How wide can sliding doors be?

Individual panels can reach around 3 metres wide and 3.5 metres tall in the larger systems, with overall openings well beyond 8 metres when panels are combined. The practical limit is usually the structure above, not the door.

Can sliding doors be triple glazed?

Yes, though weight becomes the deciding factor. On large leaves we often recommend a high-performance double glazed unit with a warm-edge spacer and a solar-control coating, which performs superbly without adding several hundred kilograms.

What is the difference between lift-and-slide and inline sliders?

An inline slider runs on rollers permanently on the track. A lift-and-slide raises the panel clear of its seals as you turn the handle and drops it onto compression gaskets when closed, which makes very large panels easier to move and seals better against driving rain.

Are sliding doors secure?

Properly specified, yes. Multi-point locking, anti-lift blocks, laminated glass to accessible panes and hardware tested to PAS 24 are all standard on the systems we supply.

What threshold options are available?

Standard weathered thresholds, low thresholds and fully flush level thresholds. A flush detail needs drainage designed beneath the door, which is why it should be agreed before the slab is poured.

Can they be installed in extensions?

Most of the sliders we fit are in extensions. The important work happens early: the lintel or steel needs designing for deflection limits tighter than a standard opening, and the structural opening needs to be set out to the glazing dimensions.

Do they meet Building Regulations?

Yes. Thermal performance under Part L, safety glazing under Part K, and accessible threshold requirements are all addressed at specification stage, with certification issued on completion.

How much do premium sliding doors cost?

A three-metre two-panel set typically falls between £6,000 and £11,000 installed. Larger three-panel sets are usually £11,000 to £20,000, and slim-frame architectural systems begin around £18,000.

← Architectural Aluminium

Sliding Doors

Large-format sliding systems for openings where light, view and detailing matter. From 20mm interlocks to corner-pocket configurations where entire walls disappear into the structure.

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Recent installations

Sliding Doors we have designed, surveyed and installed

Rooflight over a fully glazed single-storey rear range, near Penrith — Sliding Doors by Windows in the Lakes — Rooflight over a fully glazed single-storey rear range, near Penrith

A garden room glazed on three elevations in jet black aluminium, near Keswick — Sliding Doors by Windows in the Lakes — A garden room glazed on three elevations in jet black aluminium, near Keswick

Slim sightlines and matching cills in RAL 9005 jet black — Sliding Doors by Windows in the Lakes — Slim sightlines and matching cills in RAL 9005 jet black

Full-width aluminium glazing to a brick garden room extension — Sliding Doors by Windows in the Lakes — Full-width aluminium glazing to a brick garden room extension

Lantern rooflight over a new kitchen, matched to the extension frames — Sliding Doors by Windows in the Lakes — Lantern rooflight over a new kitchen, matched to the extension frames

Full-width slimline sliding wall to a pool terrace, black frames throughout — Sliding Doors by Windows in the Lakes — Full-width slimline sliding wall to a pool terrace, black frames throughout

Open sliding wall seen from the kitchen, terrace and pool beyond — Sliding Doors by Windows in the Lakes — Open sliding wall seen from the kitchen, terrace and pool beyond

Slimline slider aligned beneath a black canopy in low evening sun — Sliding Doors by Windows in the Lakes — Slimline slider aligned beneath a black canopy in low evening sun

Aerial view of a whole-house glazing package and full-width slider — Sliding Doors by Windows in the Lakes — Aerial view of a whole-house glazing package and full-width slider

Slimline sliding doors opening to the fells — Sliding Doors by Windows in the Lakes — Slimline sliding doors opening to the fells

AS20 Smart slimline sliding doors — Carlisle — Sliding Doors by Windows in the Lakes — AS20 Smart slimline sliding doors — Carlisle

Slimline sliding doors to a brick courtyard elevation — Sliding Doors by Windows in the Lakes — Slimline sliding doors to a brick courtyard elevation

Visualisation: sliding doors and roof lantern to a rear extension — Sliding Doors by Windows in the Lakes — Visualisation: sliding doors and roof lantern to a rear extension

Visualisation: three-panel slimline slider across a rear elevation — Sliding Doors by Windows in the Lakes — Visualisation: three-panel slimline slider across a rear elevation

Visualisation: slimline sliding doors open to a terrace — Sliding Doors by Windows in the Lakes — Visualisation: slimline sliding doors open to a terrace

