Are bifold doors still popular?

Very, though the conversation has matured. Clients now choose bifolds deliberately where they want the whole opening cleared, and choose sliders where the view matters more than the aperture.

How many panels can I have?

Two to seven panels in most systems. Configuration matters more than count: a three-panel set folding one way behaves quite differently from a four-panel set splitting two and two.

Can they open internally or externally?

Both. External folding is the usual choice because it keeps the internal floor area clear, but internal folding suits covered terraces and tight external walkways.

Do bifolds keep the heat in?

Modern thermally broken aluminium bifolds achieve whole-door U-values from around 1.3 W/m²K with good double glazing. Weather seals and correct installation matter as much as the glass on a door used every day.

Are low thresholds available?

Yes, including a fully flush option with a drained channel beneath. It is worth confirming this early because it affects the floor build-up on both sides of the door.

Which aluminium systems do you recommend?

We specify a small number of systems we know perform in an exposed climate, chosen for roller quality, seal design and long-term hardware availability rather than headline price.

Are they suitable for large openings?

Yes, but panel weight rises quickly. Beyond roughly six metres we usually discuss whether a slider or a combination of slider and single door would work better day to day.

How much maintenance do they require?

Keep the bottom track clear of grit, wash the frames and lubricate the rollers and hinges annually. Neglected tracks are the single most common cause of bifold problems.

← Architectural Aluminium

Bifold Doors

Folding systems that open an elevation completely. Where a sliding door frames a view, a bifold removes the wall — the right choice for garden rooms, terraces and entertaining spaces.

Book A Design Consultation See It In Real Homes

5.0 from 7 Google reviews

Recent installations

Bifold Doors we have designed, surveyed and installed

Full-width glazed garden elevation with bifolding door, house near Penrith — Bifold Doors by Windows in the Lakes — Full-width glazed garden elevation with bifolding door, house near Penrith

Four-panel bifold run folded open onto a paved terrace, garden room near Keswick — Bifold Doors by Windows in the Lakes — Four-panel bifold run folded open onto a paved terrace, garden room near Keswick

Heritage Alunet bifold doors — Lancaster — Bifold Doors by Windows in the Lakes — Heritage Alunet bifold doors — Lancaster

Bifold installation — Lancaster — Bifold Doors by Windows in the Lakes — Bifold installation — Lancaster

Bifold doors wrapping a barn courtyard — Bifold Doors by Windows in the Lakes — Bifold doors wrapping a barn courtyard

Aluminium glazed run turning onto sandstone paving, brick courtyard range — Bifold Doors by Windows in the Lakes — Aluminium glazed run turning onto sandstone paving, brick courtyard range

Paired aluminium French doors between brick piers beneath oak lintels — Bifold Doors by Windows in the Lakes — Paired aluminium French doors between brick piers beneath oak lintels

Slim brown aluminium French doors set under a structural oak lintel — Bifold Doors by Windows in the Lakes — Slim brown aluminium French doors set under a structural oak lintel

Bifold doors opening onto a raised deck — Bifold Doors by Windows in the Lakes — Bifold doors opening onto a raised deck

Bifold doors to a clad garden room with fell views — Bifold Doors by Windows in the Lakes — Bifold doors to a clad garden room with fell views

Anthracite bifold doors to a brick garden extension — Bifold Doors by Windows in the Lakes — Anthracite bifold doors to a brick garden extension

Bifold doors seen from the living room, garden beyond — Bifold Doors by Windows in the Lakes — Bifold doors seen from the living room, garden beyond

Five-panel bifold doors to a rendered cottage extension — Bifold Doors by Windows in the Lakes — Five-panel bifold doors to a rendered cottage extension

Bifolds opening to garden terrace — Bifold Doors by Windows in the Lakes — Bifolds opening to garden terrace

A House Rebuilt Around Its Glazing — still from the project film

Watch Project Film1:03

See it in a real home

A House Rebuilt Around Its Glazing

A drone film over a whole-house remodel near Penrith — rising across the brick and render frontage, over the tiled hip and rooflight, then settling on the full-width glazed garden elevation.

