Request a quote Quote

Frequently Asked Questions

When choosing your Bi-folding Doors, Doors or Windows, we realise you'll have lots of questions to make sure you choose the best option available to suit your requirements. We've therefore put together a selection of our most Frequently Asked Questions to help you on your way. However, if your question hasn't been answered please do not hesitate to contact us to speak to one of our door or window experts. Please call 01953 423 423.

Bi-folding Doors

Q: Can I have a low threshold (recessed) track?

We do offer a fully flush track with our bi-folding doors that can be completely recessed into the floor leaving only a 5mm sloped rise and fall to and from the centre. The sealing method on this track option is a double brush pile so water drainage and driving wind has to be a major consideration on door installation.

Low threshold tracks are available on all our bi-folding door systems - on some you can even have a low threshold whilst still maintaining the weather rating (on these you will require a difference of 10-15mm between the inside and outside floor levels)

Q: Why do I need horizontal transoms?

Transoms (a horizontal crosspiece over a door or between a door and a window above it) are required if the height of the door exceeds 2500mm. They are required for the stability of the bi-folding door to stop the panels from flexing.

Q: Do I need trickle vents?

It is best to check with your local authority/building control as to whether or not you may require trickle vents with your bi-folding doors; this may vary dependant on the situation. Trickle vents are usually required if there is no other form of ventilation in a room.

Our in-glazed trickle vents provide ventilation of 4100mm² equivalent area (as per BS EN 13141-1:2004) per metre of vent. Our through-frame trickle vents provide ventilation of 2500mm² equivalent area (as per BS EN 13141-1:2004) per vent.

Q: Are the folding sliding doors hung from the top or the bottom?

Most of our bi-folding door systems can either be top or bottom rolling, however tall doors and faceted doors do need to be top hung.

Q: Can you manufacture faceted doors?

Yes, this is available on our SFK70 aluminium bi-folding door and our SFK69 timber bi-folding door system. To be able to price these we will require the width and height of each panel as well as the radius of the curve.

Q: Do Sunfold windows and doors comply with Secured by Design requirements?

Secured by design is a police initiative which focuses on crime prevention at the design, layout and construction stages of homes and commercial premises. The robust construction of the Sunfold Systems combined with concealed multipoint espagnolette locking and high performance security devices mean Sunfold’s systems offer exceptional levels of security.

Sunfold Systems SFK-70 premium aluminium bi-folding door is currently in the process of testing to achieve the Secured By Design accreditation. Please watch this space for exciting updates regarding the product development.

For enhanced security performance requirements, Sunfold Systems are proud suppliers of INTERNORM windows and doors to compliment our bi-folding products. These can be supplied in accordance with BS7950/PAS24 “Secured by Design” standards.

Doors & Windows

Q: What are your standard door and window sizes?

We have no standard sizes as all our bi-folding doors, interior and exterior doors and window products are bespoke.

Q: What is the weather rating on your door and window products?

All our external bi-folding doors, windows, exterior doors and roofing products carry a severe weather rating.

Q: Do you supply windows to match your doors?

Yes we supply bespoke fixed or tilt and turn windows tilting and opening is for ease of ventilation and cleaning) in both composite and aluminium to complement our doors. Please contact us if you would like a quotation.

As distributors of Internorm® products, our range of composite (timber with aluminium cladding) and also PVCu (which can also be combined with aluminium cladding) products are extensive. Excellent insulation 'u' values can be achieved, to passivhaus standard if required, along with excellent soundproofing

For further information please contact us by e-mail at

Q: Can you supply trade customers?

Yes we often deal with trade clients and have a pricing structure to offer trade prices.

Q: Do you deal with large commercial orders?

Yes. We have the facility to deal with large scale projects. Please contact as at with your project plans and our team of experts will be on hand to offer advice and a no obligation quotation.

Q: Do you have a showroom?

Yes we have a showroom in Wymondham, Norfolk. Both can be viewed on an appointment only basis to ensure that someone is available to help you. Contact us for more information or to make an appointment.

Sunfold Systems also has a permanent exhibition in the National Self Build and Renovation Centre in Swindon. We exhibit each year at national shows, contact us for details of the next planned event. We also have a network of customers who are very happy to open their homes for other customers to see their bi-folding doors, interior doors, exterior doors or windows.

Examples of our door and window products can also be seen at Kingspan Potton’s Self Build Show Centre in St Neots, Cambridgeshire.

Colours & Finishes

Q: What standard/stock colours are your folding sliding doors, sliding doors, stacking doors and windows available in?

