Slim-Framed Aluminium Bi-Fold Doors for Seamless Indoor and Outdoor Living
Bi-folding doors began as space-saving internal doors, but they have become a favourite for garden rooms and extensions. Floor to ceiling glass creates a seamless link between inside and out, and because the panels fold flat to the side instead of sliding behind each other, you open far more of the aperture than with a standard sliding door.
Eurothermal's aluminium bi-fold doors are made to measure in sizes from a compact 1.4m with two panels up to a generous 6.2m with seven, with slim frames, strong locking and double or triple glazing. Our FENSA certified team fits them with a full product and installation guarantee, across Hayes, Hillingdon, Uxbridge, Southall and Yeading.
Opening and layout
- Panels fold flat to the side to open far more of the aperture than a slider
- Sizes from 1.4m with two panels up to 6.2m with seven suit every opening
- Choose left, right or split stacking to fit your room and your garden
- A traffic door lets you step out without folding the whole set back
Strength and comfort
- Slim thermally broken aluminium frames carry large panes of glass with minimal frame
- Multipoint locking and shootbolts hold every panel securely when the doors are closed
- Double or triple glazing with up to A++ ratings keeps heat in
- Powder coated finishes in a wide colour range never need painting
01 / Doors
How Many Panels Do You Need?
The number of panels follows the width of your opening, and it is the biggest driver of price. This is how the common layouts compare.
| Panels | Typical opening width | Suits | Typical supplied and fitted price (UK guides, 2026) |
|---|---|---|---|
| 2 panels | About 1.4m to 2m | A narrow doorway or small kitchen | Roughly £2,000 to £3,600 |
| 3 panels | About 2.4m to 3m | A standard rear opening | Roughly £3,000 to £5,000 |
| 4 panels | About 3m to 4m | A wider kitchen diner | Roughly £3,800 to £6,500 |
| 5 panels | About 4m to 5m | Large extensions | Roughly £4,600 to £8,500 |
| 6 to 7 panels | Up to 6.2m | Very wide openings | Roughly £6,000 to £12,000 |
Prices are independent UK guide ranges, not a Eurothermal quote, and they exclude structural work to create or widen the opening.
02 / Doors
Which Way Will the Doors Stack?
When open, the folded panels stack to one side or split to both. Planning this early avoids surprises.
- Stack left or stack right, so the panels gather neatly at one side of the opening
- Split stack, with panels folding to both sides, which suits a wide, central opening
- Leave clear space inside for the folded stack, and keep furniture and radiators away from it
- Most bi-folds open outwards, which keeps the room clear, though inward opening is possible where the garden side is restricted
03 / Doors
What Is a Traffic Door?
A traffic door is a single panel within the bi-fold set that opens like an ordinary door. It means you can step in and out for everyday use without folding back the whole system, which saves effort and keeps heat in when you only need quick access.
- Choose which panel is the traffic door, usually at one end
- Keep the whole set closed on cold days and use the traffic door for daily access
- Open every panel together when you want the full width for summer
04 / Doors
Flush, Low or Standard Threshold?
The threshold is the strip along the floor where the doors meet the ground. It decides how smooth the transition is, and how well water drains away.
- A flush or low threshold gives a step-free, seamless link to the patio and suits wheelchairs and pushchairs
- It needs careful drainage planning at the base, so it usually adds a modest cost, roughly £100 to £300
- A standard raised threshold is the simplest and most weathertight, with a small step
- We measure your floor and patio levels at survey and recommend the right option for your garden
05 / Doors
Is Your Opening Ready? A Pre-Order Checklist
Bi-folds are heavier than most doors, so the opening matters.
- Measure the existing opening, and note if you are replacing doors, converting a window or creating a new opening
- For a new or widened opening, a structural lintel is needed, and this is the main extra cost
- Building Regulations apply to new or widened openings, and building control fees are typically a few hundred pounds
- Replacing existing doors in the same opening is usually permitted development, but listed buildings and conservation areas can differ
- Check floor and patio levels so the threshold and drainage work
- A FENSA or CERTASS registered installer certifies the work for Building Regulations, and we confirm what applies at your free survey
06 / Doors
Light, Heat and Glare: Choosing the Glass
A wall of glass brings light, and it also brings summer heat and winter heat loss. Choose the glass for the way you live.
