Sliding window packaging design looks like a cardboard question. It is actually a structural one. A sliding sash is long, heavy, glazed, and it rides on hardware that a forklift can ruin without ever touching the glass. Most transit damage on China-made sliding windows does not happen because somebody used too little foam; it happens because nobody decided, in writing, which part of the unit was allowed to carry its own weight for six weeks at sea. This guide walks through packaging as a specification: what breaks, why it breaks, which crate format answers which sash size, and what to put in the purchase order so that the answer is not a surprise at the port.
A casement sash hangs on hinges and is surrounded by frame on all four sides, so the frame takes the knocks. A sliding sash is different in three ways that all work against it during freight.
None of these problems are solved by adding more bubble wrap. Each one is solved by a specific design decision made before the crate is built.
Almost every claim photograph taken at a destination port falls into one of six patterns. Read the middle column first: it is the part that is usually missing from a supplier's packing description.
| What you see on arrival | What actually caused it | Design feature that prevents it |
|---|---|---|
| Scuffed or polished-looking coating on stiles | Frame-to-frame rubbing under weeks of vibration | A separator between every single unit, plus protective film left on until final clean |
| Opened or cracked corner joint | Point load on one corner during stacking or yard handling | Rigid corner posts and continuous edge board; crates never supported on a corner |
| Glass cracked from the centre outwards | Unit shipped flat and flexing across an unsupported span | Upright, on-edge orientation with support at the stiles only |
| Sash drags or will not roll after installation | Sash weight resting on the rollers for the whole voyage | Sash blocked up so the frame carries the load, or sash shipped separated from the outer frame |
| Bent bottom rail or crushed drainage channel | Fork tine or sling bearing directly on the track | Marked lifting zones on the crate, and a sacrificial channel protecting the bottom rail |
| White bloom or filiform corrosion under the film | Container rain condensed and trapped against the coating, often against damp timber | Dry timber, desiccant, and a moisture barrier that can breathe rather than a fully sealed wet pack |
The one-line test: ask the factory to name the part of the unit that carries its weight while the crate is being lifted. If the answer is "the rollers" or is not given at all, the packaging has not been designed, it has just been applied.
A crate is a consequence, not a decision. Crate length comes from sash width, crate height from sash height, internal blocking positions from sash weight, and the choice of stillage versus crate from how far the largest single sash pushes past what one person or a standard forklift can handle. Below are the sliding models that set those numbers on an ALPES order.
| Model | Frame wall width | Sash / glass build-up | Largest single sash | What the packer must respect |
|---|---|---|---|---|
| TS130 side press window | 130 mm | 75 mm sash, 55 mm glass sash | Project specific | 200 kg pulleys and ROTO side-pressure gear; the side-pressure seal must be shipped in the released position so the gasket is not compressed flat for weeks |
| SL155 thermal break sliding door | Four track 155 mm | 44.5 mm sash, 54.5 mm glass sash | 2800 mm wide by 2600 mm high | A 20-wheel self-balancing pulley rated at 400 kg, and profile at 2.2 to 2.5 mm; this is an A-frame or a two-person stillage size, not a carton |
| SL126/182 thermal break sliding door | Two track 126 mm / three track 182 mm | 96 mm sash, 55 mm glass sash | 2500 mm wide by 3000 mm high | Lift-sliding operation and local reinforcement to 3.0 mm at critical zones; the lifting gear must not bear on those reinforced areas or on the 8 mm low track |
| SL112/167 heavy-duty sliding door | Single/two track 112 mm / three track 167 mm | 53 or 75 mm sash, 43 mm glass sash | Up to 220 kg per sash | 45 mm high-ｄｒｏｐ bottom track with an optional 85 mm water barrier; that projection needs a stand-off or it becomes the load path |
| SL126/182 (75) slim interlock | Two track 126 mm / three track 182 mm | 75 mm sash, 55 mm glass sash, 27A insulating glass | Project specific | 38 mm slim pressure-line-free frame; slim sightlines have less sacrificial material, so separators must be soft and continuous |
Panel count matters as much as panel size. A 2 panel sliding window and a three-panel unit covering the same opening do not pack the same way: the three-panel version puts a fixed centre light between two sliders, which usually changes the balance point and adds an extra interlock stile to protect. Where a project mixes both, the packing list should identify them separately rather than grouping everything under one "sliding window" line.
