Bi Fold Doors Buying Guide: Sizes, Materials & What to Check

Bi fold doors can transform an extension, kitchen or living space by opening a much larger section of wall than a conventional hinged door. They are also a significant purchase, so it pays to understand the opening size, panel configuration, material, glazing, threshold and installation requirements before you order. This complete UK bi fold doors buying guide explains the main decisions in the order they should be made.

JJ Building Materials stocks bi fold doors including aluminium LPD Doors AluVu systems in several widths. Use the individual product page and manufacturer fitting information as the final reference for exact dimensions, handing, glazing and supplied components.

Start With the Structural Opening

The structural opening, sometimes called the aperture, is the space into which the complete bi fold frame will be installed. Do not order from a rough wall-to-wall estimate. Measure the width at the top, middle and bottom and the height at the left, centre and right, then check diagonals and level.

The ordered doorset needs the fitting tolerance specified by its manufacturer. Do not deduct a generic amount from the aperture because tolerances vary between systems. Our how to measure for bi fold doors guide covers the process in detail.

How Many Panels Do You Need?

Panel count affects the way the doors stack, the size of each glass panel and how the system looks when closed. A wider opening can normally accommodate more panels, while smaller systems use fewer. The exact configuration available depends on the manufacturer and overall size.

Think about where the stack will sit when the doors are fully open. A configuration that folds to one side can keep the opposite side clearer, while other systems may split panels across both ends. Check the actual product diagram rather than assuming all bi folds operate the same way.

Aluminium Bi Fold Doors

Aluminium is widely used for external bi fold systems because it combines relatively slim frame profiles with the strength needed to carry large glazed panels. It is also factory finished and requires different routine maintenance from timber. However, performance still depends on the complete system, including thermal breaks, glazing, seals and installation.

Our range includes the LPD Doors AluVu 8ft Aluminium Bi Fold Door, along with 6ft and 10ft options. These examples make it easier to compare real frame widths before deciding what opening to create.

Bi Fold Door Sizes

There is no single “standard” bi fold door size. Systems are available across a range of overall widths and panel configurations. The important measurement is the complete frame size stated for the product, not an individual panel width or a nominal feet-and-inches description.

Our bi fold door sizes UK guide explains how to compare product dimensions with your structural opening and why the opening should be prepared to suit the actual doorset.

Glazing: What to Compare

Large glazed areas make the glazing specification important. Check whether the system is supplied glazed, the stated glass type, and any product-specific thermal or safety information. Avoid assuming every aluminium bifold uses the same glazing specification.

For projects with a required thermal target, use the declared information for the exact doorset. The complete installed product, not the glass alone, determines the performance of the opening.

Opening Direction and Configuration

Bi fold systems can be configured to open inward or outward depending on the product. External-opening systems keep the folded stack outside the room, which can be useful where internal floor space is limited, but you need enough patio or garden clearance. Inward-opening systems have the opposite trade-off.

Check furniture, curtains, external steps, drainage channels and nearby walls. The panels need space to travel and stack without obstruction.

Left or Right Handing

Some products are offered in left- and right-hand variants. This can describe the position of a traffic door, the direction of the main opening or the stack arrangement, depending on the manufacturer. Use the product diagram to identify the correct variant.

Do not rely on a generic definition of “left hand” from another brand. Handing mistakes are difficult to correct once a complete system has arrived.

What Is a Traffic Door?

A traffic door is a panel designed to operate like a conventional single door without folding the entire system. It can be useful for everyday garden access in colder weather or when you do not want to open all panels. Not every configuration includes one, so check the product design.

Where a traffic door is important to how the room will be used, make it part of the buying decision before you choose the panel layout.

Threshold and Floor Levels

The threshold detail affects weathering, accessibility and the transition between internal flooring and external paving. Flush-looking installations need careful design because drainage and weather resistance still have to be managed.

Know the finished floor levels on both sides before the doorset is fitted. If paving will be installed later, make sure it does not cover drainage routes or bridge the intended weather detail.

Thermal Performance

Because bi folds contain a large area of glazing, buyers often focus on energy efficiency. Compare the manufacturer’s declared whole-product thermal information where available rather than looking only at the glass. Frame design, thermal breaks, seals, panel count and installation all affect real performance.

For new openings, extensions and other regulated work, confirm the project requirement with the designer or building control professional.

Security and Locking

Security depends on the complete doorset and how it is installed. Check the locking arrangement, cylinders, handles and keeps provided with the exact product. Frame fixing into the building is just as important as the hardware on the panels.

Do not modify locking components or add accessories that interfere with the tested or warranted system without manufacturer approval.

Bi Fold Door Colours and Finishes

Aluminium systems are commonly powder-coated in contemporary colours such as black or anthracite grey. Choose a finish that coordinates with existing windows, roofline, cladding and interior joinery. Remember that the inside and outside colour may not always be the same on every product.

Compare actual product photography and colour descriptions, but allow for screen differences. Where an exact colour match is critical, use manufacturer colour references.

Planning the Installation

A bi fold frame must be installed square, level and correctly supported. The structural opening also needs the appropriate lintel or support above. If you are creating or widening an opening in an external wall, structural work should be designed and completed before the doors arrive.

Our bi fold door installation guide explains the planning sequence, but high-value glazed systems are usually best fitted by an experienced installer.

Maintenance and Adjustment

Keep tracks and drainage channels clear of debris, clean frames with suitable products and inspect hinges, rollers and seals periodically. Avoid aggressive chemicals or abrasive pads on coated aluminium.

If panels begin to rub or become difficult to lock, diagnose alignment before forcing the hardware. Our bi fold door adjustment guide covers common symptoms and maintenance checks.

Bi Fold Door Buying Checklist

• Structural opening width and height measured at several points.
• Opening checked for square and level.
• Exact overall frame size confirmed.
• Panel count and stack direction selected.
• Left/right handing checked against the manufacturer diagram.
• Traffic door requirement considered.
• Inward or outward opening confirmed.
• Glazing specification reviewed.
• Threshold and finished floor levels planned.
• Thermal performance checked where required.
• Installation and structural work scheduled.

Compare Real AluVu Bi Fold Door Sizes

JJ Building Materials offers several LPD AluVu sizes, including the LPD Doors AluVu 6ft Aluminium Bi Fold Door and LPD Doors AluVu 10ft Aluminium Bi Fold Door. Comparing these actual frame dimensions is more useful than relying on a vague “small, medium or large” bifold description.

Frequently Asked Questions

What size bi fold doors do I need?

Measure the structural opening and compare it with the overall frame dimensions and fitting tolerance specified by the manufacturer. Do not order by panel width alone.

Are aluminium bifold doors suitable for extensions?

They are commonly used in extensions, but the exact product must meet the project’s structural, thermal, glazing and installation requirements.

Should bi fold doors open in or out?

It depends on the product and available space. Outward opening preserves internal space; inward opening avoids using patio space. Check the exact configuration offered.

Can bifold doors be adjusted after fitting?

Many systems provide some hardware adjustment, but the method is product-specific. Persistent problems can indicate frame or structural movement and should be assessed properly.

Do I need a professional installer?

For external aluminium bi folds, professional installation is usually a sensible choice because the frame must be accurately aligned, weather-sealed and integrated with the building opening.

Shop Bi Fold Doors

Compare our current aluminium bi fold doors by overall size, colour and handing, and confirm the exact product specification before preparing your opening.