Who makes the slimmest bifolding doors?

The aluminium bifolding door offers a host of benefits in the home, but what are the slimmest bifolding doors available at the door mullions? With more bifolding door systems available than ever before, if you are a homeowner looking for a quality bifolding door, there is a tremendous amount of choice. One area you may be considering is the appearance and aesthetics at the door mullion.  For the trade, this article helps you compare the majority of the UK systems, useful to compare against the products you do sell.

Slimmest bifolding doors available to buy

Who makes the slimmest bifolding doors?

One of the promoted features of the bifolding door is the ‘door sightline’. The door sightline is the visible aluminium you see on a closed set of bifolding doors.  This is where the door panels meet or referred to as the door mullion.  

Here is our table illustrating the sightline of virtually every major aluminium bifolding door system available today. See how they compare in order of slimness at the door mullion and the sightline dimension you can expect to see.

Smart Systems Visofold 600094mm
Solarlux Ecoline and Highline99mm
Solarlux SL80105mm
Dutemann FD85 (Alumil SF85)105mm
Express Bifolds XP Vision (Alumil SF85)105mm
Origin OB-49 Bifolding Door110mm
Greenways Ultra Slim Bifolding Door110mm
Schuco ASS 80FD112mm
Sunflex SF75115mm
Schuco ASS 70 FD120mm
Comar FSDX Folding Sliding Door120mm
Cortizo Bifolding Door120mm
DeWall Bifolding door by Debar120mm
StudioGlide by Eurocell (DeWall product)120mm
Alutech BF73 Bifolding Door120mm
Unifold by Arkay Windows120mm
Air 800 Bifolding Door122mm
AluK Luminia F82 Bifold Door122mm
Reynaers CF 77 SL122mm
Senior Architectural Alifold Doors123mm
Senior Architectural PUReFold Doors123mm
Sunparadise Supertherm 80 Bifolding Door124mm
Sunparadise Thermo 60 Bifolding Door124mm
Stayfix Architectural Vision Fold Doors125mm
Folding Sliding Door Company FD72130mm
Velfac 860 Bifolding Door130mm
Reynaers CF68131mm
SAPA Crown Folding Door with slim sash131mm
Smart Systems Visofold 1000132mm
Exlabesa Xlafold Bifolding Door135mm
Centor C1 Bifolding Door136mm
AluK Optio BSF70 Folding Sliding Door140mm
Sieger Bifolding Door140mm
Smart Systems Visofold 2000141mm
Metal Technology Bifolding Door143mm
Technal Ambial Bifolding Door143mm
Reynaers CF77144mm
Panoramic Slide and Turn Door145mm
Kawneer AA3720 Bifolding Door145mm
Stellar Aluminium Systems Bifolding Door146mm
Kestrel Folding Sliding Door150mm
Metal Technology System 26 HI+ Bifolding Door153mm
Origin OB-72 Bifolding Door154mm
Smart Systems Visofold 3000154mm
Alumina by Liniar156mm
Warmcore Bifolding Doors156mm
Solarlux SL70157mm
SAPA Crown Folding Door standard sash165mm
Aluprof MB System Bifolding Door166mm
Smart Systems Visofold 4000185mm

How we arrive at our list of the slimmest bifolding doors?

The data for fifty folding sliding door systems comes from the system company websites or their technical and fabrication manuals.  The above sightlines indicate the typical dimension where two intermediate panels meet. Sizes with some systems increase when a folding panel meets the traffic door if one is specified.  We excluded frameless and slide and fold doors operating on an individual moving and folding panel basis as well. Also excluded are systems that do not meet current Building Regulations.

However, there are two bifolding door systems even thinner than the Visofold 6000 bifolding door, top of the list above. We did not include these two in the list above because these are structurally glazed bifolding doors, made around the glass. The above systems are dry-glazed.

Solarlux slimmest bifolding doors

The Sieger Lux Bifolding Door.

Our research shows the overall slimmest bifolding door on the market in the UK right now, to be the Sieger Lux product. This boasts impressive 30mm wide door sash profiles with integrated locking systems. As a result, these give an overall mullion dimension of 74mm.

Unlike the doors above, the Sieger Lux bifolding door comes structurally bonded and allowing the glass to take the weight of the product, reducing the aluminium sightlines as a result.  Studying the section drawings of this product reveals thermally insulated aluminium profiles, bonded to 28mm double glazed or 32mm triple glazed units.

