Two panels, one sliding
The simplest and most economical layout. One fixed panel, one that slides behind it.
Aluminium · Inline sliding
As little frame as the glass allows.
Slim sliding doors run on rollers in a bottom track, with a narrow interlock where the panels meet. With no lift mechanism, the hardware is simpler, the frames slimmer and the cost lower. For moderate panel sizes, it's the cleanest way to put a wall of glass in a London extension.
- Panel weightup to 250 kg
- Panel heightup to 3,000 mm
- Panel widthup to 2,800 mm
- Interlock sightlinefrom c. 35 mm
- Thresholdflush or ≤15 mm
- Whole-door Uwfrom c. 1.0 W/m²K
Indicative System-class envelope. Certified values are published with each system data sheet.
Choosing a system
When slim sliding is the right call
Slim sliding and lift & slide look similar from the garden. The difference is in the hardware and the seal. Choose by panel weight, exposure and budget. Our full three-way comparison includes bi-folds.
Choose slim sliding when…
- Panels stay under about 250 kg (roughly 2.5 m² of triple glazing).
- The look matters most: the slimmest interlocks and frames.
- The site is sheltered, like most rear gardens and side returns.
- Budget matters. The hardware is simpler than lift & slide.
Choose lift & slide instead when…
- Panels are very large or heavy (up to 400 kg).
- The site is exposed or noisy, and compressed gaskets seal better than brushes.
- You need the best airtightness for a Passivhaus-style or low-energy build.
How it works
Rollers, a track and a well-made interlock.
Rollers in the bottom track
Each sliding panel sits on twin stainless-steel rollers, sized to its weight. The track can sit flush with the floor.
Seals at every joint
Brush seals and gaskets close the gaps at the interlock, head and sill. Multi-point locks pull the panels tight when you lock them.
Push to slide
No handle to turn first: unlock and slide. Soft-close and motorised options are available on larger panels.
Configurations
Six layouts for slim sliders
Plan views. Accent lines are sliding panels; grey lines are fixed.
Two panels, both sliding
Either panel opens, so you can choose which side to walk through or open both halves for air.
Three panels, three tracks
Two panels stack behind one fixed panel and two-thirds of the width opens. Good for side returns.
Four panels, centre opening
A symmetrical garden elevation that keeps each panel inside the inline weight range.
Corner, no post
Two sliders meet at a corner with no post. The corner load goes into the structure, so engineer it at Stage 3.
The panels disappear into the wall for a full-width opening. The wall cavity has to be designed for it.
Sizing tool
Will slim sliding carry it?
Enter the structural opening. The tool checks panel weight against the inline hardware range and tells you when lift & slide is the safer choice. These are planning figures only.
- Panel width
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- Approx. panel weight
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- Approx. clear opening
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- Opening area
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Performance
Design envelope
Ranges for an inline sliding system of this class. On each project we issue the certified values for your sizes and glass.
Indicative We'll replace each range with the certified value and its test reference once the system data sheet is published.
| Thermal transmittance, whole door (Uw) | c. 1.0–1.6 W/m²KTriple vs double glazing and size. Approved Document L limiting values: 1.4 for replacement doors in existing homes; 1.6 in new dwellings. |
|---|---|
| Maximum panel weight | up to c. 250 kgSet by the roller class. |
| Maximum panel size | c. 2,800 × 3,000 mm |
| Interlock sightline | from c. 35 mmSlim interlock option. |
| Threshold | Flush (recessed) or low upstand ≤15 mmMeets the accessible-threshold expectation in Approved Document M. |
| Security | Specified to PAS 24:2022Needed for doors in new dwellings under Approved Document Q. |
| Weather (BS 6375-1 / EN 12207, 12208, 12210) | Classified per system test reportBrush-sealed systems suit sheltered sites best. |
| Acoustic (Rw) | up to c. 36 dBWith laminated acoustic glass. |
| Safety glazing | Toughened or laminated throughoutDoors are critical locations under Approved Document K. |
Thresholds & tracks
A track you don't trip over, and water that goes somewhere.
A recessed track gives a level floor from inside to out. It has the same three requirements as any flush threshold.
- A slab recess to the depth the system needs, given at Stage 3.
- A continuous thermal line under the frame.
- A linear drain outside, with paving that falls away from the door.
- Keep the track clear. Fine gravel and leaves are the enemy of every slider.
Glass, finish, hardware
Specified once, built as drawn.
Glass
Double or triple
Low-E, warm edge, argon. Solar control for south and west elevations, and acoustic laminated glass near roads.
Finish
Any RAL, dual colour
Architectural powder coat or anodised, matched across every system in the house.
Hardware
Slim handles, multi-point locks
Flush pulls inside, optional key locking outside, and soft-close on larger panels.
Designing in London
What to get right on a slim slider
The same four checks as any large opening. Our design guide explains each one.
01 · Structure
Head deflection
Slim frames hide less movement. Design the beam to the system limit and detail a deflection gap.
02 · Exposure
Know the site
Brush seals are fine in a sheltered garden. Upper floors, roof terraces and open sites may need lift & slide.
03 · Access
Panel route
Lighter than lift & slide, but a 2.5 m panel still has to get through the house. We check the route at survey.
04 · Regulations
Part L, K, M, Q
Uw against the limiting value, the 25% glazing rule for extensions, safety glass, Part M thresholds and PAS 24.
Technical files
Slim sliding spec pack
We'll publish it when the system data sheet is certified. Until then, request it and we'll send the current drafts for your project.
| File | Format | Status |
|---|---|---|
| Head, sill, jamb & interlock details | DWG · PDF | Preparing |
| Flush & low threshold details | DWG · PDF | Preparing |
| BIM object | RVT · IFC | Preparing |
| NBS-style specification clause | DOCX | Preparing |
| Data sheet & declaration of performance | Preparing |
Questions
Slim sliding FAQ
What's the difference between slim sliding and lift & slide?
Lift & slide panels are lifted onto rollers by the handle and lowered onto gaskets to seal. That carries heavier panels and seals better. Slim sliders roll all the time and seal with brushes and gaskets. They're lighter, slimmer and cheaper, and best for moderate panel sizes on sheltered sites.
How slim is “slim”?
Interlocks from around 35 mm on this class of system. Some minimal systems go further by hiding the outer frame in the floor, walls and ceiling. That needs more building work, so decide at Stage 2.
Will it be draughty?
A well-made slider with multi-point locking is weathertight on a typical London rear elevation. On exposed sites, upper floors or roof terraces, we'll tell you if lift & slide is the better choice.
Can it have a flush threshold?
Yes. The track recesses into the floor, with a linear drain outside. The slab has to be designed for it before it's poured.
Is it secure?
We specify to PAS 24:2022 with multi-point locking and laminated glass where needed, which is the standard for new dwellings under Part Q.
Who makes and installs it?
We make it to order on a branded system and install it with our own team, with one project manager from survey to handover.