The new JA-48 bifold. Our high performance, easy to install door.

just aluminium bifolding doors

JA-48 Aluminium Bifolding Doors

Ultra-slim frames, low U Value and short lead times  – all from JUST £445 per leaf

JUST Aluminium have developed the JA-48 aluminium bifolding door based on the incredibly popular Alunet slimline system. The JA-48 offers market leading performance whilst remaining exceptionally strong and durable.

Ultra-slim frame

The JA-48 is one of the slimmest door frames on the market today (48.5mm frame width) with a sightline (the point two frames interlock including a 10mm gasket) of just 107mm. We can create bifolds up to 2600mm in height (we can offer doors up to 3000mm in height with a 55mm frame width) and a sash width of up to 1200mm in width – we can even create systems up to 14 door panels. 

Exceeds UK Building Regulation standards

With engineering grade hardware, the doors effortlessly open and close with a reassuringly functional and robust feel, providing an underlying sophistication and premium quality. The JA-48 exceeds UK building regulations delivering an incredibly low U-value of 1.4 with a double glazed unit (LowE, toughened 1.2 U value as standard). With a simple glazing upgrade (6.8mm toughened 1.2 U value) and 3* Ultion locking cylinder, the JA48 doors will achieve PAS24. The JA48 system can also accommodate a 44mm triple glazed unit for those demanding even higher performing thermal and acoustic insulation (our 44mm glazed unit is rated at 0.6 U value).

Pre-gasketed for faster installation

The system is fitter-friendly, offering pre-gasketed beading which massively reduces installation time. In addition, the JA-48 comes with an integrated cill and weathered threshold as standard, minimising install times and reducing the bottom frame by 25mm. This maximises the glass and enhances the streamlined appearance.

All available from only £445 per panel with UK delivery available*

*Collection from our factory is welcome. We can deliver anywhere on the UK mainland – get in touch for a competitive delivery cost to your postcode.

JA-48 Bifolding Door features at a glance

Just aluminium JA 48 bi-folding door

JA-48 Bifolding Door Spec

  • 48.5mm frame width** (width viewed front on)
  • 107mm super slim sightline (width where 2 frames meet viewed front on including 10mm gasket)
  • U values of 1.4 (with our ultra-lowE 28mm double glazing)
  • 44mm triple glazing available (glass unit rated at 0.6 U value)
  • Frame depth of 73mm (distance between the front and back of frame)
  • Up to 14 sashes (7 in each direction) 
  • Panel widths up to 1200mm per sash (700mm minimum) and maximum height of 3000mm**
  • Marine grade powder coated finish as standard
  • Weather rated standard threshold with integrated cill only 55mm high (low threshold, low threshold with rebate options also available)
  • PAS 24 security rated (with glass and locking cylinder upgrade)***
  • Engineering grade stainless steel rollers and track for ultra-smooth opening and closing
  • Easy to install – pre-gasket beading for faster, simpler installation
  • High performance weather seals

Energy efficient as standard

We hold considerable stock of standard colours and options so can offer delivery in as little as 2 weeks from order (glazed) and even less unglazed. Furthermore, the JA-48 is designed to exceed UK building regulations, offering a U value* of 1.4 with our double glazed unit and even lower with a triple glazed unit. These impressive figures help to maintain a comfortable indoor temperature while reducing energy consumption and reducing heating bills. This feature contributes to energy savings and promotes sustainability.

*Thermal performance is measured in terms of heat loss, and is commonly expressed in the construction industry as a U-value. The lower the U value, the better the insulating performance. Many other systems require triple glazing to meet a U value of 1.4 whereas the JA-48 achieves this with an ultra-low E double glazed unit.

** For sashes over 2600mm in height we use a 55mm frame.

*** As standard, there is no external access (or natural traffic door) for even numbers of panels all folding in the same direction. Please raise this with the team if external access is required. If you’re unsure whether your order confirmation provides external access, then speak to us and we will confirm.

quality bifolds
JA48 cross section
your bifolds


With one of the slimmest frames available in the UK, you can benefit from more natural light, a more modern look and improved views of your garden from within your home.

aluminium doors that keep you warm


JA48 bifolding doors from JUST Aluminium can achieve a U Value as low as 1.4 which means you stay cosy and warm on the coldest winter days and can look forward to lower energy bills for years to come!

bi-folding doors


All JUST aluminium bifolding doors can conform to PAS 24 if required, offering you the ultimate peace-of-mind for your home, family and business

Specify your doors online for an instant quote – It’s JUST so easy!

