Why Stacking Doors Need a Maintenance Plan and Casements Do Not

A casement window carries its sash on hinges that are loaded in a fixed direction and are rarely moved. A stacking door does the opposite: every panel rides on wheels, every opening pushes those wheels across a track that collects whatever the weather carries in, and every closing compresses a seal that has to stay elastic for a decade. The duty is continuous, the environment is dirty, and the components are small.

That combination is why stacking doors develop faults and casements do not. It is also why the faults are almost never structural. The frame does not fail; the wheels wear, the track fills, and the seals harden. All three are maintenance items, and all three are far cheaper to service on a schedule than to repair after the door has been dragging for a year.

This article covers the three systems in the order they fail, the adjustment procedures that restore them, and the specification questions to ask at purchase so that maintenance is actually possible later.

System One: Rollers and Their Load Path

In a stacking door the panel weight does not hang from the frame as it does in a hinged door. It is carried down through the stile to a bogie, and from the bogie to wheels running on the track. Every kilogram of glass is therefore a rolling load, concentrated on a wheel maybe 30 mm across.

A single glazed panel in a stacking door commonly weighs 40 to 90 kg. On a four-panel system that is up to 360 kg distributed across eight to sixteen wheels, and each wheel carries its share through a bearing the size of a fingernail. This is the arithmetic that decides how long the system lasts.

The four signs that rollers are past adjustment

1. Drag that increases through the travel. Smooth at the start, heavy at the end, usually means one bogie has dropped and the panel is scrubbing on the track or the lower rail.
2. A clicking or grinding noise. Grit in the race, or a flat-spotted nylon wheel. Grinding specifically points to metal-on-metal contact after the wheel surface has worn through.
3. Uneven gap at the meeting stile. Measure the gap top and bottom when closed. A difference of more than 2 mm indicates the panel is out of level and the load is no longer shared between bogies.
4. The door no longer compresses its seal. Water or draught at the bottom corner while the rest of the perimeter is tight. The panel has dropped below the height at which the gasket was designed to compress.

Height adjustment procedure

Adjustment screws are normally accessible from inside the panel's bottom rail, behind a cover cap, and give around ±3 mm of travel. The order matters.

1. Clean the track first. Adjusting a door that is running on debris gives a false reading and the setting will drift once the debris is removed.
2. Open the panel fully and set it on its bogies, not resting on the track.
3. Adjust the leading bogie and trailing bogie by equal amounts, half a turn at a time. Unequal adjustment tilts the panel instead of raising it.
4. Close the panel and check the meeting-stile gap top and bottom. Target equal gaps, and check the seal compresses evenly along the full height.
5. Repeat across every panel in the stack, working from the fixed jamb panel outward. Adjusting the outer panel before the inner ones shifts the whole stack and undoes the earlier settings.
6. Verify the locking points still engage without forcing the handle. A panel raised too far will bind the multi-point lock, which is the fault most often mistaken for a lock failure.

System Two: Track Contamination and Drainage

Track contamination is the single most common cause of stacking door complaints, and it is also the most preventable. The track is a horizontal channel at floor level in an opening that is designed to let weather in when open. It collects sand, soil, leaf fragments, building dust, salt spray and dead insects, and the wheels compact all of it into an abrasive paste.

That paste does three things at once. It increases rolling resistance, which loads the wheel bearings beyond their rating. It wears the wheel surface, which changes the running diameter and drops the panel. And it blocks the drainage path, which turns a maintenance issue into a water ingress issue.

Drainage path maintenance

Low-threshold and recessed track systems rely on weep openings and a drainage channel beneath the track to move water out of the reveal. Those paths are small and they clog silently. When they block, water sits in the track channel, is drawn up behind the sill by capillary action, and appears inside the building as a damp patch on the floor next to the door — usually blamed on the door rather than on the drainage.

• Clear the weep openings at the ends of the track and any slots in the track wall. A soft brush and low-pressure air is enough; a metal probe can damage the coating.
• Flush the channel with clean water and confirm it exits outside rather than pooling.
• Check the fall of the external paving. If the terrace drains toward the threshold, no track drainage detail will keep up with it.
• In coastal sites, rinse salt from the track monthly rather than quarterly. Chloride in a damp track channel attacks the aluminium surface and the wheel axles together.

Cleaning method that does not make things worse

Vacuum the dry debris before wetting it. Adding water to dust creates a slurry that packs into corners and dries harder than the original deposit. Then wash with warm water and a pH-neutral detergent, rinse thoroughly, and dry the channel. Avoid acid-based cleaners, alkaline degreasers and abrasive pads on anodised or powder-coated surfaces — all three attack the finish, and once the coating is breached the underlying aluminium corrodes in a way that no cleaning will reverse.

System Three: Seals, Gaskets and Brush Strips

Seals do the work that people assume the frame is doing: they keep air, water and noise out, and they hold the panel in position when closed. EPDM is the standard material because it stays elastic across a wide temperature range and resists UV and ozone better than most alternatives. It still ages, and it ages fastest exactly where the duty is highest.

Two notes on seal care. First, the paper test: close the door on a sheet of paper and pull. Consistent resistance around the perimeter means the seal is compressing; a section that slides out freely has lost compression and will leak long before it looks damaged. Second, never lubricate EPDM with silicone spray or petroleum-based products. Silicone can migrate into the compound and change its friction behaviour, and petroleum distorts it. Use a glycerine-based rubber conditioner, or nothing at all beyond cleaning.

