Patio Doors for Extensions: Bi-Fold vs Sliding vs French Doors

The rear door specification in a kitchen extension is one of the most visible design decisions — and one that significantly affects how the finished space feels. The three main options are bi-fold doors, sliding doors, and French (hinged) doors. Each has genuine advantages and limitations.

Bi-Fold Doors

Bi-fold doors open by folding in an accordion pattern — the panels fold and stack to one or both sides of the opening. The result is an opening that can be fully clear from edge to edge, merging the interior with the garden.

Advantages:

• Widest possible clear opening when fully open — ideal for indoor/outdoor entertaining
• Full clear aperture creates a dramatic visual connection to the garden
• Available in slim-profile aluminium systems that maximise glass area

Disadvantages:

• The track on the floor threshold is a trip hazard and a dirt trap
• When partially open, one or more panels swing into the room, taking up floor space
• More moving parts than sliding or French doors — more maintenance points
• Thermal performance of older systems was variable; modern thermally broken aluminium systems are good

Best for: Extensions designed for entertaining and indoor/outdoor living, where the fully open configuration will be used frequently.

Typical cost (3-pane, 2400mm wide, aluminium): £3,000–£8,000 supply only

Sliding Doors

Sliding (or sliding patio) doors move horizontally on a track. In a typical two-panel arrangement, one panel slides behind the other. In a three-panel arrangement, two panels can slide to one end.

Advantages:

• No floor track trip hazard in modern lift-and-slide systems (the door lifts slightly to slide)
• Smooth, clean operation
• No floor space consumed when open
• Better thermal performance than many bi-fold systems
• Slimmer sightlines available in premium systems

Disadvantages:

• Maximum open aperture is 50% of the total opening width (one panel behind the other)
• Limited opening width compared to bi-folds

Best for: Extensions where a large glazed rear elevation is desired but the fully open bi-fold configuration is less important; where a clean, modern aesthetic is preferred.

Typical cost (2-panel, 2400mm wide, aluminium lift-and-slide): £3,500–£9,000 supply only

French Doors (Hinged Patio Doors)

French doors are two hinged panels that open inward or outward from a central meeting point. Often paired with fixed side lights to increase the glazed area.

Advantages:

• Lowest cost of the three options
• Simple, proven, reliable hardware
• Wide range of styles — timber, aluminium, uPVC
• Period-appropriate for Victorian and Edwardian properties

Disadvantages:

• Hinged panels swing into the room (inward) or garden (outward), requiring clear space
• Smaller clear opening than bi-folds or large sliding doors
• Less dramatic visual connection to the garden

Best for: Budget-conscious projects, period properties where bi-folds would look out of character, or where the open aperture is not the primary priority.

Typical cost (2-panel plus side lights, aluminium): £2,000–£5,000 supply only

RCB Design & Build

RCB Design & Build advises clients on rear door specification as part of extension design — coordinating the structural opening size, glazing specification, and thermal performance requirements.