Watch Project Film

A Garden Room Glazed on Three Sides — still from the project film

Watch Project Film0:37

See it in a real home

A Garden Room Glazed on Three Sides

A drone film over a brick garden room near Keswick — dropping from the rooftops onto the tiled gable and its rooflights, then working around two bifold runs folded open onto the terrace.

Watch Project Film

A Whole House, Front to Garden — still from the project film

Watch Project Film0:54

See it in a real home

A Whole House, Front to Garden

A drone film over a remodelled family house near Windermere — descending onto the render-and-brick front elevation and its bay windows, then rising over the ridge to the glazed garden room and lantern behind.

Watch Project Film

Courtyard Garden Room, Brick Barn-Style New Build — still from the project film

Watch Project Film0:11

See it in a real home

Courtyard Garden Room, Brick Barn-Style New Build

A tracking film along a brick courtyard range in South Lakeland — paired aluminium French doors, full-height fixed screens between brick piers and a bifolding return onto sandstone paving.

Watch Project Film

Why this system exists

The whole opening, open

Panels stack neatly to one or both sides, leaving over 90% of the aperture clear.

Slim stacked sightlines

Narrow mullions keep the closed elevation disciplined rather than busy.

Traffic door included

A single access leaf for everyday use, so the full set is only opened when you want it.

Weather-sealed properly

Multi-point locking, brush and bubble gaskets and drained thresholds detailed for exposed sites.

Bifold or sliding?

Bifolds win when you genuinely want the opening cleared — a terrace used daily in summer, a kitchen that becomes an outdoor room. Sliding doors win when the view matters more than the aperture, because the glass area is larger and the frame lines fewer.

We will recommend against a bifold where a slider serves the architecture better. That advice costs you nothing and saves regret.

Bifold Doors installed in a Cumbrian home

Considered detailing is what separates a fitted window from a finished one.

Recent installs

Recently completed across Cumbria and the North West

Real installations from across Cumbria and the North West — surveyed, specified and installed under our own supervision.

Alunet Aluminium Picture Windows, Eco Forest Lodges, installed in Ravenstonedale, 2026 — Alunet Aluminium Picture Windows, Eco Forest Lodges
Ravenstonedale · 2026

Alunet Aluminium French Door Sets, Eco Forest Lodges, installed in Ravenstonedale, 2026 — Alunet Aluminium French Door Sets, Eco Forest Lodges
Ravenstonedale · 2026

Glazed Rear Elevation, Heritage Aluminium Windows, installed in Near Penrith, 2025 — Glazed Rear Elevation, Heritage Aluminium Windows
Near Penrith · 2025

24 Heritage Aluminium Windows, Matt Black, installed in Near Penrith, 2025 — 24 Heritage Aluminium Windows, Matt Black
Near Penrith · 2025

Garden Room Glazed on Three Sides, Jet Black Bifolds, installed in Near Keswick, 2025 — Garden Room Glazed on Three Sides, Jet Black Bifolds
Near Keswick · 2025

Four-Panel Aluminium Bifold Run, installed in Near Keswick, 2025 — Four-Panel Aluminium Bifold Run
Near Keswick · 2025

Aluminium French Door Sets In Original Brick Arches, installed in Near Cartmel, 2025 — Aluminium French Door Sets In Original Brick Arches
Near Cartmel · 2025

Timber-Look uPVC Windows, Barn Conversion, installed in Near Cartmel, 2025 — Timber-Look uPVC Windows, Barn Conversion
Near Cartmel · 2025

Steel-Look Georgian-Bar Casements & Bay Windows, installed in Near Windermere, 2025 — Steel-Look Georgian-Bar Casements & Bay Windows
Near Windermere · 2025

