Every sliding door in this family carries the same two words in its name, and they are the two words in the catalogue that mean the least. Heavy-duty is not a property of a door. It is a claim that three separate numbers are true at the same time, and a catalogue can only print two of them.
The SL112/167 multi-functional heavy-duty sliding door is a good place to watch this happen, because its three numbers point in three different directions. One of them is larger than the same number elsewhere in our catalogue, one of them is smaller, and one of them is a range so wide that quoting it without a condition is close to meaningless. Read together, they tell you more about how a sliding door is actually engineered than any adjective can.
| What the catalogue prints | What it actually measures | What it does not tell you |
|---|---|---|
| Single sash driving capacity up to 220 kg | How much sash the hardware is stated to move along the track | Whether 220 kg is a roller rating, a permitted working load, or a tested sash weight, and at which glass build-up |
| Profile thickness 1.8 to 2.5 mm | The wall of the aluminium section, which differs by member and by application | Which member the 1.8 belongs to, which one the 2.5 belongs to, and which of them is carrying your panel |
| Glass sash thickness 43 mm | The depth of the sash stack: glass, gasket, bead and the aluminium holding all of it | How thick a glass unit the rebate will accept. Forty-three millimetres is the stack, not the slot |
| Not printed at all: the working load after margin | The figure your design should actually run at | The gap between a rating and a working load is a selection decision, and it belongs in writing |
The word heavy-duty does exactly one useful job. It tells you to ask for three numbers instead of one. It does not tell you what they are, and it certainly does not tell you that they measure different things.
SL112 and SL167 are not two products that happen to share a page. They are one profile system, and the number is the frame wall width you get at a given track count: 112 mm for the single-track and two-track builds, 167 mm for the three-track build. Order an SL167 and you have ordered a three-track configuration of a series that also ships as an SL112.
This is not an exotic convention, it is just rarely explained. A publicly listed heavy-duty sliding series from another maker uses the same device: 130 mm for its two-track version, 195 mm for its three-track version, and one series name over both. When the number in a sliding door name is large, the first question is whether it is a size, a depth, or a track count.
It matters here because 167 sounds like a dimension of the door you are buying, and it is a dimension of the frame you are burying in the wall. Nobody sees it once the jambs are closed. A nominal callout such as a 72 x 80 entry door is a name for a door rather than a dimension you can build to, and SL167 works the same way.
One thing about our own catalogue is genuinely counter-intuitive and worth stating before a contractor sets a jamb: frame depth is a property of a series, not a function of track count. Our four-track sliding door has a 155 mm frame wall width, while the three-track SL126/182 has 182 mm. More tracks does not reliably mean a deeper frame.
| The number | What it really is | Who needs it |
|---|---|---|
| 112 / 167 | Frame wall width, the dimension that goes into the wall | Whoever sets the jamb, the reveal and the finishes |
| Overall frame width and height, in millimetres | The dimension that is manufactured | The factory, and the purchase order |
| Clear opening when the panels are stacked | The dimension you walk through | The person who has to live with the room |
All three get called the size in an email. Only the second one can be manufactured.
The published line is single sash driving capacity up to 220 kg. Read the verb. Driving is about moving. It is not the same sentence as carrying.
A sliding panel asks two different questions of its hardware. The rollers have to hold the panel up without deflecting, flat-spotting or pressing a permanent dent into the track over thousands of passes. And something has to start that mass moving, along a track that will one day have grit in it, on an afternoon when the frame has grown. Those are two engineering problems, and they are answered by two different numbers.
One publicly published roller selection guide puts the gap between them at roughly forty percent. It sizes carriages so that each one runs at about sixty percent of its rated capacity, leaving margin for dynamic load, track debris and deflection. The reason given is worth repeating: in that guide's own words, roller failure is almost always a specification error rather than a manufacturing defect, because the rating was taken at the static sash weight with no allowance for anything else. If you take one question out of this section, take that one. Is your 220 kg a rating, or is it the load you are permitted to run at?
There is a second version of the same confusion inside our own catalogue, and it is worth being blunt about. Our SL155 thermal break sliding door publishes a 400 kg load capacity with a twenty-wheel self-balancing pulley. SL167 publishes 220 kg. The larger number is not the better door. It is a different measurement taken on a different mechanism, and putting both in one column and sorting descending is the most common way a sliding door catalogue gets misread.
A rating is per sash, and a sash is mostly glass. Glass weighs roughly 2.5 kg per square metre for every millimetre of glass thickness, a rule of thumb published by more than one hardware and glazing source. A 6+24A+6 unit carries twelve millimetres of glass in total, so around thirty kilograms per square metre before the frame, the hardware and the beads are added. Set that against 220 kg and you arrive somewhere around six to seven square metres of panel, depending on how much aluminium the sash carries.