Visualisation: slim interlock and threshold detail — Sliding Doors by Windows in the Lakes — Visualisation: slim interlock and threshold detail

Three-panel slimline slider in a brick opening — Sliding Doors by Windows in the Lakes — Three-panel slimline slider in a brick opening

Corner-pocket sliding door, glass extension — Sliding Doors by Windows in the Lakes — Corner-pocket sliding door, glass extension

Ultraline slim sliding corner door — Sliding Doors by Windows in the Lakes — Ultraline slim sliding corner door

Whole-House Aluminium Glazing, Contemporary Clad Remodel — still from the project film

Watch Project Film0:42

See it in a real home

Whole-House Aluminium Glazing, Contemporary Clad Remodel

A drone film of a full-house aluminium glazing package — slimline sliding doors, square picture windows and black frames throughout, over a timber-clad remodel and pool terrace.

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

Why this system exists

Maximum glass

Interlocks from 20mm and panels weighing up to 400kg, engineered so the frame reads as a line rather than a barrier.

Corner pocket configurations

Cortizo systems allow panels to retract fully into concealed wall pockets — no post, no frame, no interruption between inside and out.

Effortless operation

Precision track alignment and stainless running gear mean a door of two metres moves with one hand, year after year.

Engineered early

We work with architects, builders and structural engineers before steelwork is finalised, so the opening is right the first time.

Choosing the right sliding system

There is no single best aluminium sliding door. The right system depends on overall opening width and height, desired sightlines, panel weight, exposure and how the doors will be used day to day.

Our role is to assess these factors during the survey stage and recommend the system that suits your home and project — rather than forcing a pre-selected option.

Corner pocket sliding doors

Corner pocket sliding doors create one of the most striking architectural features available in modern glazing. Because they interact directly with the building structure, early coordination is critical: track alignment, panel weight, pocket construction, drainage and structural support must all be resolved before construction progresses.

If you are considering a corner opening as part of a new build, extension or high-end renovation, discuss the glazing before final drawings are signed off.

Sliding 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: Slimline 20mm, Cor Vision, corner pocket (Cortizo)
Max panel: Up to 3.5m high, up to 400kg per leaf
Interlock: From 20mm
Thresholds: Flush, weathered and low-rise options
Glazing: Double or triple, solar control and acoustic options
Guarantee: 10-year manufacturer backed

Choosing a system

Cor Vision or AS-20 — the honest comparison

Two slimline systems, both with 20mm interlock sightlines, separated by structural ambition and budget. This is how they differ in practice.

Cortizo Cor Vision

Minimal frame · design-led

Frames can be concealed into the surrounding structure so the glass reads almost edge to edge. It demands coordination with the builder and is best specified as part of a wider build rather than a straight replacement.

— Design-led barn conversions
— High-end extensions
— Corner and pocket openings

Smart AS-20

Slimline · everyday premium

Slim sightlines and strong thermal figures without the structural demands of an ultra-premium system. The system we specify most often where modern glazing is being introduced into a traditional Cumbrian building.

— Stone cottages
— Period renovations
— Medium-scale extensions

	Cortizo Cor Vision	Smart AS-20
Position	High-end, design-led	Balanced premium
Interlock sightline	20mm	20mm
Max sash width	2500mm	2200mm
Max sash height	3000mm	2500mm
Max sash weight	320kg	250kg
Glazing	Double or triple	Double or triple
Double glazed U-value from	1.6 W/m²K	1.4 W/m²K
Triple glazed U-value from	1.3 W/m²K	1.3 W/m²K
Pocket option	Yes, including corners	Limited
Thresholds	Flush or ultra-low	Low or standard

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

Slim 20mm sliding sightlinesMaximum glass, minimum frame, panes that stack behind one another.
Corner pocket glazingTwo elevations opening into one another with no corner post.
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.
Brushed bronze ironmongeryWarm metal against dark frames — the detail people touch.

Design features

Maximum glass
Interlocks from 20mm and panels weighing up to 400kg, engineered so the frame reads as a line rather than a barrier.
Corner pocket configurations
Cortizo systems allow panels to retract fully into concealed wall pockets — no post, no frame, no interruption between inside and out.
Effortless operation
Precision track alignment and stainless running gear mean a door of two metres moves with one hand, year after year.
Engineered early
We work with architects, builders and structural engineers before steelwork is finalised, so the opening is right the first time.

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 Sliding 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.