Aluminium windows and doors on a modern house

Frequently Asked Questions about AluK windows and doors

Below we have answered some of the most common questions asked by homeowners. If you have a question that is not listed, we will be happy to answer it – call us on 01291 639 739 or send us a message and we will get back to you. 

To expand on these FAQs further, please take a look at our All in the Details link section, which is filled with informative articles on aluminium windows and doors.  

  • How secure are bifold doors? 

In addition to the inherent strength of aluminium, our bifold doors (BSF70 and Luminia F82) combine security hinges and multi-point locking systems with heavy duty rollers to provide security. Our bifold doors are tested to PAS 24, the industry standard in security, and certified under the Secured By Design scheme.  

  • What is the difference between aluminium bifold doors versus sliding doors? 

Both are used to open up inside spaces and make the most of external views. Bifold doors fold open in a concertina motion, and remain stacked at one or both sides of the opening. Sliding doors slide open using rails. With less frames, they bring in more light and panoramic views, while the actual opening itself is smaller than that of a bifold door. The choice depends on the style of property and the use of the room itself.  

  • What is floating mullion on a bifold door? 

Floating mullions are used for aluminium sliding or bifold doors when the number of door panels is even (2,4,6) and they all slide/fold in one direction. The floating mullion adds an extra aluminium profile and sight line to the locking side of the door.   

  • What is a floating corner on a bifold door? 

A floating corner is a popular feature in new-build properties or extensions where the ceiling has been reinforced to allow a completely open corner, usually a kitchen or reception room. With no corner pillar, the bifold can be installed with a floating corner post, which opens fully from the corner to both sides. This feature still delivers all the safety and security you would expect from a bifold door, while giving you uninterrupted views and that popular outside-in living.   

  • What is the maximum height and width for a bifold door? 

The maximum leaf height is 2600mm with 1200mm width, although in some situations they can go up to 3000mm maximum height. The site design wind load that the doors are subjected to will influence the maximum height and width [per panel] to which the doors can be manufactured. 

  • Are bifold doors energy efficient? 

All of our bifold doors offer high performance and market-leading energy efficiency! Boasting low U-values, you can enjoy a much-reduced carbon footprint and save on your heating bills.  

  • Are aluminium front doors safe? 

Due to aluminium’s natural durability, it is a perfect choice for front doors as it will never rust, peel or flake. Tested to PAS 24, the industry safety accreditation, and certified under the Secured by Design scheme, our doors feature both multi-point locking systems to keep intruders out and have a cloaking feature that conceals locks and prevents any access to locking points.   

  • What colour windows and doors can I have? 

The most popular colours amongst our customers are grey and black, although colour choices can be influenced by design trends. Due to our powder coating process, we offer our products in any RAL colour (which means almost any colour under the sun). We also offer a curated collection of popular and classic colours. Price can be a deciding factor, as non-standard colours are often a higher cost than colours kept in stock. If you would like to match the colour perfectly with your décor, you can choose a dual colour windows/doors – one colour on the inside and a different colour on the outside.

  • Are aluminium windows better than UPVC? 

Yes, undoubtedly aluminium is more durable and requires less maintenance than UPVC. Aluminium windows and doors are resistant to weather, corrosion- free and they won’t crack, rot or swell like UPVC over time. They also offer slimmer sightlines and a more modern, high-quality appearance than UPVC.   

  • What are mullions and transoms? 

Both elements are part of the aesthetics of a window/door. A mullion is a vertical element that forms a division between the units of a window or door. Its primary purpose is to provide structural support to the window and the glazing. When used to support glazing, mullions are often teamed with horizontal elements called "transoms", which divide an opening's upper part into one or more additional lights.  

  • Do all AluK products meet the latest building regulations? 

Yes, all of our products fully comply with the latest building regulations. These regulations are different for new build homes and existing dwellings. New build homes are subject to stricter building regulations, in order to meet carbon reduction targets. Existing homes are not subject to such energy targets, though all of our windows and doors will offer energy-efficiency and keep your home warm and dry. For specific U-Values or performance specifications, see our individual product pages. 