Full-Width Garden Room Glazing & Lantern Rooflight, installed in Near Windermere, 2025 — Full-Width Garden Room Glazing & Lantern Rooflight
Near Windermere · 2025

Full-Width Slimline Sliding Doors, Clad Remodel, installed in North West, 2025 — Full-Width Slimline Sliding Doors, Clad Remodel
North West · 2025

Black Aluminium Picture Windows, Timber-Clad Elevation, installed in North West, 2025 — Black Aluminium Picture Windows, Timber-Clad Elevation
North West · 2025

32 Heritage Windows and 4 Doors, Stone Self Build, installed in West Yorkshire, 2025 — 32 Heritage Windows and 4 Doors, Stone Self Build
West Yorkshire · 2025

Black Heritage Windows with Georgian Bars, installed in West Yorkshire, 2025 — Black Heritage Windows with Georgian Bars
West Yorkshire · 2025

Triangular Gable Glazing and Heritage Casements, installed in West Yorkshire, 2025 — Triangular Gable Glazing and Heritage Casements
West Yorkshire · 2025

Steel-Look Doors and Screens, Barn Conversion, installed in North West, July 2026 — Steel-Look Doors and Screens, Barn Conversion
North West · July 2026

Flush Casement Windows, Oak-Framed Garden Room, installed in Cumbria, July 2026 — Flush Casement Windows, Oak-Framed Garden Room
Cumbria · July 2026

Grey Aluminium Windows and Doors, Full Elevation, installed in North West, July 2026 — Grey Aluminium Windows and Doors, Full Elevation
North West · July 2026

Steel-Look French Doors and Window Set, installed in North West, June 2026 — Steel-Look French Doors and Window Set
North West · June 2026

Anthracite Bifolding Doors, Brick Extension, installed in North West, July 2026 — Anthracite Bifolding Doors, Brick Extension
North West · July 2026

Steel-Look Screen and Doors, installed in North West, July 2026 — Steel-Look Screen and Doors
North West · July 2026

Three-Panel Slimline Sliding Doors, installed in North West, July 2026 — Three-Panel Slimline Sliding Doors
North West · July 2026

Five-Panel Bifolding Doors, Cottage Extension, installed in Cumbria, June 2026 — Five-Panel Bifolding Doors, Cottage Extension
Cumbria · June 2026

Steel-Look Doors and Matching Screen, installed in North West, June 2026 — Steel-Look Doors and Matching Screen
North West · June 2026

Slimline Sliding Doors, Brick Courtyard, installed in North West, June 2026 — Slimline Sliding Doors, Brick Courtyard
North West · June 2026

Full-Width Steel-Look Glazed Screen, installed in North West, June 2026 — Full-Width Steel-Look Glazed Screen
North West · June 2026

Heritage French Doors with Side Screens, installed in North West, May 2026 — Heritage French Doors with Side Screens
North West · May 2026

Aluminium Windows and Glazed Doors, installed in North West, May 2026 — Aluminium Windows and Glazed Doors
North West · May 2026

Bifolding Doors to a Barn Courtyard, installed in Cumbria, May 2026 — Bifolding Doors to a Barn Courtyard
Cumbria · May 2026

Gable-End Glazing and French Doors, installed in North West, May 2026 — Gable-End Glazing and French Doors
North West · May 2026

Internal Steel-Look Screen, installed in Cumbria, April 2026 — Internal Steel-Look Screen
Cumbria · April 2026

Bifolding Doors, Clad Garden Room, installed in Cumbria, April 2026 — Bifolding Doors, Clad Garden Room
Cumbria · April 2026

Aluminium Vertical Sliding Sash Windows, installed in Cumbria, March 2026 — Aluminium Vertical Sliding Sash Windows
Cumbria · March 2026

Slim 20mm Sliding Door Set, installed in Windermere, May 2026 — Slim 20mm Sliding Door Set
Windermere · May 2026

Heritage French Door Set, installed in Barrow, May 2026 — Heritage French Door Set
Barrow · May 2026

