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Frequently Asked Questions

We understand that researching bi folding doors can be a complex and often draining process as there is a wealth of information, jargon and technical information to contend with. We have included our Client’s Frequently Asked Questions as well as the definition of most of the technical terms we have used throughout our site, to take some of the strain out of the process. Please do not hesitate to contact us with additional queries.


U-value measures the effectiveness of a material as an insulator. The lower the U-value is, the better the material is as a heat insulator.

Our bifolds are glazed with A-rated glass. We have the option of U value 1 or 1.2 glass in our configurations. We supply 1.2 graded glass as standard. 1.8 is the government requirement, this highlights the efficiency of our system and the standards we strive to meet.

Our system has a bottom track on which the weight of the door rests, so it is bottom rolling. We have found this ensures better stability and opening.

All our products are manufactured completely in our UK based warehouse which is currently in Luton. Our office and sales team are based in London.

A-rated, double glazing glass is used as standard in all our Express Bifolds. However, on bespoke orders there are a variation of options to choose from. We also offer integral blinds.

Provided that we offer a bespoke service either direction of opening is available. However, our stock sizes are outward opening as this is the most desired option. The outward opening system has 2 main benefits, furniture does not get in the way of opening and closing of doors and if the weather has been wet the water from the doors won’t drip inside the house when opened.

Trickle vents can be supplied at an additional cost if required. We do not fit them as standard as not all customers require this feature for aesthetic or ventilation purposes.

Aluminium is light weight yet extremely strong, has extremely low maintenance requirements, is versatile and resilient to all weather conditions. The renowned qualities of raw aluminium make it the ideal material for window, door or roof products.

Configuration Options

Imagine you are inside the room looking out, which way would you prefer for the doors to open and then stack up.

There is complete flexibility for you to design the bifolds that suit your needs. You can have all the panels opening the same way, or you can split it so that some open to one side and some the other side.

We offer a standard and low threshold option on all bespoke orders. All our stock products come with standard threshold as normal. This is often referred to as the weathered option because it is weather-rated and thus designed for external spaces. The low-threshold has a sunken cill to provide a flush floor level finish. There is no rebate for the doors to seal against and therefore it is not fully draught proof and requires an external drainage gulley.

If you want to be able to open a single panel door without having to release all other panels you require what we call a traffic door. For this function you must choose an odd number of doors to open in the direction required.

Glass Openings’s bifolds can be manufactured in over 150 RAL colours, ensuring there is a style to suit every property. The most popular colours, Anthracite Grey and White are stocked. We also offer the option of having a different colour on the inside and outside frames.

The minimum height of Glass Openings’ bi folding doors is 1800mm. The maximum height of our system is 3000mm. This is one of the advantages we hold above our competitors, as the majority of them offer a maximum height of 2.4 metres.

The minimum width per bifold is 600 mm and the maximum width is 1200mm.

Yes, integral blinds are an optional extra for all our doors. We supply only the non-cordless, magnetically operated integral blind system. Our standard and quality of glass remains the same on such orders. Please visit our “Integral Blinds” page for further information.

Compliance and Guarantee

Our standard doors meet the following regulations, Document Q and BS6375 Part 1 Weather Testing. Bespoke doors can be configured to meet PAS 24 regulations.

Our Aluminium and paint come with 10 years warranty from the extruder. Our hardware comes with 10 years warranty from it’s manufacturer. Our integral blinds come with 10 years glass and blind manufacturer’s guarantee.

we are not required by fensa to be regulated as we only carry out installations to new build properties and extensions and not replacement doors and windows.


On our Express Bifolds the lead time is within 10 working days if in stock. If out of stock then 3-4 weeks. On Bespoke Bifolds without integral blinds the delivery time could be up to 3-4 weeks, with integral blinds delivery is to be expected between 4-6 weeks.

For delivery to most parts of the UK, it is free. For delivery to some parts of the uk we charge surcharge of £100. For accurate cost for delivery please refer to the Delivery Information page.

Yes, collection is free of charge. At Glass Openings this is our preferred option.

Yes, you will be notified by our delivery team to arrange a delivery slot. You will also receive notification at least an hour prior to delivery.

If the payment has been made in full delivery can be delayed until the next available time of convenience for you.


We provide all hardware required to assemble our bi folding doors. This consists of handles, locks, keys, hinges and screws. The doors do not come with the fixtures required to install the frame as most Builders/ Installers have their preferred method and tools. The required products are also most likely to be a part of their standard tool kit and readily available also at local DIY shops. We do offer the option of purchasing an additional Fixing Kit, should your installer require this.

Yes, our doors come with comprehensive yet easy to follow installation guides. We have a series of handy videos and images that have been made to ease the process further.

We offer an installation service on all Bespoke Bifolds.

Please refer to our “Guarantees” page for an comprehensive answer to this question. [link to Guarantees page]

Technical Terms Defined

To avoid any possibility of confusion, we have put together a glossary of the terms of the terms we frequently use to describe our products. All words are relative to Glass Openings’ products and do not always conform to dictionary terms.

When the bi folding system rolls on a bottom track. Given that the majority of the door’s weight is concentrated at the bottom this ensures better stability and opening.

This locking system bolts the door into the frame and locks at multiple points at the turn of a key. It has a minimum of three locking points that all work simultaneously.

Integral blinds feature venetian style blinds in between the panes of glass that make up the double-glazed window.

Glass that has been treated with an invisible coating to dramatically reduce heat transfer and to reflect internal heat back into your property.

The measure of the effectiveness of a material as an insulator.

A barrier or insulation is placed between the interior and exterior of the aluminium door frame to prevent the flow of thermal energy between conductive materials. This ensures that heat is kept in and cold kept out.

A approved polyester powder-coat paint which is baked onto our aluminium. RAL is a paint industry colour reference, the chart offers 150 colour variations.

A form of high security locking system consisting of a central gearbox, facebar, and shootbolt that extends outward to lock it tight to the frame.

When the weight of the bi folding door is supported from the top. Given that the doors effectively hang from the top tracks, this system requires sufficiently strong lintels above the opening to endure the weight of the door.

Safety glass processed by controlled thermal treatment to increase its strength and durability. It is about four times stronger than normal glass.

A standard hinged door sash that can be used without having to open the complete bi-fold. It opens separately from the bi folding system to allow access from the outside. This is a convenient and good safety feature.

This is effectively the bottom track of the door. We offer the option of weathered and non-weathered thresholds. For external bi folding doors we recommend our weathered threshold. This consists of a sunken floor track and a small upstand lip that in turn creates a weather tight seal. The non-weathered thresholds are flush and have no lip. They ought to be used in internal or sheltered areas.

A ventilation system required legally to improve air quality inside the property.

For further clarification or assistance please do not hesitate to contact us.