That is our arithmetic using a published rule of thumb, not a product claim. It exists to make one point: the moment you change the glass, the number you were quoted stops describing your door. Maximum panel sizes are published against an assumed glass build-up. Upgrade the glass and the maximum comes down, on every slider from every maker, whether or not the catalogue says so.
| Ask | Why | An answer that sounds fine and is not |
|---|---|---|
| Is 220 kg the rating or the permitted working load? | They differ by a margin that is somebody's selection decision | It is heavy duty |
| Per sash, or per door? | A three-panel door has three sashes and three sets of hardware | The door takes 220 kg |
| At which glass build-up? | Glass is most of the mass the hardware ever sees | Standard glazing |
| How many carriages, and what is each one rated at? | Load is shared, and one worn wheel is not a fifty percent failure | Twenty wheels |
Here is the number that looks like a mistake. SL167 has a glass sash thickness of 43 mm. Every other sliding product we list is thicker. The series that carries heavy-duty in its name has the thinnest sash we build in this category.
It is not a contradiction, and understanding why is worth more than any adjective in the product name. Take aluminium out of a sash and three things happen at once. The sash gets lighter, which is exactly what you want when the mechanism that has to move it is rated at 220 kg. More of the opening becomes glass and less of it becomes metal, which is what people actually mean when they ask for a panoramic door. And the bending resistance that the removed aluminium used to provide has to be found somewhere else, which is where the frame-enclosing-sash structure in the next section earns its place.
Heavy-duty here is not extra material. It is the same material, moved to the member that can use it.
One honest limit follows directly. The 43 mm figure is the stack, not the slot. What decides how thick a glass unit you can fit is the rebate, the channel the glass actually sits in, and that is a dimension on a section drawing rather than a number in a specification table. The catalogue lists 24 A insulated glass for this series. If your project wants a thicker build-up, a laminated inner pane, or an asymmetric make-up to move a resonance dip, the answer is on the drawing or it does not exist yet.
| Series | Glass sash thickness | Sash width | Frame wall width | Single sash rating published |
|---|---|---|---|---|
| SL112/167 multi-functional | 43 mm | 53 / 75 mm | 112 / 167 mm | 220 kg driving capacity |
| SL155 thermal break | 54.5 mm | 44.5 mm | 155 mm, four track | 400 kg load capacity |
| SL126/182 (96) | 55 mm | 96 mm | 126 / 182 mm | Not published |
| SL126/182 (75) | 55 mm | 75 mm | 126 / 182 mm | Not published |
| TS130 side press window | 55 mm | 75 mm | 130 mm | 200 kg load-bearing pulleys |
The two numbers in the sash width column for SL167, 53 and 75, are the second place where one name hides two configurations. Ask which width sits on which panel, because the answer changes what you see when the door is closed, and a door is closed far more than it is open.
The catalogue line reads frame-enclosing-sash structure design, interlocked, reinforced. It sounds like copywriting. It is the answer to the problem the thin sash created in the previous section.
Under negative wind pressure, the suction on the windward face that tries to pull a panel out of its track, exactly three things hold a sliding sash: the rollers at the bottom, the guide at the head, and the interlock where two panels overlap. There is no hinge, and there is no continuous compression around the perimeter the way a casement sash has. So the geometry of that overlap, and the stiffness of the frame receiving it, are structural numbers rather than aesthetic ones.
Wrapping the sash with the frame puts the deeper section on the outside of the assembly and lets the interlock work as an interlock instead of as a butt joint. It is also why an anti-lift device belongs in the specification rather than the options list: a panel that can be lifted out of its track is a panel that has stopped being held by anything at all.
The trade is legible once you know where to look. You get a narrower sash and more glass, and you pay for it with a frame that has to be detailed properly into the wall. That is a good trade on a wide opening and a poor one on a wall nobody has drawn yet.
SL167 carries a 45 mm high-ｄｒｏｐ bottom track, with an optional 85 mm high water barrier. Nothing else in our sliding programme is built that way. The SL126/182 series offers a 43 mm high track or an 8 mm low track, and that is a choice made at the point of order.
A high-ｄｒｏｐ track is two decisions in one piece of extrusion. The ｄｒｏｐ is a dam, and its height is the depth of water the threshold will hold before it comes inside. The same ｄｒｏｐ is also the step you cross every time you use the door.
Here is the part most product pages will not say, and it changes how the number should be read: on a sliding door the outer track is designed to get wet and to hold water until the drainage takes it away. Water standing in the outer channel is the system working. Water that crosses the inner dam is a leak. A 45 mm ｄｒｏｐ is not a defect and it is not an inconvenience the factory forgot to design out. It is the height of a line that has to be somewhere, and on this series it is at forty-five millimetres.