Square edges, slimline door components, 3-point locking system, open corner option and traffic doors are just some of the standard features you get. Minimal aluminium frames combined with high specification glass units also provide U-Values of 1.6Wm2K depending on the glass used.  As well as this, you get the expected large bifold panel sizes of up to 1.2m wide and 3m high. This is one outstanding door for aesthetics and design and well worth checking out.

The System 48 bi folding door by Fineline Aluminium.

Even thinner than the Sieger Lux bifolding door is the System 48 Bifolding Door by Fineline Aluminium of Weston Super Mare. The System 48 Bifolding door offers a remarkable 48mm sightline and beating the Sieger by quite a margin.

However, the aluminium sections are not, strictly speaking, door sash sections, and it uses different hardware for the slide and fold operation.  The locking systems are located on the rails rather than the door stiles too.  Moreover, with such narrow sections, most lock cases cannot fit in such thin sections.  While very much a bifolding door worthy of consideration, we felt the System 48 bifold as being far too different in its design to be included in our table of ‘conventional’ bifolds, that mostly share a similar construction. But it is a fantastic looking bifolding door with impressive thin proportions.

The frameless folding sliding Door.

It is worth giving a mention to the frameless bifolding door. These are minimal-framed slide, stack and fold products that, chosen correctly, provide even thinner sightlines.  If you want even less visible aluminium, then check out frameless bifolding doors.  Sunseeker doors have a mullion sightline of 38mm using a plant-on profile to cover the glass edges.

Frameless Glass Curtains by FGC of Chatham has no visible mullion and only a minimal gasket sight line where the door panels meet. Smart engineering, a patented glass spacer bar and sophisticated gaskets make these doors incredibly thin. Therefore, if you want as much glass as is possible on a bifolding door, we suggest you consider these.  A different kind of bifold in design and operation but also a contender amongst the slimmest bifolding doors.

If you are wondering why some well-known big retail brands are missing, this is because many use the above systems or variations of them. This includes well known retail companies such as:

  • Express Bifolding Doors using Schuco, Alumil and Smart Systems
  • Bifold Direct
  • Everest Home Improvements
  • Anglian Home Improvements
  • Kloeber using Schuco
  • Duration Windows using Smart Systems and Aluk

Are slimmer bifolding doors better?

No.  AluK, Smart Systems and Origin are three bifolding door brands in the UK with excellent sales, given the size of the systems companies by turnover and the volume of bifolding doors supplied. This is despite their doors not being the slimmest on the market.  It’s the same with the new bifolding door from Stellar Aluminium Systems. They too don’t have the slimmest bifold on the market but their entire suite of windows and doors is new, innovative and worthy of consideration.

Centor bifolding doors are probably one of the best on the market. Yet these aren’t the slimmest.

Ultimately a buyer and a manufacturer of bifolding doors takes many different factors into account and not just the bifolding door sightline.  However, with the bifolding door market established and with more than 30 systems available, customers have never had more choice.

Recent slim bifolding door products include the air 800, the Dutemann FD85, the Exlabesa Xlafold and the Smart Systems Visofold 6000.  The Comar bifolding door is as thin as the better known Schuco door.  All these products are designed with a narrow bifolding door sightline as an ultra-slim door is often perceived as being more desirable.

What to consider when buying bifolding doors.

The sightline is just one consideration when buying a bifolding door.  It is not just about the slimmest bifolding doors.  Here is what else is more important.

  • The overall product aesthetic and how it looks like a complete door not just in one area.
  • The more door panels, the less intrusive the mullion can appear.
  • The quality of the hardware, locks and bifolding door handles.
  • The colour, handle, configurations available and other personalisation options.
  • The security and weather performance of the product.
  • The U-Values provided if energy efficiency is important to you.
  • The guarantee available with the product.
  • Your confidence in dealing with the company providing you with the doors.

If you would like more information about the system mentioned or have any questions about bifolding doors, contact us. If you’re also considering sliding doors, take a look at who makes the slimmest sliding doors in aluminium.

Reader Interactions


  1. Adam says

    I have a South Facing garden and it can get hot, my neighbour left his phone in the kitchen and it melted, he has normal glass in his bi folds so I was looking for Triple Glazed, i’ve been told it not worth the cost and to go for Solar glass instead, thoughts please?

