A four panel sliding door is the usual reply to a wide wall that an owner wants to open to the garden. The label, though, tells you how many leaves the wall is divided into — not how much of that wall actually becomes a clear opening when the door is parked open. The two numbers are not the same, and on a large span the difference is exactly what decides whether the project works.
This article works from the geometry of four-leaf sliding systems and from the real published specifications of the ALPES sliding range, then states plainly where the buildable limit sits. No prices, no performance ratings, and no warranty years are quoted — those are project-specific and must be confirmed in writing with the factory.
Read a four-panel door left-to-right from outside and it is a sequence of fixed (O) and sliding (X) leaves. The clear opening you get is set by how many leaves slide and where they park, not by the total count:
| Arrangement | What moves | Clear opening when parked | Needs wall depth to park? |
|---|---|---|---|
| OXXO (fixed–slide–slide–fixed) | Two centre leaves slide outward to the ends | Two leaf widths of four — about one-half | No, leaves park inside the frame |
| XOOX (slide–fixed–fixed–slide) | Two end leaves slide inward to meet at centre | Two leaf widths of four — about one-half | No, leaves park inside the frame |
| All-four stacking (e.g. XXXX) | Every leaf slides and stacks at one or both ends | Up to about three-quarters to nine-tenths; one leaf width stays at the stack | Yes — each parked leaf needs its frame depth beside the opening |
The honest line: a standard four-panel OXXO opens only about one-half of its width — the same fraction as a plain two-panel OX door. The "large opening" promise only shows up in a stacking layout, and stacking costs wall space. Compared with a triple sliding door in a three-track layout (about two-thirds open), the four-panel fixed-end design is not automatically more open. It is wider, not more open.
A sliding door spans a wall by adding leaf widths. Four leaves let you keep each leaf inside its weight limit while covering a wide total — instead of one oversized leaf that no roller system can carry. The ALPES sliding range gives three published series you can build a four-panel wall from:
| Series | Profile | Frame wall width | Single-leaf max size | Roller rating |
|---|---|---|---|---|
| SL155 thermal-break | 6060-T66, 2.2–2.5 mm, four-track | 155 mm (four track) | 2800 mm W × 2600 mm H, about 7.5 m² daylight | 20-wheel self-balancing, 400 kg |
| SL126 / 182 (96) | 6060-T66, 2.0 mm (3.0 mm reinforced) | 126 mm (two track) / 182 mm (three track) | 2500 mm W × 3000 mm H, about 7 m² daylight | Lift-sliding; 27A inert-gas glazing |
| SL112 / 167 heavy-duty | 6060-T66, 1.8–2.5 mm | 112 mm (two track) / 167 mm (three track) | 24A insulated glass, up to 220 kg drive | 45 mm high-ｄｒｏｐ track + 85 mm barrier |
On a sliding door patio wall, four SL155 leaves at the published 2800 mm width reach a total span near 11200 mm before you even consider stacking — far wider than any two-leaf door could carry on one roller set. The four-leaf count is what makes that span buildable.
Every leaf is carried by its roller rating. A widely used industry rule of thumb puts glass near 2.5 kg per square metre per millimetre of thickness. The arithmetic below is our own, for illustration only — not an ALPES published value. Verify the max leaf width with the factory for your exact glass build-up.
| Assumed glazing | Approx. glass weight at 2.8 m × 2.6 m | Within SL155 400 kg? |
|---|---|---|
| 6 + 24A + 6 (about 30 mm total) | about 182 kg | Yes, with margin |
| 8 + 1.52 PVB + 8 laminated (about 40 mm total) | about 290 kg | Yes, but less margin |
The takeaway: the published max leaf size is stated for an assumed glass thickness. Specify heavier glass and the max leaf width comes down, which in turn caps the total span four leaves can cover. Weight, not the number four, is the wall's true limit.
It is easy to assume more rails means a deeper frame. The ALPES numbers disprove that: the four-track SL155 is 155 mm deep, while the three-track SL126 / 182 is 182 mm deep. The deeper frame belongs to the series with fewer rails. Frame depth is a property of the series profile, not of how many rails it carries — so a four-panel wall can be shallower in the wall than a three-panel wall from a different series.