The honest cost is accessibility. Forty-five millimetres is a step, and an 85 mm water barrier is a considerably bigger one. If the opening has to be level for a wheelchair, a pram or a trolley, that has to be said before the profile is ordered rather than after the floor is screeded. On a sheltered opening the 8 mm low track on the SL126/182 series exists for exactly this reason, and choosing between the two is a question about your site, not about which door is better.
The reason to accept a 167 mm frame depth is the third track. On a two-track slider, at most half the opening can be clear, because one panel parks behind the other. Add a third track and two panels can stack to one side, and public guidance from several markets puts the clear opening at roughly two-thirds of the width. One supplier's stacking door page states the two-thirds figure outright and pairs it with a minimum overall width, because below a certain span the extra track buys very little.
Two-thirds is not all of it, and the difference is permanent. There will always be one panel of glass in the opening, and on a three-track door there are two interlocks in your line of sight instead of one. If the brief is a wall that disappears, no number of tracks will get you there. That is a different product family, and a nominal folding size such as a 36 folding door is a name for a configuration rather than a door you can order from the number alone. Ask us what is actually in the folding programme today.
There is a real secondary benefit though, and it is structural rather than spatial. Splitting a very wide opening across three panels keeps each panel at a sensible weight, which is precisely what the 220 kg figure in section three is there to protect. The same motive appears on the other side of the catalogue: our four-track door exists because at some width, fewer panels means each one is too heavy to move.
| Dimension | Two track (112 mm frame) | Three track (167 mm frame) |
|---|---|---|
| Clear opening | About one half | About two thirds, per public third-party guides |
| Panels still in view when open | One | One |
| Interlocks in the sightline | One | Two |
| Frame depth into the wall | 112 mm | 167 mm |
| Panel weight at the same total width | Heavier per panel | Lighter per panel |
| Bottom track | 45 mm high-ｄｒｏｐ | 45 mm high-ｄｒｏｐ |
Profile thickness for this series is published as 1.8 to 2.5 mm. That is the widest range in our catalogue, and it is not a tolerance band. It is two different doors.
The reason sits in the same line of the catalogue that calls the product multi-functional: flexible fixed and movable panel configuration for doors and windows. A panel serving as a window and a panel serving as a door are not asked to do the same work, and the section is not the same. Quoting 2.5 mm when the member in question is a non-load-bearing bead, or accepting 1.8 mm on the member that is actually carrying the panel, are two ways of making one number mean two things.
Wall thickness is also measured on a defined member, standards differ on which member, and some define the measurement over the coating while others take it on bare metal. The fix is unglamorous and it works: name the member, name the number, and say whether the figure is bare metal or finished.
A range is not a specification. It is a list of specifications, and someone has to say which one you are buying.
SL167 lists a mechanical sealing system and a window sash sink design. Both are attempts at the same problem, and the problem is worth stating plainly because it is the reason sliding doors get judged unfairly.
A sliding panel has to have clearance in order to roll. That clearance is why a sliding sash seals by contact, using brushes, fins and wipes, where a casement sash seals by compression against a continuous gasket. Australian sliding-door guidance puts it directly: sliding doors are inherently harder to seal than hinged ones because the sash has to move inside the frame. So when a sliding product claims casement-level sealing, the honest reading is better than a plain sliding sash, not it is a casement. Then ask the three questions that turn the claim into a number: which report, which standard, and was the test specimen the operating configuration rather than a fixed panel. Fixed panels almost always test better, and they are not what you are buying.
A mechanical seal is also a mechanism, which means it has a state. A panel that is closed but not locked, or locked but never adjusted, is a panel with an expensive gasket sitting next to a gap. The corollary is maintenance-shaped rather than complaint-shaped: most sliding door sealing complaints in year two are an adjustment problem, not a failure. Whoever performs the first adjustment, and whoever owns it in writing, belongs in the order.
We have written elsewhere about what 6060-T66 actually is: that the temper is a process claim rather than a measurement, that it needs a quench at the press exit and a recorded ageing cycle, and that it is one of the easiest things to print on a brochure and one of the easiest to check on a sample cut. This is the short version for SL167 in particular.
The alloy and temper are the same across the ALPES catalogue, which makes them a floor rather than a differentiator. 6060-T66 will not help you choose between SL167 and SL155, because both have it. What it does tell you is the opposite of what people assume: T66 at 1.8 mm and T66 at 2.5 mm are the same temper on two very different doors, which is exactly why section eight exists.