  2. Ruben Fourie says

    Hi. Thank you also for this article. We need a bi folding door for a 4.3m x 2.1m opening. Really want the smallest frame possible but only have around £4. 5k for the material. Is this possible? Please could you make a recommendation?

    • Nick Dardalis says

      Hello Ruben

      Due to the increasing volume of comments, we are struggling to manage these via the comment forms. Therefore, please can you use our contact form where these are managed and always responded to. Your location also helps us with suggesting a local installer and brand.

      Kind regards

  3. Lulu says

    Hi Nick

    Thanks for the wonderfully informative article.

    Due to our architect miscalculating we are having to find slider or bi-folds with the slimmest possible header sight-line. We were supposed to have a ceiling height of 2250 but now only have 1875, so every inch helps. It’s for a first floor bedroom.

    I know Origin do a 74mm header sight-line, but the increase in cost is near on £4…for one 2300 x 1875 slider. Is there another company out there which is affordable?

    • Nick Dardalis says

      Hello Lulu, thanks for your comment and sorry you’ve had trouble with your doors.

      Due to the increasing volume of comments, we are struggling to manage these via the comment forms. Therefore, please can you use our contact form where these are managed and always responded too and I can try help with a solution.

      Kind regards

  4. Vanessa says


    Really helpful to read your knowledgable write up. Please could you recommend a supplier of aluminium windows and doors in Cheshire.

    Many thanks

  5. vicky forbes-cross says

    Hi Nick,

    I don’t suppose you could recommend anyone who does thin bi-folding doors, with good heat in and out protection. Our terrace gets very very hot in summer!

    Many thanks

    • Nick Dardalis says

      Hi Vicky I think I’ve responded to you by email but summary below

      Glass by it’s very nature will create solar gain so you won’t
      stop the terrace getting hot completely, but you can help reduce the heat.
      Solar control or suncool glass are options as are integral blinds within
      the doors.

      I can suggest the below companies to get in touch with that can help you.

      Aspire Bifolding Doors
      11 Castle Parade,
      Ewell By Pass,
      KT17 2PR
      020 8224 7431
      Please speak to John Small or James Wenlock.

      FGC offer both aluminium and a frameless system as well as enclosures for
      balconies and terraces so worth speaking to them and see if they can help.
      FGC Bespoke Aluminium/Frameless Glass Curtains Ltd
      01634 567500
      17E Altbarn Industrial Estate,
      Revenge Road,
      Kent. ME5 8UD

      Hope this helps
      Kind regards,

    • Nick Dardalis says

      Very good products from Sieger at the top end of the market. We’ve seen these recently and they are well worth checking out. The good thing about products like Sieger is they come with more design flexibility compared to conventional doors.

      While thermal breaks are important to the overall performance of a product, it’s the glass of course that creates the most amount of solar gain. No products we know of come with a basic glass unit any more. But when it comes to considering the amount of heat internally a new extension will generate, we do suggest speaking with a good installer and exploring the various options for controlling glare and heat, more so on South facing elevations.

      There are presently all manner of options such as the solar control glass we mentioned earlier, tints, integral blinds and even after-market shading solutions such as those offered by Centor. Checking out the various glass supplier/manufacturer websites such as Pilkington and Saint Gobain will also provide further information.

      Hope this helps
      Kind regards,

  6. Claire says

    Hi Nick,

    I was wondering if you could help. I am looking to purchase an aluminium door for a space 2200 by 2200. A minimal sight line is important as is security, weatherproofing, solar protection and warranty. I had been looking at the traditional bifold but sight lines are not desirable so have moved towards slide and pivot (sunseekers and frameless glass curtain).

    What do you think about both in relation to my requirements?

    Also from a customer service perspective, does one stand out above the other? I have read the google reviews about poor customer service from sunseekers and admit to being put off. Also, when trying to get a quote I found my email and calls were ignored which isn’t a great start. They did however respond promptly to my architect.

    I haven’t reached out to frameless glass windows as yet.

    Are there any other companies you would recommend?

    Also, I will also have a glazed corner in my kitchen. Current thinking is to have a sliding pocket door on one side and a hinged pivot door on the other side (as it will open up against a fence). Are there any companies that will provide for this solution without having to have a fixed post in place? I would really like to open up the whole corner if possible.

    Am currently talking to Maxlight but wanted to check re options.