This matters at the rough opening: the frame must sit inside the wall build-up, and the wall thickness (not the leaf count) decides which series fits. Send the wall lay-up from outside to inside, not just one depth number.
A wide sliding wall hangs its whole glass weight from the head track and the lintel above it. Two structural facts decide whether the door slides true for its whole life:
A sliding leaf seals by contact at the meeting stiles — brush pile plus a weather strip — not by full-perimeter compression the way a casement does. The SL126 / 182 lift-slide improves this: turning the handle lifts the leaf off the bottom seal for near-frictionless travel, then drops it onto compressive seals when closed. That is the strongest seal a sliding system gives you.
ALPES publishes whole-unit K values only for the tilt-turn and casement lines (about 1.3 for AW90, 1.6 for C120, 1.7 for C116). The sliding series — SL155, SL126 / 182, SL112 / 167, and the TS130 side-press window — publish no whole-unit thermal value. Ask for a calculated value against your exact glazing build-up rather than reading a number meant for a different product.
Plan the parked position before the wall is built. A one-way stack puts all moving leaves at one end; a bi-parting stack splits them to both ends for symmetry but needs clear space on both sides. Neither ALPES sliding series offers a pocket (wall-cavity) option, so a fixed-end four-panel door always leaves at least one leaf width in view when open. If the brief demands the wall to vanish completely, say so now — stacking reaches about three-quarters to nine-tenths open, not fully clear, without a cavity.
| Situation | Why a four-panel slider struggles | Better path |
|---|---|---|
| Small room | Four leaves dominate the wall and the parked stack eats floor | Two-panel or a fixed-plus-one layout |
| Full compression seal needed | Sliding seals by contact, not perimeter compression | Tilt-turn or casement line |
| Wall must vanish fully | No pocket option; stacking leaves one leaf width in view | Pocket system, or accept three-quarters open |
| Item | ALPES publishes | You must request |
|---|---|---|
| Profile, alloy, wall thickness | 6060-T66, 1.8–2.5 mm | Reinforced zones for your span |
| Single-leaf max size | Up to 2800 × 2600 mm (SL155) | Max for your glass weight |
| Thermal value (sliding) | None published | Calculated Uw for your glazing |
| Air / water / wind grade (sliding) | Not per series | Test report for your configuration |
| Field | What to write | If left blank |
|---|---|---|
| Total opening W × H | ____ mm × ____ mm | Factory guesses, leaf count wrong |
| Arrangement (O / X) | ____ (e.g. OXXO) | Opening fraction assumed, not designed |
| Glazing build-up | ____ (e.g. 8+1.52PVB+8) | Max leaf width overstated |
| Wall lay-up outside–inside | ____ / ____ / ____ mm | Wrong series chosen for depth |
| Threshold type | ____ (8 / 43 / 45+85 mm) | Water line not matched to site |
| Stacking side clearance | ____ mm each side | Large opening not achievable |
Only in a stacking layout. A fixed-end OXXO four-panel opens about one-half — the same as a two-panel OX. The count does not set the opening; the arrangement does.
At the published 2800 mm leaf width on SL155, four leaves reach roughly 11200 mm total. The real cap is the roller rating against your glass weight, so confirm the max leaf width for your build-up.
Frame depth is a property of the series profile, not the rail count. SL155 four-track is 155 mm; SL126 / 182 three-track is 182 mm. Check wall thickness against the series, not the number of rails.
Sliding leaves seal by contact at the meeting stiles; lift-slide (SL126 / 182) adds compression when closed. No whole-unit thermal value is published for the sliding series — request a calculated figure for your glazing.
For openings past about four metres, and whenever the head track carries a very heavy total glass load, yes — get the lintel and sub-floor checked before the wall is built.
Not with the current ALPES sliding range — there is no pocket option. A stacking four-panel reaches about three-quarters to nine-tenths open, leaving one leaf width in view.
