French Doors Supply & Fit London & Surrey

Double French Door Supply and Installation

Double French doors provide a classic symmetrical opening that connects indoor living spaces directly to gardens, patios, and balconies. Utilizing a precision master-and-slave leaf mechanism with a floating central mullion, both doors swing fully clear to create a 100% unobstructed walk-through aperture with zero central pillar dividing the view.

Window Fitters Ltd provides precision French door installation across London and Surrey. We fit high-performance multi-chambered uPVC, thermally broken aluminium, steel-look Heritage profiles, and engineered timber French doorsets. Whether you require a full supply and fit package or a dedicated labour-only glazier team to install client-procured doorsets, our directly employed installers ensure precision 3D hinge calibration, diagonal toe-and-heel glass packing, and complete compliance with UK Building Regulations Approved Documents L, K, Q, and F.

French Door Profile Materials & Architectural Comparison

Choosing the right profile material depends on opening width, architectural style, and thermal requirements:

Master and Slave Floating Mullion Mechanics

Traditional double doors often featured a fixed central post that divided the doorway permanently. Modern French doors eliminate this obstruction through an engineered floating mullion mechanism:

• Primary Master Leaf: Functions as the daily entrance door. Fitted with an ergonomic lever/lever handle, multi-point locking hooks, roller cams, and an anti-snap cylinder. This leaf opens first and latches securely into the floating mullion on the secondary leaf.
• Secondary Slave Leaf: Carries the aluminium or uPVC floating mullion rebated down its leading edge. It is locked top and bottom into the outer frame using concealed finger-operated shootbolts or an integrated internal lever mechanism.
• Full Clear Walkway: Opening the slave leaf swings the entire central mullion clear of the doorway, providing a completely unobstructed opening for moving furniture, entertaining, or garden ventilation.
• Interlocking Rebates: Dual EPDM rubber compression gaskets bridge the meeting stiles, creating a weather-tight thermal barrier against driving wind and rain.

Outward vs Inward Opening Trade Considerations

French doors can be configured to open outward into the garden or inward into the room:

• Outward Opening (UK Standard): The most popular configuration across London and Surrey. Leaves fold flat against external walls, preserving valuable indoor living space for dining tables, sofas, and curtains. Prevents rain water on wet door faces from dripping onto internal carpets when opened.
• Inward Opening: Specified for Juliet balconies, upper-floor master bedrooms, or properties where external patios have limited clearance or raised step-downs.
• 90-Degree Top Friction Stays: Outward-opening doors are fitted with concealed top friction restrictors that control the swing angle, preventing high winds from slamming leaves into brickwork.
• External Door Hooks: Magnetic door catches or brass cabin hooks can be fitted externally to anchor leaves firmly in the fully open position during summer months.

Diagonal Toe-and-Heel Glazing and 3D Hinge Fine-Tuning

Because double French doors have two wide, heavy sashes that meet in the middle without a centre post, precision glass packing is critical. A standard 28 mm double-glazed unit weighs between 20 kg and 35 kg per leaf. Without proper support, the unhung lock stiles will drop over time, causing the doors to drag along the threshold and jam:

• The Toe-and-Heel Principle: Glass is inherently rigid. Load-bearing plastic bridge packers are inserted diagonally across the glass perimeter, placing packers at the bottom hinge corner (heel) and the top opposite locking corner (toe). This turns the sealed unit into an internal diagonal brace that transfers the entire leaf weight back into the hinge jamb.
• 3D Flag Hinge Calibration: High-performance French doors feature heavy-duty flag hinges with three-way Allen key adjustment: lateral horizontal adjustment (+/- 3 mm) to set an even 3 mm gap between meeting stiles, vertical height adjustment (+/- 4 mm) to eliminate threshold dragging, and gasket compression adjustment (+/- 1.5 mm) for optimal draught exclusion.
• Perimeter Plumb Setting: Outer frames are fixed into the masonry using direct concrete screws and high-density composite shims, ensuring the jambs remain perfectly plumb within 1 mm over a 2,100 mm height.