Single Door and Window, installed in Windermere, May 2026 — Single Door and Window
Windermere · May 2026

AB60 Smart French Doors, installed in Bowness, May 2026 — AB60 Smart French Doors
Bowness · May 2026

Heritage Alunet Bifold Doors, installed in Lancaster, May 2026 — Heritage Alunet Bifold Doors
Lancaster · May 2026

AS20 Smart Slimline Sliding Doors, installed in Carlisle, January 2026 — AS20 Smart Slimline Sliding Doors
Carlisle · January 2026

Farmhouse Extension Aluminium Windows, installed in Carlisle, January 2026 — Farmhouse Extension Aluminium Windows
Carlisle · January 2026

Full House Aluminium Windows, installed in Kirkby Stephen, August 2025 — Full House Aluminium Windows
Kirkby Stephen · August 2025

Technical

Specification at a glance

Final performance figures depend on configuration, glass make-up and installation detail. Full data sheets are issued with every quotation.

Systems: AB60 and heritage Alunet folding systems
Configurations: 2 to 7 panels, in-swing or out-swing, traffic door
Max panel: Up to 1.2m wide, 2.5m high
Thresholds: Flush or weathered
Finish: PPC RAL, dual colour
Guarantee: 10-year manufacturer backed

Choosing a system

AB-38 or AB-60 — how the two systems differ

Not all bifolds are the same door in a different colour. Frame strength, panel limits and thermal performance vary considerably between systems.

Alumil AB-38

Most slender · most glass

Currently the slimmest bifolding system in the UK, with an 88mm glass-to-glass sightline where panels meet. Specified where the visual impact of the opening is the point of the project.

— High-end extensions
— Contemporary new builds
— Minimal aluminium, maximum glass

Smart AB-60

Proven · serviceable

A refined version of one of Britain's most installed folding systems. Its adjustment mechanism allows the doors to be fine-tuned years later without removing the glass — a genuine advantage over a twenty-year life.

— Family homes
— Extensions and renovations
— Premium quality without extreme slimline

	Alumil AB-38	Smart AB-60
Position	Slimmest available	Balanced premium
Sightline where panels meet	88mm	120mm
Max panel width	1300mm	1200mm
Max panel height	3000mm	2500mm
Max sash weight	140kg	100kg
Glazing	Double (triple not required)	Double or triple
Double glazed U-value from	1.1 W/m²K	1.5 W/m²K
Triple glazed U-value from	Not required	1.2 W/m²K
Thresholds	Flush or low	Flush or weathered

Published U-values are based on standard test sizes. Installed performance varies with panel size, glass make-up, threshold and configuration.

Specify it your way

Colours, glass, hardware and details worth saving

Save anything that appeals and it travels with you — into your Inspiration Collection and then into your consultation.

Frame colours

RAL 7016 AnthraciteThe contemporary default — quiet against stone and render alike.
Pure White InteriorDual-colour frames that disappear from inside the room.
Jet BlackSteel-look elevations and rural conversions.
Painted CreamTraditional joinery language for cottages and farmhouses.

Glass & glazing

Corner pocket glazingTwo elevations opening into one another with no corner post.
Slim 20mm sliding sightlinesMaximum glass, minimum frame, panes that stack behind one another.
Full-height fixed panesFrameless-feeling picture glazing framing one specific view.

Hardware

Flush lever handlesMinimal, colour-matched and unobtrusive on modern frames.
Concealed hingesNothing interrupting the sightline when the frame is closed.
Monkey-tail handlesForged period detailing for heritage and conservation openings.

Design features

The whole opening, open
Panels stack neatly to one or both sides, leaving over 90% of the aperture clear.
Slim stacked sightlines
Narrow mullions keep the closed elevation disciplined rather than busy.
Traffic door included
A single access leaf for everyday use, so the full set is only opened when you want it.
Weather-sealed properly
Multi-point locking, brush and bubble gaskets and drained thresholds detailed for exposed sites.