    Would the maxlight doors go better with the sunseekers or frameless glass curtain doors?

    • Nick Dardalis says

      Hello Claire, thanks for your question. The Frameless Glass Curtains door is excellent as an external quality door with very good security, quality and one of the lowest thresholds. The reviews of the company are also excellent over many years and we know their customer service is also very good. So do get in touch with them and have a look at their product.

      You need to ensure these frameless doors are intended for external use. We know the FGC ones are but others come mainly intended to create enclosures and glazed partitions not really meeting good U-Values and performance requirements. These doors also come with a removable corner post.

      It’s hard to comment on the corner product as not quite sure of the design you want. If the hinged door hinges on the corner then this will be more difficult, otherwise yes it is possible is the door is hinged on the wall side. Only bifolding and sliding doors come with a moveable corner post so you could have a hinged bifold leaf on the one side, but again hard to be precise without seeing a sketch.

      Maxlight we know do some fine installations, as do Sieger and others, but if you get in touch via our contact form with your location, I can suggest some others if you need other quotes.

      Hope this helps, please don’t hesitate to get in touch if you’ve any questions or need further information. 
      Kind regards

  7. Caroline Southall says

    Please supply brochure / information re minimal sight line bifold doors

    • Nick Dardalis says

      Hello Caroline, thank you for your comment. Our website is an information resource only and does not provide brochures as we cover so many different products.

      If you’d like to get in touch via our contact form we can help specifically.

      As you can see from the list on this page, we’ve covered the sightlines on all the major products and can help you choose from any of these and put you in touch with a local installer.

      Kind regards

  8. Neil says

    Hi, I was wondering if you could help. I’m looking for competitively priced bifolds which have a fairly narrow sight line and have the option for integrated blinds. Thanks

    • Nick Dardalis says

      Hello Neil, thank you for your question. It, of course, depends on your budget but would suggest the following doors all with narrow sight lines. All of these doors also suit integral glass blinds.

      Smarts Visofold 6000 bifolding doors.
      There is a new Origin door coming out in June so get in touch with us for your local Origin dealer to find out more. These are also going to be slim.
      Sunflex SF55e doors are excellent also with narrow sight lines and well worth considering.
      Schuco ASS70 bifolding doors also good.

      If you’d like to use the contact form with your location, I can try put you in touch with some local suppliers.

      Hope this helps
      Kind regards

      • Neil says

        Hi Nick, thanks for taking the time to reply and apologies for the delay. I’m near Canterbury, Kent.

      • Raj says

        Hi Nick, you mention a new Origin bifold door coming out in June.

        I’ve been ringing the Origin sales line over the course of June and none of them know of a new bifold door coming out.

        Any ideas??

        • Nick Dardalis says

          Hi Rajh, I was referring to the Origin sliding door OS-77 available now through a select number of retailers.


    One of the considerations listed is Guarantee period.
    Origin offer 20 years with Aluk offering 10.
    Should the Guarantee period be a significant factor of choice ?

    • Nick Dardalis says

      Hi Martin, the fair answer is no it shouldn’t, mainly because products such as Origin 20 years, Air Doors 25 years are fine doors but the vast majority of bifolding door products do as well as these excellent bifolds with 10 years. Ultimately it is down to the homeowner and how much the guarantee matters in the purchasing decision. For example, if you are renovating a home for long-term living and then the guarantee is bound to matter more than perhaps if you’re looking to sell the home in the near future.

      Any well made and correctly installed product should be reliable in the long term.

      We also have to credit companies such as Origin and Air 800 bifold doors because the reason they offer this type of guarantee is down to the fact that only these companies make their doors. For this reason, they are able to stand by their excellent manufacturing and offer a longer guarantee than the other doors on the market made by many different manufacturers. Again, this is a good reason to consider these types of doors.

      Hope this helps, please don’t hesitate to get in touch if you’ve any questions or need further information. 
      Kind regards

  10. Shirley says

    You note in your article that some big retail brands are missing from the list , as they use one (or a variant of) the systems listed. Can you tell me which system Kloeber uses as they make out they design and manufacture their own.

    Great information on your site, thank you .

    Many thanks

    • Nick Dardalis says

      Hi Shirley, we understand Kloeber uses the Schuco system, ASS70FD bifolding door.
      Thanks for the kind comments about our website.

      Kind regards