — big glass panels that glide open. But once you start researching, you quickly run into terms like interlocks, lift-and-slide, thermal breaks, U-values, and track configurations. Suddenly, choosing a door becomes a technical puzzle rather than a straightforward upgrade.
This guide from GFD Homes breaks down the jargon into plain English so you can confidently choose sliding patio doors that suit your home, your budget, and your lifestyle.
1. What Are Sliding Patio Doors, Really?
A sliding patio door consists of two or more glass panels that glide horizontally along a track.
Unlike bifold doors, which fold away, sliding doors move parallel — allowing for huge panes of uninterrupted glass and seamless transitions between indoors and outdoors.
They’re popular in modern extensions, open-plan kitchens, and garden rooms — anywhere natural light and minimal sightlines matter.
2. The Key Terms Explained
a. Interlock
The interlock is the vertical bar where two sliding panels meet.
It’s the only visible join when the doors are closed.
Why it matters:
Slimmer interlocks mean more glass and better views. Premium systems like Cortizo can have interlocks as slim as 20–30 mm.
Consider:
Slimmer = sleeker, but heavier glass means thicker interlocks for strength — it’s about balance.
b. Lift-and-Slide Mechanism
This refers to how the doors operate.
When you turn the handle, the panel gently lifts off the seal before sliding, reducing friction.
Why it matters:
- Easier to move large panes (even 3 m wide).
- Better weather sealing when closed.
- Smoother and quieter operation.
Example: Premium systems like Cortizo 4700 and Smart Visoglide use lift-and-slide tracks.
c. Track Options (Double / Triple)
Sliding doors run along tracks — rails that guide the panels.
- Double Track: Two panels can slide past each other.
- Triple Track: Allows three or more panels with multiple opening combinations.
Why it matters:
Triple tracks offer more flexibility — ideal for very wide openings.
d. Thermal Break
Inside every good aluminium frame is a thermal break — a section of non-metallic material that stops heat from escaping.
Why it matters:
It’s the difference between a cold, condensation-prone door and a warm, efficient one.
Expect U-values as low as 1.3–1.5 W/m²K on modern systems.
e. U-Value
Measures how well the door insulates.
Lower = better.
Typical range: 1.3–1.6 W/m²K.
Why it matters:
A low U-value keeps your home comfortable and bills lower.
f. Glazing Specification
Sliding doors use toughened double glazing as standard, but you can upgrade.
Options:
- Laminated Glass: Improves security and sound insulation.
- Solar-Control Glass: Reduces glare and overheating.
- Triple Glazing: Further improves energy efficiency.
Why it matters:
The right glazing improves comfort year-round — especially in south-facing rooms.
g. Cill & Drainage
A cill is the base section that channels water away from the door.
Drainage slots allow rainwater to escape, preventing pooling.
Why it matters:
Proper drainage protects your flooring and threshold.
Always ensure your installer uses the manufacturer’s recommended cill system.
h. Handle Type / Locking System
Handles vary from recessed (flush) to lever types.
Locks typically use multi-point systems for added strength.
Why it matters:
The right hardware affects security and usability — especially for heavy panels.
i. Frame Depth
Frame depth determines how the system fits into your wall opening.
Shallower frames look sleeker but may offer less insulation.
Deeper frames can hold triple glazing for top-tier performance.
3. The Leading Systems Explained
Smart Visoglide Sliding Doors
- From £1,967 inc VAT
- Trusted UK system, perfect for extensions and open-plan living.
- Lift-and-slide operation.
- U-values around 1.4 W/m²K.
- PAS 24 security rated.
A solid choice for performance, aesthetics, and reliability.
Cortizo 4700 Slimline Sliding Doors
- From £3,250 inc VAT
- Ultra-slim interlocks and modern European design.
- Smooth-glide rollers and concealed frames.
- Outstanding energy and acoustic performance.
If you’re looking for luxury architectural styling, this is it.
Korniche Sliding Systems
- From £1,950 inc VAT
- Perfect balance of design, thermal efficiency, and value.
- Matching finishes with Korniche bifolds and roof lanterns.
An ideal choice for those who want modern minimalism without the luxury markup.
4. Commonly Confused Terms
| Term | What It Means | Why It Matters |
|---|---|---|
| Interlock | The vertical join between panels | Impacts how much glass you see |
| Track | The base rail the panels slide on | Determines opening options |
| Lift-and-Slide | A mechanism lifting panels off seals | Makes movement smoother |
| Thermal Break | Insulation layer in aluminium | Reduces heat loss |
| U-Value | Insulation rating | Lower = warmer home |
| Cill | Drip ledge at base | Prevents water ingress |
| Laminated Glass | Two sheets bonded with film | Adds strength and soundproofing |
5. What to Consider Before Buying
- Opening Size & Layout:
- Measure your space accurately (to the millimetre).
- Consider furniture placement and walkways.
- Exposure:
- Choose robust seals and drainage for exposed areas.
- Security:
- Look for PAS 24 rating and laminated glass upgrades.
- Aesthetic:
- Slimline frames for modern looks.
- Colour-match to your windows and bifolds.
- Budget vs Performance:
- Higher-end models may cost more, but deliver better comfort and durability.
6. Buying Direct — Keep the Control
Just like with other products, ordering in your name keeps your warranty and support secure.
If your builder orders, the warranty belongs to them. If something goes wrong, you’ll have to go through them to get a repair.
Buying direct from GFD Homes ensures:
- Warranty in your name.
- Access to our expert aftercare team.
- UK-wide delivery and full documentation.
7. Smart Buying, Simple Pricing
You can get an instant, 100% accurate price for your sliding doors directly online — no pushy sales visits, no guesswork.
Try it now:
Every quote is calculated to the millimetre, including your exact configuration, colour, and glass options.
8. In Summary
By now, you know:
- What interlocks and lift-and-slide systems actually do.
- Why thermal breaks and U-values impact your comfort.
- How tracks, drainage, and glazing choices shape performance.
- And most importantly — how to buy with confidence, not confusion.
Sliding doors are simple again.
And with GFD Homes, you can design, price, and order online — backed by experts who care about getting it right.
🛒 Browse the full collection at www.gfdhomes.co.uk
📞 Or call 01642 309576 for expert guidance and a no-pressure quote.
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FAQ’s
1. Are sliding patio doors better than bifold doors?
Sliding patio doors offer larger uninterrupted glass panels, while bifolds open the full wall. As explained in Sliding Patio Doors : Sliding Patio Doors Demystified: Slim Lines, Big Questions by GFD Homes, sliders are ideal when maximising views is the priority.
2. What is an interlock and why does it matter?
The interlock is the vertical join between panels. Slimmer interlocks mean better views. GFD Homes explains in the guide that premium systems like Cortizo can reach as low as 20–30 mm.
3. Are lift-and-slide doors worth it?
Yes — they lift the panel before sliding, making large panes easier to move and improving sealing when closed. GFD Homes highlights this as a key upgrade in modern sliding patio doors.
4. What’s the best glazing for sliding patio doors?
Double glazing is standard, but laminated, solar-control, and triple glazing can improve security and comfort. GFD Homes recommends choosing based on orientation and room use.
5. Do sliding patio doors lose heat easily?
Not modern ones. With proper thermal breaks and good glass, sliding patio doors achieve U-values around 1.3–1.6 W/m²K. GFD Homes covers how these ratings impact real-life warmth.
