Flagship guide · 9 min read
The Ultimate Guide to Sliding Doors
How aluminium sliding doors work, what separates a good system from a poor one, and what to expect from specification through to installed cost.
← 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.
5.0 from 7 Google reviewsAre slimline sliding doors suitable for exposed locations?
Often yes, but the specification has to be chosen for the exposure rather than for the sightline alone. On an exposed site the things that matter are the system's tested wind and watertightness ratings, threshold and drainage detailing, panel size and weight, gasket quality and the installation detail around the opening. A slim interlock is achievable on an exposed elevation, but the panel sizes and threshold type that go with it are decided against the site. Final suitability depends on the chosen system, dimensions, glazing and configuration.
From a real Windows in the Lakes project
Brampton, Carlisle · 5600mm × 2100mm AS-20 slider · 6 windows
Slimline Sliding Doors, Barn Conversion near Brampton
The rural location brought access challenges typical of farm conversions — restricted access and limited working space for deliveries and installation — alongside the irregular geometry of the original structure.
We coordinated closely with the wider build team on scheduling to minimise disruption, and carried out a full professional survey with every opening measured and checked in detail before manufacture. Installation focused on structural interfaces, weather tightness and clean internal and external detailing.
Read the project storyRecent installations
Sliding Doors we have designed, surveyed and installed
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.
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.
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.
Why this system exists
01
Maximum glass
Interlocks from 20mm and panels weighing up to 400kg, engineered so the frame reads as a line rather than a barrier.
02
Corner pocket configurations
Cortizo systems allow panels to retract fully into concealed wall pockets — no post, no frame, no interruption between inside and out.
03
Effortless operation
Precision track alignment and stainless running gear mean a door of two metres moves with one hand, year after year.
04
Engineered early
We work with architects, builders and structural engineers before steelwork is finalised, so the opening is right the first time.
Suitability
Where sliding doors belong, and where they do not
Best suited to
- Wide openings where an uninterrupted view when closed is the priority
- Everyday garden access rather than occasional full-width opening
- Rooms where a flush or low threshold and level transition are wanted
- Elevations where minimal interlocks make the glazing read as one plane
Less suitable when
- Openings that need to be fully clear across their whole width
- Narrow openings where a sliding panel gives little usable clear width
- Projects with no allowance for the structural support large panels require
- Sites where the threshold and drainage detail cannot be resolved properly
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 consultation, recommend the system that suits your home and project, then confirm the final details at the post-order survey — 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.
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
Ravenstonedale · 2026
Alunet Aluminium French Door Sets, Eco Forest Lodges
Ravenstonedale · 2026
Glazed Rear Elevation, Heritage Aluminium Windows
Near Penrith · 2025
24 Heritage Aluminium Windows, Matt Black
Near Penrith · 2025
Garden Room Glazed on Three Sides, Jet Black Bifolds
Near Keswick · 2025
Four-Panel Aluminium Bifold Run
Near Keswick · 2025
Aluminium French Door Sets In Original Brick Arches
Near Cartmel · 2025
Timber-Look uPVC Windows, Barn Conversion
Near Cartmel · 2025
Steel-Look Georgian-Bar Casements & Bay Windows
Near Windermere · 2025
Full-Width Garden Room Glazing & Lantern Rooflight
Near Windermere · 2025
Full-Width Slimline Sliding Doors, Clad Remodel
North West · 2025
Black Aluminium Picture Windows, Timber-Clad Elevation
North West · 2025
32 Heritage Windows and 4 Doors, Stone Self Build
West Yorkshire · 2025
Black Heritage Windows with Georgian Bars
West Yorkshire · 2025
Triangular Gable Glazing and Heritage Casements
West Yorkshire · 2025
Steel-Look Doors and Screens, Barn Conversion
North West · July 2026
Flush Casement Windows, Oak-Framed Garden Room
Cumbria · July 2026
Grey Aluminium Windows and Doors, Full Elevation
North West · July 2026
Steel-Look French Doors and Window Set
North West · June 2026
Anthracite Bifolding Doors, Brick Extension
North West · July 2026
Steel-Look Screen and Doors
North West · July 2026
Three-Panel Slimline Sliding Doors
North West · July 2026
Five-Panel Bifolding Doors, Cottage Extension
Cumbria · June 2026
Steel-Look Doors and Matching Screen
North West · June 2026
Slimline Sliding Doors, Brick Courtyard
North West · June 2026
Full-Width Steel-Look Glazed Screen
North West · June 2026
Heritage French Doors with Side Screens
North West · May 2026
Aluminium Windows and Glazed Doors
North West · May 2026
Bifolding Doors to a Barn Courtyard
Cumbria · May 2026
Gable-End Glazing and French Doors
North West · May 2026
Internal Steel-Look Screen
Cumbria · April 2026
Bifolding Doors, Clad Garden Room
Cumbria · April 2026
Aluminium Vertical Sliding Sash Windows
Cumbria · March 2026
Slim 20mm Sliding Door Set
Windermere · May 2026
Heritage French Door Set
Barrow · May 2026
Single Door and Window
Windermere · May 2026
AB60 Smart French Doors
Bowness · May 2026
Heritage Alunet Bifold Doors
Lancaster · May 2026
AS20 Smart Slimline Sliding Doors
Carlisle · January 2026
Farmhouse Extension Aluminium Windows
Carlisle · January 2026
Full House Aluminium Windows
Kirkby Stephen · August 2025
Technical
Specification at a glance
Figures shown are indicative system capabilities. Final performance depends on the chosen system, dimensions, glass make-up, configuration and installation detail, and is confirmed on the manufacturer data sheets issued with every quotation. Guarantee cover varies by product and component. The applicable frame, glazing, hardware and installation guarantees are set out in writing at quotation stage.
- 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
- Guarantees
- Confirmed by product and component with quotation
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
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
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.
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.
Direct
01768 254554projects@windowsinthelakes.co.ukBased in Appleby-in-Westmorland, with installation teams across Penrith, Keswick, Kendal, Windermere and the South Lakes.
Common questions
Sliding Doors: your questions answered
Practical answers to what homeowners ask us most about this system. Anything else, just ask.
Book a Design ConsultationVisit the Knowledge CentreKnowledge Centre
Guides worth reading first
Flagship guide · 6 min read
The Best Windows for a Barn Conversion
A barn conversion is not a window replacement job. It is a small number of large, unrepeatable glazing decisions, and the material and detailing you choose will define how the finished building reads.
Flagship guide · 8 min read
Choosing Windows for a Lake District Property
Lake District houses ask more of their glazing than most. This is how we specify windows and doors for stone cottages, farmhouses, renovations, extensions and contemporary homes across Cumbria.
Get an initial project price
Planning a large sliding-door opening?
Send us the approximate opening size, drawings or photographs and we’ll help you understand the likely system and investment required.
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Wondering what this collection typically costs?
Plan your project investment with a guide based on comparable completed projects.
Designed with
Frequently paired with this collection.
RAL 7016 Anthracite GreyColours Studio
Solar Control GlassGlass Studio
Brushed Bronze Pull BarHardware Studio
Flush ThresholdsDesign Details
Obscure Glass CollectionGlass StudioDual Colour: Anthracite / WhiteColours Studio
Design Studio
Keep exploring in the Design Studio
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Let’s design something exceptional.
Bring us your drawings, your site photographs or simply an idea. We will tell you what is possible, what it should cost and how long it will take.