Threshold Engineering: Weather Rebates vs Part M Low Access

Threshold selection determines weather performance and step-free accessibility:

• Standard Rebated Outer Frame (65 mm to 70 mm): Features an integral full-frame upstand that offers maximum weather tightness against heavy driving rain. Ideal for exposed rear elevations, upper-floor balconies, and south-facing garden aspects.
• Thermally Broken 15 mm Low Aluminium Threshold: Meets Approved Document M requirements for wheelchair and pushchair accessibility. Sits almost flush with internal finished flooring, fitted with internal thermal breaks and concealed drainage weep channels.
• Sub-Cill Detailing: Installed on 150 mm or 180 mm projecting external sub-cills with end-caps and continuous DPC bedding, ensuring rainwater clears the brickwork below.

French Door Installation Costs & Market Estimates

Below are transparent market price benchmarks for complete supply and fit packages compared with labour-only glazier installation rates across London and Surrey:

UK Building Regulations & Security Standards for French Doors

Every replacement French doorset must satisfy strict statutory standards under UK Building Regulations:

• Approved Document L (Conservation of Fuel & Power): Replacement external doors must achieve a minimum whole-doorset Ud value of 1.4 W/m²K or a Door Energy Rating (DER) of Band C. We glaze with 28 mm soft-coat Low-E glass, warm-edge composite spacer bars, and 90% argon gas to achieve Ud ratings of 1.2 to 1.4 W/m²K.
• Approved Document K (Protection from Collision & Impact): Under BS EN 12600 Class 1, toughened or laminated safety glass is legally mandatory across both full-height door leaves and any adjacent sidelight within 300 mm of the door edge up to 1,500 mm height.
• Approved Document Q & PAS 24 (Security): Ground-floor and accessible French doors must resist physical attack. Fitted with anti-lift security shootbolts, steel hook deadbolts, and TS007 3-star anti-snap cylinders to deter forced entry.
• Approved Document F (Ventilation): Where replacement doors enclose a habitable room without dedicated continuous mechanical extract, overhead frame trickle ventilators providing a minimum equivalent area of 8,000 mm² are integrated into the frame head.

Explore our related door and glazing guides: review our complete doors directory, follow our 6-stage door installation workflow, consult skilled door fitters, compare French doors with wide-aperture bifold doors and space-saving sliding patio doors, learn how to adjust hinges in our door hinge guide, check overall pricing in our installation cost guide, and discover our dedicated labour-only installation teams.

Heritage and Crittall-Style Door Fitting

The demand for heritage aluminium French doors in London is exceptionally high, particularly for properties looking to replicate classic Art Deco or industrial aesthetics. Window Fitters Ltd installs both genuine steel doors (such as Crittall and Otif, achieving sightlines as slim as 20 mm) and premium thermally broken aluminium heritage alternatives. Leading aluminium systems we fit include Aluco Elite, Origin OB-36 Soho, and Smart Alitherm Heritage 47. These systems feature surface-mounted astragal glazing bars and deep bottom rails to faithfully recreate traditional sightlines.

The Floating Lock Innovation

One of the primary challenges with standard aluminium French doors is the bulky central meeting stile required to house the locking mechanism. Premium systems like Aluco overcome this using a floating lock design. By relocating the main locking gearbox into an external lock body, the main aluminium extrusion profiles can be substantially reduced. This innovation provides a significantly slimmer meeting stile, creating ultra-slim exterior French doors that maximise visible glass area.

Conservation Area Guidance

Installing new French doors in conservation areas often requires careful planning. If your property is subject to an Article 4 direction, permitted development rights are restricted, and you must obtain planning permission before making external changes. In these zones, local authorities typically require a like-for-like aesthetic replacement. Our installation teams regularly work alongside homeowners and architects during the planning pre-application stage, fitting approved heritage profiles that satisfy strict conservation office requirements.

For local expertise, we provide dedicated services including Richmond door installation and Wimbledon door installation.

Frequently Asked Questions About Double French Doors

Find key trade answers regarding double French door fitting tolerances, master-slave lock mechanisms, Part M low thresholds, and PAS 24 security standards.