The temper is also not a performance rating. It says nothing about air, water or wind. It is a materials statement, and on a panel this size the performance questions are answered somewhere else entirely.
| Situation | Why it goes wrong | What to ask about instead |
|---|---|---|
| You need a level threshold | The 45 mm high-ｄｒｏｐ is a step by design, not by oversight | The 8 mm low track on SL126/182, or a recessed detail agreed before the floor is set |
| The whole opening has to clear | Three tracks clear about two thirds, and the last panel never leaves | A folding set, and a written answer on what our folding programme currently offers |
| The jamb is shallow | 167 mm has to go somewhere, and finishes thicken the wall without thickening the frame | SL112 at 112 mm, or a confirmed build-up with an extension frame |
| You want the thickest glass unit available | 43 mm is the stack, and the rebate is the limit | The rebate dimension on the section drawing, and SL126/182 at 55 mm if the build-up wins |
| Panels have to come out for service or glass replacement | The rollers, the head guide and the interlock are all that hold a sliding sash | Whether the fixed panel is removable or direct-set, and what the removal sequence is |
| The brief calls for a hinged panel with handing | This is a slider; it has no handing to specify and no swing arc to draw | A swing product. We do not currently list one, so a right hand swing door enquiry is a different conversation entirely |
| Item | What is published | What you still need | Why the gap exists |
|---|---|---|---|
| Alloy and temper | 6060-T66 across the range | A mill certificate tied to your production charge | It is a process claim, and the process is the only thing that can be inspected |
| Profile thickness | 1.8 to 2.5 mm | The measured figure for the load-bearing member on your configuration | A range is a list of specifications, not one specification |
| Frame wall width | 112 mm single and two track, 167 mm three track | Your jamb depth, and whether an extension frame is required | It is a depth into the wall, not a dimension of the opening |
| Glass sash thickness | 43 mm | The rebate dimension on the section drawing | 43 mm is the stack, and the slot is a different measurement |
| Sash width | 53 mm and 75 mm | Which width sits on which panel | Two configurations are sold under one name |
| Insulated glass | 24 A | The full build-up, and the sash weight it produces | Glass is most of the mass the hardware ever sees |
| Single sash rating | 220 kg driving capacity | Whether it is a rating or a working load, and the per-carriage split | The two differ by a margin that is a selection decision |
| Bottom track | 45 mm high-ｄｒｏｐ, optional 85 mm water barrier | Whether the ｄｒｏｐ is a dam or a step on your detail | Both are true at the same time, and only your site decides which one matters |
| Drainage | High-ｄｒｏｐ track for instant drainage | The drainage route drawn as a path, not as a closed box | Water management is a route through the section, not a feature on a list |
| Sealing | Mechanical sealing system, sash sink design | The test report, the standard, and whether the specimen was the operating sash | Contact seals and compression seals are not the same claim |
| Air, water and wind performance | Not published for this series | A calculated or tested value for your size, glass and track count | Without a declared threshold, saying it leaks is an argument rather than a measurement |
| Maximum panel size | Not published | The size for your glass build-up and track count, in writing | It is a function of the glass, not a property of the series |
| Line | What to write | An answer that sounds reasonable and says nothing |
|---|---|---|
| 1. Track count and configuration | Three track, from left: fixed, sliding, sliding | Standard configuration |
| 2. Overall frame width and height | Two numbers in millimetres | About three metres |
| 3. Glass build-up | 6+24A+6, low-e coating on surface three | Double glazed |
| 4. Resulting sash weight per panel | A number in kilograms | It is heavy duty |
| 5. Rating versus working load | State both, in the same units | Rated 220 kg |
| 6. Number of carriages and rating each | A count and a kilogram figure per carriage | Twenty wheels |
| 7. Load-bearing member thickness | Millimetres, and bare metal or finished | 1.8 to 2.5 mm |
| 8. Threshold | 45 mm high-ｄｒｏｐ, or low track | Weathertight |
| 9. Drainage route | Show it on the section drawing | It has drainage |
| 10. First adjustment after handover | A named party, in writing | The installer |
No. It is the same series in a three-track build. 112 and 167 are frame wall widths at different track counts, and the one you get depends on how many panels you want moving.
Because they are not the same measurement. One is stated as a driving capacity and the other as a load capacity on a twenty-wheel self-balancing carriage. Ask for both in the same units, for the same glass build-up, before you compare them.
Ask for the rebate dimension on the section drawing. The 43 mm sash is the stack, not the slot, and glass, hardware and maximum panel size have to be specified together because changing any one of them moves the other two.
Not on this track. The 45 mm ｄｒｏｐ is the inner dam that holds water out, and removing it removes the reason the track is built that way. If a level threshold is a requirement, say so before the profile is chosen.
The temper is a materials statement with a defined minimum, and it is a floor rather than a differentiator. What decides the door is wall thickness on the load-bearing member, section geometry, the frame-to-sash relationship and the hardware that carries the panel.
It should be, and it usually is not. Most sliding door sealing complaints in the second year are adjustment rather than failure, and an unnamed adjuster turns a five-minute job into a dispute.