How it is fitted — filmed on site

Fitting a Gable-End Apex Screen

Two installers set, pack and level a raked aluminium gable screen on a first-floor deck, then glaze the apex — filmed over a working morning.

0:32 · Windermere, Cumbria · August 2025

This is the part of a project homeowners rarely get to watch: a raked, gable-end aluminium screen being set into a finished opening at first-floor level. The frame is offered up dry, packed off the structure, checked for plumb and level, and only then fixed and glazed.

Everything about the sequence is deliberate. The deck is boarded and the working area kept to one side so the finished surfaces below are never used as a workbench. Packers carry the load at fixed points rather than the frame being pulled square with fixings. The apex angle is cut and jointed in the factory to the surveyed pitch, so nothing is adapted on site.

System: Smart aluminium, gable-end apex screen
Stage shown: Frame fitting through to sealing and finishing
Access: First-floor deck, boarded working zone
Frames: Powder-coated aluminium, raked to the roof pitch
Glazing: Double glazed units, externally glazed, internally beaded
Filmed: Windermere, Cumbria, August 2025

Frame fitting, packing and levellingGlazing the unitsAdjustment and alignmentWeather sealingTrims and finishing

The screen is offered up dry into the opening before a single fixing goes in — the check that everything the survey recorded is true on site.

Two installers work the frame together, packing it off the structure so the aluminium carries no twist from the building.

Plumb, level and diagonals are re-checked at the apex; the raked joint is factory cut to the surveyed pitch, never trimmed on the deck.

Glazing complete. A flat, even reflection across the panes is the quickest visual test that a frame has been fitted without distortion.

Cill and perimeter sealed, trims fitted and the deck cleared — the finishing stage that decides how the glazing performs for the next twenty years.

How it is fitted — filmed on site

Commissioning a Four-Panel Sliding Door Run

The moment a glazed, fifteen-metre sliding run is first moved on its track — the commissioning and adjustment stage, filmed on a garden room build near Grasmere.

0:17 · Near Grasmere, Cumbria · September 2025

This is the stage homeowners feel every single day for the next twenty years, and the one that separates a competent fit from a genuinely good one. The frames are in, the units are glazed, and the installer is now running each panel end to end by hand — repeatedly — to prove the track, the rollers and the interlocks before anything is signed off.

What you are watching is a test, not a demonstration. A correctly commissioned sliding panel moves with one hand, at the same effort from one end of the run to the other, and stops dead where you let go of it. Any change in resistance across the track means the cill is not perfectly level or the rollers need setting, and that is corrected now — while the building is still open and everything is accessible.

System: Slimline aluminium sliding doors, multi-panel run
Stage shown: Glazing through to commissioning, adjustment and handover
Setting: Single-storey garden room, timber frame, open to the field
Threshold: Low-level track set into the deck structure
Frames: Powder-coated anthracite grey aluminium
Filmed: Near Grasmere, Cumbria, September 2025

Glazing the unitsAdjustment and alignmentTrims and finishingClean down and handover

The full run, glazed and standing square, before commissioning begins — frames still masked and the working zone boarded out.

The track is set into the deck structure rather than sitting proud of it, so the finished floor can run level out to the terrace.

Each panel is run end to end by hand. Effort should stay identical across the whole track — a change in resistance means levels need adjusting.

Interlocks and stiles are checked closed: an even shadow gap top to bottom confirms the panel is hanging plumb on its rollers.

Commissioning complete. Flat, undistorted reflections across four large panes are the quickest visual test of a run fitted without twist.

Brochure

The Bifold Doors guide, including the mistakes worth avoiding

Configurations, sightline comparisons, structural considerations and the questions to ask before you order. Printed copies posted on request.

Download Our Brochure

Start the conversation

If you are planning an extension, renovation or new-build project and want glazing designed and installed without compromise, we would be glad to talk.