Export packing specifications published by fenestration manufacturers tend to describe the same sequence. The value is not in the list, it is in the order: each layer fails if the one under it is missing.
The outer format follows from two things only: the largest single sash in the order, and whether the shipment travels full container or as a less-than-container load sharing space with other cargo.
| Format | Best for | Why it works | Where it fails |
|---|---|---|---|
| Corner-protected carton | Single sample units, small sashes, air or express freight | Cheapest, easy to move by hand, no timber rules to satisfy | Almost no stacking strength; collapses in a shared container |
| Fumigation-free plywood crate | Standard sashes, LCL shipments, mixed project orders | Rigid and stackable, and as an engineered wood product it avoids the fumigation certificate that solid wood requires under ISPM-15 | Dead weight in the freight calculation, and disposal cost at the destination |
| Welded steel stillage or iron pallet | Full container loads of uniform sashes | Units stand on edge and are strapped upright, so glass never lies flat; forklift pockets make unloading fast | Return logistics; pointless on an LCL booking |
| Steel A-frame rack | Oversized sashes such as the SL155 at 2800 by 2600 mm and the SL126 at 2.5 by 3.0 m | Glass leans vertically against rubber-cushioned posts and is held by ratchet straps, so panels never contact each other | High cost per unit and needs a real unloading plan at the site |
This is the single most common cause of a sliding unit arriving intact and still not working. Modern heavy sliders carry remarkable loads: the SL155 runs a 20-wheel self-balancing pulley rated at 400 kg, the SL112/167 drives a single sash of up to 220 kg, and the TS130 rides on 200 kg pulleys. Those components are designed for rolling, not for standing still under a static load while a ship pitches for a month.
Two acceptable answers exist, and the factory should tell you which applies to your sizes. Either the sash is blocked up inside the frame so the load transfers to the outer frame and the blocking, or the sash is removed and travels as a separate panel with its rollers protected. What is not acceptable is the default: sash sitting on its wheels, unblocked, with the crate taking the vertical load through the bottom rail.
For the side-pressure TS130 the same logic applies to the seal rather than the wheels. Side-pressure windows achieve casement-grade sealing by pressing the sash against the frame gasket. Shipping that unit with the pressure engaged keeps a resilient gasket compressed for weeks, and resilient gaskets do not enjoy that. Confirm the shipping position of the handle and locking points before the crate closes.
Hardware is where shipping damage turns into installation delay, because a missing transmission box is not a visible scratch you can touch up on site. Handle sets, locking points, rollers, keys and fixings should be packed in a sealed inner box, fixed inside the crate so it cannot migrate, and labelled with the crate number on the box itself. The packing list should then list that box as a separate line against the same crate number.
Screens add a further leaf to the same crate. A china mesh sliding window supplier will normally ship the mesh panel as its own protected leaf rather than leaving it in the track, because stainless steel mesh in a 40# or 80# weave, or the finer anti-PM2.5 mesh, will distort if it is used as a packing surface. Ask whether screens travel in the track or as separate panels, and whether the mesh is covered on both faces.
Finally, ask for a spares allowance in the same shipment. A small number of extra rollers, gasket length, corner keys and a spare handle set costs very little inside a crate that is already going, and it is worth far more than its weight when one component is damaged on a site three weeks from the nearest supplier.
It is worth being honest about the limits, because packaging is asked to solve problems that are not packaging problems.
A perfect crate does not help if it is longer than the site lift, wider than the stair core, or heavier than the crane at the destination. Maximum crate dimensions and maximum crate weight are design inputs that should be agreed before production, not discovered at delivery. On a villa with tight access, that constraint alone may decide between one large crate and several smaller ones.
Packaging also cannot control what happens after the factory gate. If a consolidation warehouse re-stuffs the container, or if the last leg is a flatbed on a poor road, the weakest point in the chain is no longer the crate. This is where a local supplier genuinely still has the advantage: shorter routes, fewer handovers, and a truck that can return the next day. The trade-off for factory-direct supply is traceability and the ability to remake one sash from the original order records rather than replacing a whole elevation, which is exactly why the documentation side of packaging matters as much as the foam.