  • Which is better bifold or sliding door? 

This will come down to your personal preferences and how you want to use the particular space. Of course, it will also depend on how much available space you have and how much of an opening you prefer. 

  • What is a U-Value? 

U-value measures the heat transfer rate in doors, windows, walls, floors and roofs. It is usually expressed in W/m2K which is watts per square metre per degree Kelvin. In general, if the U-value is a smaller number, it means that your heat loss would be less. For example, if a window has a U-value of 1.6 W/m2K and another has a value of 1.3 W/m2K, the lower U-value window will be more energy- efficient.   

  • Is the coating on your aluminium profiles suitable for a coastal home/marine environment? 

A property in a coastal location is more exposed to the extremes of the British weather compared to a property inland. At AluK, we use a powder coating method to paint and protect the aluminium doors and windows which ensures they are suitable for windier and wetter conditions.  

  • How do I get a quote? 

Call us on 01291 639 739 or email us at: with your name and postcode and we will get back to you shortly with the name of a fabricator in your area from our extensive dealer network.  

  • Do I need an appointment to visit the London Design Studio? 

With the ease of Covid-19 measures, we are looking forward to opening our London Design studio this summer. As we will have to monitor the number of people in the building at the same time, visits are on an appointment-only basis. To arrange a visit please email us at:  

  • How do you clean aluminium windows? 

For cleaning your windows, you could use a light, soapy solution and a non-abrasive cloth to wipe off the dirt. Avoid using an abrasive cloth and solvent based cleaning products. Your installer should advise you of the best cleaning routine when they complete the installation. 

  • What is a thermal break in aluminium windows? 

Thermal breaks work on the same principle as a gas-filled double or triple glazed unit by introducing a low conductive material to prevent conductive thermal energy loss from either the inside to the outside or vice versa. All AluK windows feature a unique polyamide thermal break design to improve thermal performance, ensuring your home is warm and energy-efficient.  

  • What is an aluminium sliding door? 

A sliding door is characterised by a slim aluminium frame and a large glazing which allows opening up your home to the outside by sliding one or more doors open along different types of rails. With narrow profiles, sliding doors are the perfect option to enjoy the view outside and bring maximum light into the room. 

  • What is the maximum width and height for AluK sliding doors? 

The maximum height and width are 3500mm. This depends on the use of the room, the design and wind load. 

  • Do aluminium sliding doors have good thermal performance? 

AluK aluminium sliding doors are very energy efficient due to their thermally broken profiles. The sliding doors will keep your home warm and help you reduce your energy bills.  

  • Are sliding doors better for views? 

In general, sliding doors are better for views because they have more glazing and less aluminium frame. The vertical mullion on a sliding door is slimmer than other types of doors. Two panel sliding door has one vertical mullion and three panel door has only two vertical mullions which guarantees you will be enjoying uninterrupted views.  

  • What is the difference between an inline and a lift and slide door? 

When it comes to choosing the right sliding patios for your home or project, the options are either inline or lift and slide patio doors. They both look the same when closed, but the key differences are in the sliding and opening mechanism. The panels of inline sliding doors sit on top of rollers which are in permanent contact with the bottom track, and they use the weight of the doors themselves to glide backwards and forwards. Lift and slide doors work in a different way. It is the panels themselves which sit on the track and they only move a few millimetres up onto the integral rollers when you turn the handle 180° and activate the mechanical gearing. Read our blog for further information. 

  •  Is aluminium corrosive? 

Aluminium does corrode but that’s what makes it such a perfect material for construction. It doesn’t rust in the way that iron and steel does. Aluminium corrosion is aluminium oxide, an extremely thin and very hard protective coating which forms naturally when untreated metal meets an oxidising environment. It is this layer of grey or powdery white aluminium oxide which actually protects the aluminium underneath – and it is completely different from the rust which forms and flakes on iron and steel, exposing the substrate to damage.

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If you have a question that is not listed, we will be happy to answer it – call us on 01291 639 739 or send us a message and we will get back to you.