Standard and stock colours are different for each door and window system we offer using mainly RAL and anodised standard finishes.

Any semi-gloss and silver anodised aluminium EV1 are standard with our bi-folding door systems SFK70, SFK70 Square and SFK82 (aluminium side), and also with our sliding stacking door systems the SFK25 and the SFK28.

RAL 7016 matt (anthracite grey), RAL 9016 matt (traffic white) and DB703 (dark metallic grey) are additional standard colours available for the SFK70 and SFK70 square system.

RAL 9016, 9010, 1013, 6005, 8017, 7016, 7040 and silver anodised aluminium EV1 are standard on the SFT30 internal bi-folding door system, and the SFT70 and SFT140 sliding door systems.

Dual colouring is available for doors and windows so that the appearance outside is different to inside.

We are able to offer any RAL powder coat non-stock finish on our aluminium door and window frames. Non-stock colours do carry an additional charge. A full list detailing all RAL colours can be found here. Please contact us if you require further information.

Q: What timber choices are available for wood doors and windows?

Meranti, Pine and at an additional charge, Oak.

Q: What are the standard Sikkens stains and finishes on the timber doors and windows?

Light oak, dark oak, teak and mahogany Sikkens’ stains and clear lacquer are standard timber door and window finishes, however, clear lacquer cannot be applied to the external surface of timber doors or windows.

Not all finishes are standard on all timber types. Clear lacquer is for pine and oak. Light oak, dark oak and teak Sikkens’ stains are standard finishes for oak and meranti doors and windows. Mahogany is also a standard finish for meranti.

White painted finish (RAL 9016) is a standard finish on pine and meranti doors and windows. Dual colouring is available on our doors and windows so that the outside and inside can be different. We are also able to offer any RAL colour painted finish or Sikkens stain on our timber door and window frames as a non-standard colour at an additional charge.

Q: Do you offer marine condition coatings on your aluminium door frames and is it certified?

Auminium can be coated to marine conditions and is certified by Qualicoat to meet the requirements for 'Seaside Class'.

Marine treatment protects against saline environments. Frames are protected from corrosion by a specialised process that increases the bond between the powder coating and the frame.


Q: Can you provide in-glazed venetian blinds?

Yes we can supply in-glazed venetian blinds for any system which will incorporate 28mm double glazed units such as windows, bi-folding doors and sliding doors with small panels. The blinds sit within the cavity of the double glazed unit, standard slat colours include white, silver and cream. We are able to offer venetian blinds with battery operated electric and manual cord controls.

Q: What glass do you use?

Our standard 28mm unit comprises two panes of 4mm clear toughened glass, with an argon gas filled 20mm cavity. The inner pane is equipped with a Low E (soft coat) thermally efficient coating. Glass units are manufactured to BS62606A and BS5713.

We also offer PLANITHERM ONE glass. This is a low-E glass offering the lowest centre pane U-value in the SGG PLANITHERM family providing excellent thermal insulation for the most demanding of glass specifications. PLANITHERM ONE has an optimum centre-pane U-value of 1.0W/m2K and can comfortably meet current Building Regulations by improving whole window U-values for all frame types. It makes considerable reductions in heating over standard glass and is an environmentally friendly solution, given the lower CO2 emissions associated with reduced energy consumption.

PLANITHERM ONE can be combined with our in-glazed manual or battery operated electric blinds. Triple glazing options are available on select products, contact us to find out more. We are also able to supply our systems with specialist glass types on request.

Q: What are U-values?

U-values measure how well a building component, such as a window, keeps heat inside a building. Basically the lower the U-value - the better the insulator. In the UK all U-values are quoted as W/m²K.

Thermally-broken aluminium door systems, such as the SFK70, have a general U-value of 1.6 W/m²K to 1.8 W/m²K depending upon the system size and using our standard glass units. U-values as low as 1.4 W/m²K can be achieved using Planitherm One® glass (based on 1.1m wide x 2.4m high).

Timber (SFK69) and Aluminium clad timber (SFK82) door systems have a general U-value of 1.5 W/m²K to 1.7 W/m²K depending on the system size and using our standard glass units. U-values as low as 1.2 W/m²K can be achieved using Planitherm One® glass (based on 1.1m wide x 2.4m high).

In some cases on Sunfold Systems products triple glazing can be used, which reduces the U-values achieved even further. Contact us for further information.

As distributors of Internorm® products, our range of composite (timber with aluminium cladding) and also PVCu (which can also be combined with aluminium cladding) products are extensive and have excellent insulation 'u' values. These can be utilised to achieve passivhaus standard.