Packaging only becomes real when it is a line item. Any factory that wants to be treated as the best sliding window company for your project should be able to answer the following in writing, on the quotation, before you pay a deposit. The middle column is what a competent answer sounds like.
| Ask this | Answer you want | Red flag |
|---|---|---|
| How is each sash oriented in the pack? | Upright on edge, supported at the stiles | "Flat is fine, we do it all the time" |
| Are sashes shipped in or out of the outer frame? | Decided by size range and stated in writing | "Whatever is faster to pack" |
| What carries the sash weight in transit? | Frame on blocking, rollers unloaded | No answer, or "the rollers are strong" |
| What separates one unit from the next? | EPE or honeycomb board between every unit | "We put foam in the gaps" |
| Timber type and treatment | Plywood, or solid wood with a valid ISPM-15 mark and certificate | "Wooden crate" with no further detail |
| Per-crate dimensions, net and gross weight | Full packing list issued before container booking | "Approximately" on the quotation |
| Crate numbering and marking scheme | Number on two faces, matching a packing list line | Crates shipped unnumbered |
| Where does the hardware go? | Sealed numbered box fixed inside the crate, listed separately | "In the crate with the window" |
| Maximum crate length and weight | Agreed against your site lift, door widths and crane capacity | Never discussed before delivery |
| Pre-loading evidence | Photo and video set of packing, strapping and container before closing | "We can send photos if there is a problem" |
| Buyer | First priority | Second priority | Do not overspend on |
|---|---|---|---|
| Homeowner, single villa | Corner and film protection, and crate sizes two people can open in a driveway | Numbered hardware box and a small spares allowance | Steel racks you have to return |
| Contractor, multi-unit | Upright stillage and a packing list sequenced to floor or unit, not to model | Pre-load photo report and one named claim contact | Decorative crating that slows the unloading crew |
| Distributor or dealer | Stackable plywood crates sized to your racking, and reshippable for onward delivery | Spare parts kit per crate and consistent numbering across repeat orders | A-frame racks unless you regularly move oversized panels |
Most valid claims are lost at the destination, not at the factory. Four steps protect you, and none of them require special equipment.
Often yes, but only with the rollers unloaded by blocking so the frame carries the weight. For very large or very heavy sashes, shipping the sash as a separate panel is usually safer. Ask which rule applies to your sizes and get it in writing rather than assuming the whole order is packed one way.
Engineered wood such as plywood is generally exempt under ISPM-15, which is why it is widely used for export crating and why it clears customs faster than solid timber. National rules at the destination can be stricter than the international standard, so confirm the current requirement for your port with your broker rather than relying on a general statement.
It should stay on through shipping, installation and any following trades, and come off at final clean. Adhesive films are not designed for long-term exposure to direct sun, so leaving them on a completed façade can make removal difficult. Treat the removal window as part of the handover schedule.
Ask for a loading plan built from the actual per-crate dimensions, not an estimate based on square metres of window. The plan should list crate count, dimensions, gross weight and total volume, and it should be issued before the container is booked. That single document also tells you whether your order is close to a full load or is paying LCL rates for half a container.
Your position depends almost entirely on the evidence gathered in the first twenty minutes: seal number, photographs before unstrapping, and a specific note on the delivery receipt. With those, a remake is usually a straightforward conversation. Without them, it becomes an argument about when the damage happened. Insure the shipment as well, and keep the pre-loading photo set with the claim file.
It is strongly worth it. A small kit of rollers, gasket, corner keys and one spare handle set adds negligible weight to a shipment that is already moving, and removes the usual six-week wait when a single component is damaged or goes missing on site. Specify it in the purchase order so it is packed deliberately rather than added at the last minute.
The difference between "we pack well" and a designed package is four sentences: which way the sash travels, what carries its weight, what separates it from its neighbour, and what number is written on the outside of the crate. Everything else is material choice, and material choice is easy once those four are settled. Send those four questions with your next enquiry, ask for the answers on the quotation rather than in a sales email, and you will have turned packaging from a hope into a line item you can hold someone to.
