French Doors Buying Guide: How to Choose the Right Set

French doors are a practical way to add natural light and create a wide opening between a room and the garden, patio or terrace. The familiar pair of glazed leaves can suit both traditional and modern homes, but choosing the right set involves more than picking a colour. Overall frame size, glazing, master-leaf handing, threshold details and installation all need to work with the opening.

This complete UK French doors buying guide explains the main choices before you order. JJ Building Materials stocks French doors from Crystal in white and grey external finishes, with double- and triple-glazed options across multiple sizes. Always use the individual product page as the final source for current dimensions and specification.

What Are French Doors?

French doors use two hinged leaves that meet in the centre. One leaf is normally the master leaf used for everyday opening and locking, while the second leaf can be released when a wider opening is required. This gives a different experience from sliding patio doors and bi fold doors.

The symmetrical appearance works particularly well where you want a clear visual centre to the opening. Large glazed areas also allow more daylight into kitchens, dining rooms and living spaces.

uPVC French Doors

Our current range focuses on uPVC French doors. uPVC systems are supplied as complete framed units rather than bare door leaves, making the overall frame dimensions especially important. They are designed as coordinated systems with glazing, seals, locks, hinges and cill details.

Examples include the Crystal UPVC White French Door Clear Double Glazing Left Hand Master and grey/white variants with the same general door format. Compare the exact size variant, glazing and colour combination before ordering.

French Door Sizes

There is no single standard French door size for every UK property. Complete systems are offered in a range of overall frame widths and heights. Our Crystal products include multiple widths, so it is important to match the actual structural opening rather than relying on a nominal “4ft” or “5ft” description.

Use our French door sizes UK guide to understand frame dimensions, common opening widths and why complete doorset measurements differ from individual leaf sizes.

How to Measure for French Doors

Measure the structural opening at the top, middle and bottom for width and at the left, centre and right for height. Check diagonals and level, then compare the smallest reliable figures with the frame dimensions and fitting tolerance specified by the manufacturer.

Finished floor levels matter because French-door thresholds sit at the junction between internal flooring and external paving. Our how to measure for French doors guide covers the full survey sequence.

Double Glazing or Triple Glazing?

Our Crystal French-door range includes both double- and triple-glazed product variants. Rather than assuming one glazing type is automatically best for every project, compare the complete product specification, price and any declared thermal information. Frame design, seals and installation all contribute to whole-door performance.

For regulated work, use the values required by the project and current Building Regulations guidance. The number of panes alone is not enough to determine whether a product meets a specific target.

Clear Glazing and Privacy

French doors are usually chosen partly for light and views, so clear glazing is common. Consider the outlook from inside and the level of privacy the opening needs. A garden-facing rear elevation may suit clear glass, while a more exposed or overlooked location could need a different solution.

Check the exact product because glass type is not always a selectable option after purchase. Do not assume that a similar-looking door in another colour has identical glazing.

White or Grey French Doors

White uPVC gives a classic neutral finish that coordinates easily with many existing windows and fascias. Grey external finishes suit contemporary extensions and properties with anthracite-style windows or roofline products. Some products combine a grey exterior with a white interior, which can keep internal rooms brighter and easier to coordinate.

The Crystal UPVC French Door Grey 7016 External / White Internal is an example of this dual-colour approach. Read the full product title carefully so you know the finish on both sides.

What Does Left-Hand Master Mean?

On a pair of French doors, the master leaf is the primary leaf used for normal entry and locking. A left-hand master configuration identifies which leaf performs that role according to the manufacturer’s viewing convention. The exact viewpoint matters, so use the product diagram or supplier definition before ordering.

Think about the room layout and the route to the garden. The master leaf should open into a practical clear area without conflicting with furniture, kitchen units, radiators or external obstructions.

Do French Doors Open In or Out?

Opening direction depends on the product design. Check the exact system before purchase. Outward-opening leaves keep the room clear but need adequate patio or garden space; inward-opening leaves use internal floor area and may interfere with curtains or furniture.

Do not assume you can reverse a factory-made doorset on site. Handing, drainage and locking details are designed around a specific configuration.

Thresholds and Cills

Many complete French-door systems include a cill of a stated size. The cill helps project water away from the building and forms part of the bottom installation detail. Check whether it is included and whether its size affects the overall frame height or projection.

Plan external paving levels so drainage is not blocked. If you want a low transition between inside and outside, coordinate the threshold with the building design rather than raising paving against a standard cill after installation.

Security and Locking

French doors use coordinated locking and shoot-bolt or slave-leaf hardware depending on the system. Check the exact locking specification and how the secondary leaf is secured. The frame must also be fixed correctly into the building for the system to perform as intended.

A good doorset can be compromised by poor installation, so security should be considered as the combination of product and fitting rather than a hardware feature in isolation.

Thermal Performance

Large glazed doors can have a significant effect on a room’s heat loss, particularly in extensions. Compare whole-product thermal data where it is provided. If the project requires a specific U-value or other performance target, verify the exact variant rather than transferring a figure from another size or glazing option.

Professional installation and correct perimeter sealing are essential because gaps around the frame can undermine the benefits of a well-specified doorset.

French Doors vs Bi Fold Doors

French doors use two hinged leaves and create a classic central opening. Bi fold doors use multiple folding panels and can open a much wider proportion of the wall. French doors usually suit smaller or more traditional openings, while bifolds can be useful where maximising the open width is the priority.

The best option depends on available wall width, budget, style and how much of the opening you want to clear. Do not widen a structural opening without appropriate design and support.

Installation Planning

The frame needs a sound, square-enough structural opening and suitable support above. It should be packed and fixed square rather than twisted to match irregular masonry. Thresholds, cills, drainage and perimeter seals need to be installed to the manufacturer’s details.

Our French door installation guide explains the sequence and the checks to make with your installer.

Maintenance

Keep frames, drainage routes and seals clean. Inspect hinges and locking points periodically and use only manufacturer-approved lubricants where required. Avoid abrasive cleaners on uPVC and coated hardware.

If the master leaf becomes difficult to lock or the pair starts to rub, alignment may need attention. Our how to adjust French doors guide covers common symptoms.

French Door Buying Checklist

• Measure the structural opening at several points.
• Confirm exact overall frame size.
• Check double- or triple-glazing variant.
• Confirm clear or other stated glass.
• Choose white, grey/white or other available finish.
• Verify master-leaf handing using the product diagram.
• Confirm opening direction.
• Check cill and threshold details.
• Review thermal and security information where required.
• Plan installation and external paving levels.

Frequently Asked Questions

Are French doors the same as patio doors?

French doors are a type of patio access door, but the term patio doors is also used for sliding and other systems. French doors specifically use a hinged pair of leaves.

What size French doors do I need?

Measure the structural opening and match it to the overall frame dimensions and fitting tolerance of the exact doorset. Do not choose by nominal width alone.

Are uPVC French doors low maintenance?

uPVC frames do not require painting like unfinished timber, but the doors still need cleaning, drainage checks and hardware maintenance.

Is triple glazing better for French doors?

It can offer different thermal characteristics, but compare the complete doorset specification rather than choosing on pane count alone.

Which leaf opens first on French doors?

The master leaf is the primary opening leaf. Check whether the product is left- or right-hand master according to the manufacturer’s stated viewing convention.

Shop French Doors

Compare the current range of uPVC French doors at JJ Building Materials by size, colour and glazing, and confirm every product-specific detail before ordering.