More details about U-values can be found on the RIBA website by clicking here.

Q: What is document L and do you doors and windows comply?

Document L is the part of the Building Regulations that sets the standards of energy efficiency in buildings. All our bi-folding doors, external doors and window systems comply with the revised part of Document L in April 2010.

Payment & Warranty

Q: What payment methods do you accept?

We welcome payment by BACS. Our bank details can be found on our invoice.

We accept the following credit/debit cards over the phone – VISA debit or credit, MasterCard debit or credit, Electron, JCB, Maestro, Solo and American Express.

We will accept cheques - however, we ask that you allow up to ten working days for this process.

Q: What are your payment terms?

Should you wish to place an order we require a 30% deposit with confirmation of your requirements, 60% becomes payable 14 days prior to delivery and the final balance payable prior to delivery or on completion of installation.

We accept most forms of payment: cheque, BACS, credit and debit cards. All payments made using a UK credit card will be subject to a 1% surcharge, cards registered outside of the UK will be subject to a 2% surcharge. There are no charges for payment made using a UK debit card.

Q: Can I have a price list?

We don't offer a price list as all our bi-folding doors, interior doors, exterior doors and windows are made bespoke which affects the pricing, we will however be happy to provide you with a quotation if you could inform us of the width and height that you require. Alternatively you can contact us with your sizes and the system type you would like a price for.

Q: What is your warranty period?

On orders that are supplied and installed by us, we guarantee the product in its entirety as well as the integrity of the installation. These are covered for a period of five years and on additional systems, for example, the SFK70 aluminium bi-folding door for 10 years.

Supply and delivery orders are also covered for either five or ten years, dependent on the product, if a customer experiences a breakage, malfunction or is having difficulty in operating the door or window system as a result of manufacture defects. However, if problems arise as a result of poor or incorrect installation, we do offer a chargeable service to rectify any problems.

Some additional components such as in-glazed blind controllers and electrical roof vent openers can have a reduced warranty period. Any variations like this will be detailed on the guarantee certificate issued once the job is complete.


Q: What are your delivery lead-times?

Due to the exceptionally high quality of our bespoke products we do not offer set lead times. Each job is unique and therefore the time it takes to produce and install can vary significantly depending on the system type, colour and order complexity. We always strive for the shortest possible lead times, but without compromising on our high standards of manufacture or installation. Please contact us for more details.

Our SFK20:20 system is currently available with improved pricing and lead times as short as 4 weeks.

Q: Do you deliver abroad?

Yes we are happy to arrange delivery or installation worldwide - we will need the full site/delivery address before being able to price this.

Customer Service

Q: Can Sunfold provide a full site survey?

Yes, a full technical on-site survey can be provided to ensure all aspects of the building, the environment and legislations are taken into account, for a nominal fee.

Q: Can Sunfold provide me with CAD drawings?

Yes if required. CAD drawings will show the overall design of your property incorporating the chosen Sunfold System, along with showing structural dimensions, manufacture dimensions and any extra ancillaries. If you choose to have a site survey, CAD drawings are included as part of the package.

Q: Can Sunfold supply and install?

Yes, we can accommodate any requirements you have – supply only, supply and install, survey and supply or the complete package of survey, supply and install. Your Sunfold sales representative will be able to advise you.

Q: Who do I contact if I have a problem or query?

Good customer service is immensely important to us. We will be on hand to answer any questions you have at any stage of the project. Contact Sunfold’s Head office telephone number: 01953 423423. You will be directed to the correct department depending on the nature of the enquiry.

Q: How can I provide feedback on my experience with you?

We love to receive feedback, without it, we can’t improve. At any time you can call us on 01953 423423, e-mail us at or use the contact us section at the top of this page.

Once we have finished your work, we will send you an e-mail asking you to complete an on-line survey. We would really appreciate you spending a few moments answering the questions. It is only with your feedback that we can continue to maintain and improve our business. If your job is finished, but you have not completed a survey, please do, all entrants are entered into a free prize draw. Click on the relevant link below. Many thanks.

Supply only

Supply & fit

Supply, fit & survey

Supply & survey

Q: How can I obtain technical details on your products?

Many of the products on the site have technical details available. To access to our technical documents please create an account by clicking the red button at the top of any page and filling in the details. Wait for activation and then access the specific technical details via our product pages. Alternatively visit the Technical Downloads tab on the right of the page. If you have any problems or would rather receive the information by email please contact or call us on +44 (0)1953 423 423.

FAQ Index

© 2019 Sunfold Systems. Development by Netmatters Ltd.