- Double or triple glazing, with up to A++ ratings, keeps heat in during winter
- Solar control glass reduces summer overheating on a south facing garden
- Triple glazing adds warmth and sound reduction near busy roads or flight paths
- Integral blinds between the panes add privacy and shade without curtains
- Toughened or laminated glass adds safety and impact resistance
07 / Doors
Security and Weather: Honest Answers
Bi-folds have more panels and joints than a sliding door, so the quality of the seals, drainage and locking really matters.
- Multipoint locking and shootbolts secure the panels, and key locking handles prevent opening from outside
- A quality system uses overlapping seals and drainage channels to keep out wind and rain
- We tell you at survey if the position of your doors, such as an exposed elevation, needs extra care
- Keep the bottom track clear of debris and the hinges lubricated, so the doors fold smoothly
08 / Doors
Bi-Fold, Sliding or French Doors: Which Opens What You Want?
- Choose bi-fold doors if you want to open almost the whole width and create a seamless indoor and outdoor space
- Choose sliding doors if you want a simpler, lower cost door and need no space for a stack or a swing. A standard slider opens only about half the aperture, see our uPVC Patio and Sliding Patio pages
- Choose French doors if you want a traditional hinged opening at a lower cost, see our uPVC French page
09 / Doors
Bi-Fold Doors for Hayes Extensions and Garden Rooms
Many Hayes houses have a rear garden that is long and narrow, and bi-folds are one of the best ways to open a kitchen diner or side return extension to it. They suit new extensions, garden rooms and conversions, and they work particularly well with a matching aluminium window, roof lantern or skylight above.
How It Works
From your first enquiry to installation and aftercare, we keep each stage clear and straightforward.
About Us-
1
Tell Us About Your Project
Tell us what you want to replace or install and where the property is located.
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2
Technical Survey
Where required, we measure the openings and assess the practical requirements of your property.
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3
Confirm Your Specification
Choose the frame material, glazing, opening style, colours, finishes and hardware.
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4
Made to Measure
Your selected windows or doors are produced to the agreed dimensions and specification.
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5
Installation & Aftercare
Our team completes the installation, checks the finished system and remains available for aftercare.
Frequently Asked Questions
Ask Us a QuestionWhat is a traffic door on a bifold door?
A traffic door is a single panel within the bi-fold set that opens independently like a normal door. It lets you step in and out for everyday use without folding back the whole system. You choose which panel it is when the doors are made.
How wide can bi-fold doors be?
Our aluminium bi-fold doors are made to measure from 1.4m wide with two panels up to 6.2m wide with seven panels. The width of your opening decides how many panels you need, and we recommend the layout at your survey.
Which side do bifold doors stack on?
You choose left, right or a split stack, where panels fold to both sides. Pick the side that keeps the stack clear of furniture, radiators and the route you walk, and leave room inside for the folded panels.
Are bifold doors draughty or do they leak?
A well made, properly installed bi-fold is weathertight, but they have more joints than a sliding door, so the quality of the seals and drainage matters. Problems usually come from cheap systems, poor installation or a dirty bottom track, not from bi-folds as a design.
Are bi-fold doors secure?
Yes, when they are specified properly. Multipoint locking, shootbolts and key locking handles secure the panels, and toughened or laminated glass adds strength. Ask for the exact security specification of the set you are quoted.
Do I need planning permission or Building Regulations for bifold doors?
Replacing existing doors in the same opening is usually permitted development and does not need planning permission, though listed buildings and conservation areas can differ. Creating or widening an opening needs a structural lintel and Building Regulations approval. A FENSA or CERTASS registered installer certifies the glazing work, and we advise at survey.
How much do aluminium bifold doors cost?
Independent UK guides put aluminium bi-fold doors at roughly £3,000 to £7,500 supplied and fitted for typical sets, from about £2,000 for a small two panel set up to £8,500 or more for five panels or more. Structural work, building control, a flush threshold and large glazing add to the price. These are national guide figures, not a Eurothermal quote, so book a free survey for an exact price.
Can I have a flush threshold on bi-fold doors?
Yes, a flush or low threshold gives a step-free, seamless link between inside and out. It needs careful drainage and usually adds a modest cost of roughly £100 to £300, so we check your floor and patio levels at survey.
Are bi-fold doors better than sliding doors?
They open more of the aperture, because the panels fold flat to the side rather than only half the width, and they create a bigger indoor and outdoor space. Sliding doors cost less and need no space to stack or swing. Choose the one that matches how much opening you want.
How do I look after bi-fold doors?
Keep the bottom track clear of leaves and grit, wipe the frames and glass with warm soapy water, and lubricate the hinges and running gear once or twice a year with a suitable lubricant. Check that drainage channels are clear and that every panel folds and locks smoothly.