Simply input your sizes, colour and look and generate a supply only price in seconds

JUST select your colour.

JUST aluminium keep things simple – we offer 3 standard colours: Anthracite Grey, Black and White. Whilst there are hundreds of RAL colours, 99% of our clients opt for one of these three options. Whilst we can offer dual colour and other colour options, we hold these standard colours in stock, allowing us to achieve faster turnaround timescales.


THE classic aluminium bifold door colour for that sophisticated ‘Grand Designs’ look. Our most popular colour choice


Perfect for a more sophisticated, contrasting colour option or a more striking contemporary finish


Offering a more traditional look and often chosen to match existing window frames, traffic white provides an ideal alternative

Choose a threshold.
JA55 integrated cill and threshold


Our integrated cill and threshold profile (total height of just 55mm) provides full weather rating on our lowest threshold and maximises the overall sash height of the door leaf meaning more glass and less frame.

JA55 standard threshold



The standard threshold (55mm) acts as a full weather break, keeping the property dry and warm regardless of outside elements. Recommended for external bifolding doors.


Our Low Threshold (20mm) offers less weather protection but creates a seamless look. Low thresholds reduce trip hazards so are more suited for those with mobility issues or small children.


A 20mm rebate can be attached to our low threshold, making it only slightly higher at 40mm. The lip of the rebate gives extra weather protection against the elements. Also available with a ramp.

Select your cill.

The JA-48 bifold system is available with aluminium cills, pre-drilled screw ports and push-in colour matched end caps in our standard stock colours. The cill size options also include 90mm stub cill, 150mm standard cill plus larger 190mm and 230mm options. The integrated weathered threshold and cill is our most popular choice as it maximises the sash height and minimises the bottom frame by 25mm, whilst offering full weather protection – the cill is our standard 150mm.

Your configuration.

The JA-48 system is available as bifolds, but also as a single door and French doors. Bifolds can be configured as two panel* through to 14 panels. If you select an odd number of panels with all leaves sliding to one side, the system naturally creates a traffic door. If you have any questions regarding configuration, then give one of our team a call to discuss your requirements and options available.

*external access for French doors but no external access for two panel bifolds

Trickle vents required?

JA-48 is available with or without trickle vents depending on your requirements**. Each vent is 5000EA and we can provide anything from one vent per system through to one vent per sash all seamlessly housed in a colour matched head extension.

**whilst we can provide advice on ventilation and vents, it is your responsibility to discuss your specific building regulation requirements with your builder/architect/building regulations officer. 

Handles – JUST choose the perfect finishing touch

 Whatever colour door frame you choose, we have the perfect handle to match. We would recommend a matching handle to frame so the hardware is less noticeable and uniform, however chrome and satin options can add an element of sophistication.  

black bifold handles

Anthracite aluminium
lever handle

black bifold handles

Black aluminium
lever handle

white handles

White aluminium
lever handle

chrome bifold handles

Chrome aluminium
lever handle

chrome bifold handles

Satin aluminium
lever handle

Glazing – JUST the right choice

JUST Aluminium installs Low E toughened glass in our bi-fold products as standard. LowE glass is one of the most energy efficient glazing products in the UK, specifically designed to help homes reduce their energy consumption and save money on energy bills, reflecting solar energy outside on a hot day (keeping buildings cool) and reflecting heat back into a building in the winter months (keeping rooms warmer). Energy efficient glass also performs exceptionally well using the JA-48 profile and our choice of hardware, making it the perfect choice of glass for any home or commercial property. 

Key features of Low Emissivity glass

  • Improves the energy efficiency of your home thanks to its all-round balance of thermal insulation and by maximising free solar gain
  • Reduces the amount of energy required to keep your home comfortable.
  • Environmentally friendly solution, given the lower CO2 emissions associated with reduced energy consumption
  • Heat loss is significantly reduced as the coating prevents heat from escaping through the glass Helps to eliminate cold areas around your windows, making your home warmer and reducing your energy bills
  • Reduces condensation on the inner pane
  • Neutral appearance in both transmission and reflection

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