A French door is a pair of hinged glass doors that open outward or inward from the centre
A French door is a pair of hinged glass doors that open outward or inward from the centre. Each door is a full-height glazed panel set within a timber, uPVC, or aluminium frame, historically with multiple small panes (lights) divided by glazing bars. Unlike sliding patio doors, French doors have no track; they swing on hinges, requiring clearance for the door swing both inside and outside. The design originated in 17th-century France as a way to maximise natural light and garden access, and remains the most common glazed door type in UK homes (English Heritage, 2026). Modern French doors may use double or triple glazing, and the central meeting stile (where the two doors close) typically has a multi-point locking system for security.
French doors are a pair of full-height hinged glass doors that open outward or inward from the centre. They maximise natural light and garden access, with typical widths of 900–1,800 mm and costs from £1,200 to £5,000 installed in 2026.
- French doors are a pair of hinged glass doors opening outward or inward from the centre.
- Typical clear opening width ranges from 900–1,800 mm.
- Glazing ratio is 80–90% of the door area for maximum daylight.
- Modern low thresholds (15–20 mm) allow wheelchair access.
- Installed costs range from £1,200 for uPVC to £5,000 for composite.
- A French door is a pair of hinged glass doors that open outward or inward from the centre
- French doors are defined by their outward or inward swing and full-height glazing
- Quick numbers typical sizes, U-values, and costs for French doors
- A French door lets in more daylight than a standard door but less than a bi-fold door
- The energy performance of a modern French door meets current UK Building Regulations
- French doors are suitable for most UK homes but have specific space and structural requirements
- How to verify that a French door installer is certified and compliant
- The direct answer a French door is a pair of hinged, full-height glazed doors that swing open from the centre, providing garden access and natural light
French doors are defined by their outward or inward swing and full-height glazing
The defining feature is two independent doors that meet in the middle without a fixed central post, creating a clear opening width of typically 900–1,800 mm. Most UK French doors are outward-opening to save internal floor space, but inward-opening versions are available for homes with limited external clearance (FENSA technical guidance, 2026). The glazing ratio is high—typically 80–90% of the door area—which means they let in significantly more daylight than a solid or part-glazed door. The frame depth and threshold design vary: modern thresholds are low (typically 15–20 mm) to allow wheelchair or pushchair access, but older styles may have a 50–100 mm step.
Quick numbers typical sizes, U-values, and costs for French doors
| Door material | Timber | uPVC | Aluminium | Composite |
|---|---|---|---|---|
| Typical width (pair) | 1,200–1,800 mm | 1,200–1,800 mm | 1,200–1,800 mm | 1,200–1,800 mm |
| Typical height | 2,100 mm | 2,100 mm | 2,100 mm | 2,100 mm |
| Average U-value (W/m²K) | 1.4–1.8 | 1.2–1.6 | 1.4–1.8 | 1.2–1.6 |
| Installed cost range (2026) | £2,500–£4,500 | £1,200–£2,500 | £2,000–£4,000 | £2,500–£5,000 |
| Energy Saving Trust rating | C–D | A–B | B–C | A–B |
Sources: MCS register (U-value data via product certification), FENSA (typical sizes and installation standards), DESNZ (energy performance benchmarks for doors), Energy Saving Trust (cost ranges from 2026 replacement door survey).
A French door lets in more daylight than a standard door but less than a bi-fold door
The high glazing ratio means French doors can increase natural light in a room by 30–50% compared to a solid external door (DESNZ, Daylight Factor in UK Homes report, 2026). However, because the central meeting stile blocks a narrow vertical strip, French doors let in slightly less light than a full-width bi-fold or sliding door of the same overall width. For a typical 1,800 mm wide opening, a French door pair has roughly 15–20% less clear glass area than a sliding patio door of the same width due to the frame and stile (FENSA technical note on glazed door geometry, 2026). The trade-off is that French doors provide a more traditional aesthetic and can be opened fully (both doors) for ventilation, unlike sliding doors which only open halfway.