Corrosion Care: What Stainless Actually Means

Stainless does not mean corrosion-proof. SUS304 and SUS316 both rely on a passive chromium oxide layer that forms in the presence of oxygen and is self-repairing — as long as it stays clean. In a track channel that holds damp debris, that condition is not met, and chloride from coastal air or from de-icing salts attacks the surface.

The result is tea-staining: a brown surface discolouration that is cosmetic at first and becomes pitting if it is left. SUS316 resists it far better than SUS304, which is why 316 is specified for coastal and marine-adjacent projects, but even 316 stains if it is never cleaned. The maintenance action is simple and is the one most often skipped: rinse stainless components with fresh water at the same interval as the track, and remove any staining early with a non-chloride stainless cleaner and a soft cloth. Never use steel wool or a carbon steel brush on stainless — embedded iron particles rust and create the appearance of a failing component.

The same logic applies to the aluminium frame. Powder coating and anodising are both barrier finishes, and both fail from the inside out once scratched or chemically attacked. Inspect the finish at corners, at fixing points and along the lower rail where impacts from cleaning equipment happen, and touch up damage promptly with a compatible coating rather than leaving bare metal exposed.

Maintenance Schedule

Lubricants: What to Use and What Causes the Problem

Fault Diagnosis: Symptom to Cause to Action

Repair or Replace: The Decision Criteria

Bogies and wheels are consumables and are normally replaced on site without removing the door, provided the system was designed for it. Gaskets and brush strips are cut-to-length replacements. Neither justifies replacing a door.

Replacement of the door becomes the rational answer in three situations: the frame profile itself is corroded through at the lower rail, which happens when a blocked drainage path held water against the finish for years; the track is damaged beyond local repair and is not a replaceable component in that system; or the glass build no longer meets the safety glazing requirement for the location, which is a compliance issue rather than a wear issue. Everything short of those three is maintenance.

Specify for Maintainability at Purchase

Most maintenance difficulty is designed in. These are the questions that determine whether a stacking door can be serviced at all.

1. Are the roller adjustment screws accessible from inside, without removing the panel or the glazing bead?
2. Is the bogie a replaceable cartridge, and is it a standard component or a proprietary one with no aftermarket supply?
3. What is the stated cycle rating of the bogie, and to which standard was it tested?
4. Is the track replaceable in situ, or is it integral to the sill?
5. What is the weep path arrangement, and can it be cleared from the outside without disassembly?
6. Are the gasket profiles standard sections that can be sourced locally, or are they bespoke to the system?
7. For coastal sites, are the wheels, axles, bogie plates and fasteners SUS316 rather than SUS304, and is that stated in the bill of materials?
8. Does the supplier hold a spare parts kit, and for how long after delivery is it guaranteed?

Where the stacking door is part of an automated facade — motorised panels driven by actuators on RS485/Modbus or KNX — the maintenance scope extends to the drive. Check the actuator's duty cycle against the actual number of operations per day, confirm the manual override functions, and verify that the limit positions still match the mechanical stops after any roller height adjustment. Raising or lowering a panel changes where the actuator thinks the door is, and the mismatch shows up as a door that stops short of full seal compression.

Spare Parts Kit Contents

2026 Indicative FOB Prices: Stacking Door Systems and Service Parts

Prices are indicative 2026 factory FOB ranges for project volumes, excluding freight and installation. Service part pricing assumes the system was supplied by Rogenilan Windows Doors and the components remain in production; bespoke profiles and discontinued systems carry a lead time. Final quotation depends on panel count and size, glass build, bogie specification and cycle rating, thermal performance target, coastal hardware grade, and the documentation package required.

Stacking Door Maintenance FAQ

How often should a stacking door be serviced?

Quarterly for a standard site, monthly where the door faces the sea, a busy road or heavy pollen and dust. The difference is not the number of tasks but the interval at which the track is cleared, because the abrasive paste that forms under the wheels is what consumes them. Annual roller height adjustment is enough on most doors, provided the track has been kept clean in between.

Can I lubricate the rollers myself, and with what?

Yes, and dry PTFE spray is the right product. It lubricates without leaving a wet film, so it does not bind dust into the race. Avoid wet grease and oil, which hold abrasive particles against the wheel, and avoid penetrating oils used as lubricants, since they are solvents that wash out whatever lubrication the bogie already had. Sealed-bearing bogies need no lubrication at all; if a sealed bogie is noisy, it is finished rather than dry.

Why does the door still leak after I replaced the seals?

Usually for one of two reasons. Either the panel is out of level, so the new seal is compressing along part of its length only — check the meeting-stile gap top and bottom, and run the paper test along the whole perimeter. Or the drainage path is blocked, so water is arriving inside through the track channel rather than past the seal. Replacing a seal without checking roller height and weep clearance fixes neither.

Is tea-staining on stainless a warranty failure?

Normally not. Tea-staining is chloride contamination of the passive chromium oxide layer, and that layer repairs itself once the contamination is removed. It becomes a material problem only if it is left long enough to develop into pitting. Clean it with a non-chloride stainless cleaner, use a soft cloth rather than steel wool, and shorten the rinse interval so it does not return.

When is it worth replacing the whole door instead of the parts?

When the lower rail has corroded through because a blocked drain held water against the finish, when the track is damaged and is not a replaceable component in that system, or when the glass build no longer meets the safety glazing requirement for its location. Bogies, wheels, gaskets, brush strips and even insulated glass units are all field-replaceable consumables. A door that drags is a maintenance item, not a replacement item.