French Door Sizes UK: How to Choose the Right Width & Height

French doors are available in a wide range of sizes, which is useful for replacement projects but can make the phrase standard French door sizes UK confusing. A complete uPVC French doorset is measured by its overall frame, not by simply adding together the width of two individual door leaves. The frame, meeting stiles, cill and fitting tolerance all affect the opening required.

This guide explains how to compare sizes in our French doors range and how to plan a structural aperture around the exact product rather than a guessed nominal dimension.

Is There a Standard French Door Size?

There are commonly manufactured widths and heights, but no one size fits every UK property. Modern uPVC systems are offered in stepped overall widths, while older timber French doors or patio openings may have bespoke dimensions.

If you are replacing an existing set, measure the structural opening. If you are building a new extension, choose the doorset early and create the opening to suit its documented frame size and fitting allowance.

Overall Frame Size Matters Most

With a complete doorset, the frame is the component fitted to the building. That makes the overall frame width and height the critical product dimensions. Individual glazed leaf sizes are not normally used to size the masonry opening.

Check whether the listed height includes the cill. A cill can add projection and may affect the installed height depending on the manufacturer’s dimension convention.

French Door Widths in the Crystal Range

Our Crystal uPVC French doors are offered in multiple width variants rather than one fixed standard. For example, the Crystal UPVC White French Door Clear Double Glazing Left Hand Master includes several metric size options.

This means you can often select a frame that suits an existing opening more closely, but every variant still needs to be checked against the actual aperture.

French Door Heights

Complete external doorsets commonly sit around familiar patio-door heights, but exact product values vary. Thresholds and cills can change the installation detail, so use the listed frame height and the fitting instructions together.

If internal flooring or external paving is unfinished, establish the final levels before setting the height of the structural opening.

Why Two 700mm Leaves Do Not Mean a 1400mm Frame

The complete frame includes outer profiles and the meeting arrangement between leaves. Therefore, calculating overall size by doubling an imagined leaf width can be inaccurate. Use the manufacturer’s actual frame dimension.

Likewise, a 1400mm structural opening does not automatically accept a 1400mm frame because fitting space is required around it.

Structural Opening Size

The structural opening needs to be slightly larger than the doorset in the way specified by the manufacturer so the frame can be packed, fixed and sealed. Take width measurements at three points and height measurements at three points, then check diagonals.

Our French door measuring guide explains the complete survey process.

Why the Narrowest Measurement Matters

If an opening is 1505mm at the top and 1495mm at the bottom, the frame has to fit through the tighter part. However, do not simply subtract an arbitrary allowance from the smallest figure. The correct ordered size still depends on the specific system and installer requirements.

A significantly tapered opening should be corrected rather than relying on a distorted frame installation.

Double- vs Triple-Glazed French Door Sizes

Products with different glazing can sometimes share similar frame dimensions, but do not assume every double-glazed size has an identical triple-glazed counterpart. Check the variant list for the specific product.

The Crystal White Triple Glazed French Door and double-glazed version should be compared as separate products for size and specification.

White and Grey Frame Sizes

White and grey/white variants may be offered across similar dimensions, but exact availability can differ. If you are matching anthracite-style external windows, select the colour after confirming the needed size exists in that finish.

Do not compromise the fit to get a preferred colour. The correct frame size and configuration should come first.

Master Leaf and Size

Frame width does not tell you which leaf is the master. The handing is a separate configuration. Our current Crystal products include left-hand master versions, so confirm that this suits the room and access route.

Master-leaf position is especially important in narrower French-door sets where the everyday opening leaf may be used frequently.

Opening Direction and Clearance

Door size also affects how far each leaf projects when open. A wider pair can have larger leaves depending on configuration, so measure the swing area and check for walls, furniture, patio steps and planters.

A wide opening is only useful if both leaves can actually open as intended.

Cill Dimensions

Our product titles can include a 150mm cill. This refers to the cill configuration, not simply the door width. Check projection, installation height and how the cill meets exterior paving.

Do not cover drainage outlets or bridge weatherproofing when landscaping after installation.

Replacing Old Timber French Doors

An old timber frame may have different profile widths and installation gaps from a new uPVC system. Removing trims can reveal more of the true structural opening. Measure that opening rather than copying the outer visible dimensions of the old timber frame.

Plan for making good around the new frame because internal architrave and external sealant lines may change.

Replacing Sliding Patio Doors

A sliding frame may occupy the same wall opening but use a very different threshold and frame profile. Measure the structural aperture and check swing clearance for the new hinged leaves. Furniture that was safe beside a slider may obstruct French doors.

New-Build and Extension Openings

Choose the exact doorset before the builder finalises the aperture. Provide the frame dimensions and required fitting tolerance, along with threshold and finished-level details. Coordinate structural support above with the final width.

This reduces the risk of having to pack out an oversized opening or alter a new wall to accommodate a stock frame.

French Door Size Checklist

• Exact overall frame width.
• Exact frame height.
• Whether height includes cill.
• Frame depth if relevant to reveals.
• Structural opening at top, centre and bottom.
• Structural height at three points.
• Diagonal measurements.
• Manufacturer fitting tolerance.
• Finished floor and paving levels.
• Master-leaf handing.
• Opening direction and swing space.
• Glazing and colour availability in the required size.

Frequently Asked Questions

What is a common French door width?

French doors are sold across multiple widths rather than one universal standard. Use the actual frame variants available and match them to your opening.

Is the product width the same as the structural opening?

No. The frame needs an installation allowance around it. Use the manufacturer’s required aperture or installer survey.

Are French doors measured including the frame?

Complete uPVC French doorsets are normally listed by overall frame dimensions. Always confirm the dimension definition on the product page.

Can I alter uPVC French doors to make them narrower?

No, a factory-made uPVC frame should be ordered in the correct size. It is not trimmed like a timber leaf.

What if my opening falls between two sizes?

Ask the installer whether the opening can be adjusted appropriately or whether another product size is a better fit. Do not overpack or distort the frame to compensate.

Find the Right French Door Size

Compare the available dimensions in our uPVC French door collection, then use our French doors buying guide to choose glazing, colour and configuration.