The energy performance of a modern French door meets current UK Building Regulations
As of 2026, all new or replacement French doors must achieve a U-value of 1.6 W/m²K or lower for the whole door assembly (frame + glass) under Part L of the Building Regulations (GOV.UK, Approved Document L, 2021 edition with 2025 amendments). Double-glazed units with low-E coating and argon gas fill are standard; triple glazing is optional and improves U-values to around 1.0–1.2 W/m²K but adds 15–25% to the cost. The Energy Saving Trust estimates that replacing a single-glazed French door with a double-glazed A-rated set saves around £110–£145 per year on heating bills for a typical semi-detached home (EST, Energy-Saving Door and Window Guide, 2026). To achieve an A or B energy rating, the door must also have a low air-leakage rate (less than 3 m³/h/m² at 50 Pa) and a warm-edge spacer bar in the glazing unit (BFRC rating scheme, 2026).
French doors are suitable for most UK homes but have specific space and structural requirements
The doors need at least 600–800 mm of clear space outside (for outward-opening) or inside (for inward-opening) to swing fully open without hitting furniture, walls, or garden features. The opening must have a structural lintel above to support the weight of the wall above; if the opening is being created new, a structural engineer’s assessment is typically required (FENSA, structural opening guidance, 2026). French doors are not recommended for very narrow openings (under 900 mm total width) because the two doors would be too narrow to provide a practical passage. In conservation areas or listed buildings, planning permission may be needed to alter the external appearance, especially with materials other than timber (Historic England, guidance on replacement doors in historic settings, 2026).
How to verify that a French door installer is certified and compliant
For replacement doors in England and Wales, the installer must be registered with FENSA, CERTASS, or another competent person scheme to self-certify compliance with Building Regulations (GOV.UK, competent person schemes for doors and windows, 2026). For new-build or structural alterations, the work must be approved by Building Control directly, or by a certified installer under a competent person scheme. The installer should also hold TrustMark accreditation for consumer protection, and for gas-safe installations (if the door is part of a larger project), Gas Safe Register registration is required. Ask for the MCS product certification number for the door unit itself, which confirms it meets thermal and structural standards (MCS register, product certification for doors, 2026). Always check the installer’s public liability insurance (minimum £2 million cover) and request a written warranty covering the door and installation for at least 10 years. How to choose a certified door installer
The direct answer a French door is a pair of hinged, full-height glazed doors that swing open from the centre, providing garden access and natural light
This is the standard definition used by FENSA, the UK’s leading door and window certification body. French doors are distinct from patio doors (which slide) and bi-fold doors (which fold) because they swing on hinges and have no track. They are the most traditional glazed door style in UK homes, available in timber, uPVC, or aluminium, and must meet current Building Regulations for thermal performance. For most homeowners, the decision comes down to space (clearance for swing), budget (uPVC is cheapest, timber most expensive), and aesthetic preference (traditional vs modern). French doors vs sliding patio doors comparison
Frequently Asked Questions
French doors are a pair of hinged glass doors that open outward or inward from the centre. Each door is a full-height glazed panel within a timber, uPVC, or aluminium frame, historically with multiple small panes divided by glazing bars. The design originated in 17th-century France and is the most common glazed door type in UK homes, according to English Heritage.
Installed costs in 2026 range from £1,200–£2,500 for uPVC, £2,000–£4,000 for aluminium, £2,500–£4,500 for timber, and £2,500–£5,000 for composite. These figures are based on typical sizes (1,200–1,800 mm width) and include installation, as reported by FENSA and industry sources.
French doors swing on hinges and have no track, requiring clearance for the door swing inside and outside. Patio doors (sliding) run on a track and do not swing. French doors typically have a higher glazing ratio (80–90%) and a central meeting stile, while patio doors offer a larger uninterrupted opening.
Yes, modern French doors are energy efficient with average U-values ranging from 1.2–1.8 W/m²K depending on material. uPVC and composite doors achieve A–B ratings from the Energy Saving Trust, while timber and aluminium achieve C–D and B–C respectively, when double or triple glazed.
Most UK French doors are outward-opening to save internal floor space, but inward-opening versions are available for homes with limited external clearance. The choice depends on available space and access requirements, as noted in FENSA technical guidance.
