French doors — a pair of outward- or inward-opening glazed panels on a central pair of hinges — are the most straightforward way to connect a ground-floor room to a garden. They are simpler to manufacture, install, and maintain than bifold or sliding alternatives, and they work well for openings up to about 1,800 mm wide. Beyond that, a bifold or sliding door gives you a more useful clear opening.
What Do French Doors Cost?
The cost depends mainly on material and specification. uPVC remains the most affordable option; aluminium has grown to dominate the mid-to-upper market; timber suits heritage and conservation settings.
| Material | Supply-Only | Supply & Fit |
|---|---|---|
| uPVC, double-glazed | £450 – £1,100 | £800 – £1,800 |
| uPVC, triple-glazed | £600 – £1,400 | £1,000 – £2,200 |
| Aluminium, thermally broken, double-glazed | £900 – £2,200 | £1,500 – £3,500 |
| Aluminium, thermally broken, triple-glazed | £1,200 – £2,800 | £1,900 – £4,200 |
| Hardwood timber, double-glazed | £1,200 – £2,800 | £1,800 – £4,500 |
| Softwood timber, painted, double-glazed | £800 – £1,800 | £1,300 – £3,200 |
| Steel heritage profile | £2,500 – £5,000 | £3,500 – £7,000+ |
Prices per pair of doors, standard width 1,200–1,800 mm, standard height 2,100 mm. Sidelights, transoms, or non-standard heights increase cost.
Standard Sizes
French doors are manufactured in standard widths and heights, with bespoke sizes available at higher cost.
| Dimension | Common Sizes |
|---|---|
| Total width (pair) | 1,200 mm · 1,500 mm · 1,800 mm |
| Leaf width (single panel) | 600 mm · 750 mm · 900 mm |
| Height | 2,050 mm · 2,100 mm · 2,250 mm · 2,400 mm |
| Frame depth | 70–110 mm depending on material |
Most replacement openings in a brick rear wall are 1,200 mm or 1,500 mm wide. An 1,800 mm opening is increasingly common in newer builds and larger kitchen extensions. Beyond 1,800 mm, the pair of panels becomes very wide per leaf and the door becomes unwieldy unless it is outward-opening with adequate patio space.
Clear opening width is approximately 80–90% of the total aperture once frame members are accounted for — a 1,500 mm total width typically gives a 1,250–1,350 mm clear passage.
Material Options Compared
| Feature | uPVC | Aluminium | Timber |
|---|---|---|---|
| Whole-unit U-value | 1.2 – 1.8 W/m²K | 0.9 – 1.5 W/m²K | 1.3 – 1.8 W/m²K |
| Frame sightline width | 90–120 mm | 55–80 mm | 80–110 mm |
| Maintenance | Very low | Very low | Medium–high |
| Lifespan (typical) | 20–30 years | 30–45 years | 40–80 years (with upkeep) |
| Colour options | White standard, limited range | Any RAL colour | Paint or stain any colour |
| Conservation suitability | Poor | Moderate | Best |
| Cost relative to others | Lowest | Mid | Mid to highest |
uPVC is the default choice for budget-conscious buyers. The frames are bulkier than aluminium, and the colour options are limited, but they are weathertight and thermally adequate for most applications.
Aluminium (thermally broken) has slim sightlines and a premium appearance. It dominates the market for modern extensions and is available in virtually any RAL colour. Thermal performance matches or exceeds uPVC when properly specified.
Timber is the material of choice for conservation areas, listed buildings, and period properties where character matters. Hardwood (oak, meranti) is more durable than softwood but significantly more expensive. All external timber requires re-painting or re-staining every 5–8 years.
Steel heritage profile is a specialist product — very slim sightlines (20–30 mm), the aesthetic of 1920s–1940s Crittall-style glazing, and genuine longevity. Cost is high and installation requires a specialist contractor. Worth considering in architecturally important renovation projects.
Building Regulations
External French doors are subject to the same Approved Document L requirements as any other external door glazing:
- Whole-unit U-value ≤1.4 W/m²K for replacement doors in existing dwellings (England and Wales, 2026)
- Safety glazing required for panes within 1,500 mm of floor level and within 300 mm of a door edge — toughened or laminated glass to BS EN 12600 Class 1C or 2C
- Fire egress: where French doors serve as the main escape route from a room, the clear opening width must be sufficient (750 mm minimum is the general guidance)
- New openings in loadbearing walls require a structural engineer’s lintel specification and, in most cases, a Building Regulations application. A competent builder will know when this applies.
Opening Direction: Inward or Outward?
French doors are most commonly outward-opening in the UK for two practical reasons: they do not encroach on the interior floor area when open, and they create a more natural transition to a patio or decking. However:
- Outward-opening doors require clear patio space immediately outside — at least 900 mm in front of each leaf
- Inward-opening doors are more thermally efficient (the frame compression on the weather seals increases with wind pressure) and do not require clear external space, but they need interior clearance
Most manufacturers offer both configurations at no cost difference. Decide based on your specific layout.
French Doors vs Bifolds vs Sliding
| Factor | French Doors | Bifold (4-panel) | Sliding (2-panel) |
|---|---|---|---|
| Typical opening width | Up to 1,800 mm | Up to 3,600 mm | Up to 3,000 mm |
| Clear opening % | 80–90% | 80–85% | 45–55% |
| Typical cost (supply & fit) | £1,500 – £3,500 | £4,500 – £8,000 | £2,500 – £5,000 |
| Complexity | Low | Medium–high | Low–medium |
| Thermal performance | Good | Moderate | Very good |
| Maintenance burden | Low–medium | Medium | Low |
French doors are the right choice when the opening is under 1,800 mm and you want simplicity, reliability, and value. Bifolds suit wider openings where a fully clear span matters aesthetically. Sliding doors suit openings of any width where thermal performance and minimal stack depth are priorities.
Installation: What to Expect
A like-for-like replacement of French doors into an existing opening takes a skilled joiner one day, occasionally two. The process involves:
- Removing the existing door and frame
- Preparing the reveal and treating any rot or damp
- Fitting and securing the new frame (typically with expanding foam and frame fixings into the masonry)
- Hanging the door leaves and adjusting hinges and locks
- Sealing internally and externally with low-modulus silicone
If a new opening is being created, add structural works: building a temporary prop, cutting the opening, installing the lintel, and making good the masonry. This adds £500–£1,500 to the cost depending on wall construction and lintel specification.
FENSA- or Certass-registered installers will self-certify compliance and provide you with a certificate, which you will need when selling the property.
