Sliding windows are the most widely specified window type in Indian homes, and the reason is spatial rather than aesthetic: nothing swings into the room or out over a balcony.
In a flat where every square metre is accounted for, that matters more than most performance differences.
How the track system works
Sashes run on rollers along horizontal tracks set into the bottom of the frame. The number of tracks determines how the window can be configured and how much of it opens.
Two-track
Two sashes, each on its own track, sliding past one another. Maximum opening is half the total width, because one panel always sits behind the other.
The standard arrangement for bedrooms and most residential windows. Simple, economical, and adequate for the great majority of openings.
Three-track
Three sashes on three tracks. Two panels can stack behind the third, so up to two-thirds of the width opens.
Used for wider living room openings and balcony accesses where a larger clear opening is wanted. The frame is deeper to accommodate the third track, which is one reason wider openings need a deeper series.
Four-track and beyond
Used on large-format openings, typically with two panels stacking to each side. Frame depth increases again, and both glass weight and roller specification become critical.
Matching series to opening
Eumax manufactures five sliding series, and the millimetre figure is the depth of the frame section rather than anything visible from inside the room.
- 50mm — smaller and secondary openings: bathrooms, utility areas, small bedroom windows facing internal courtyards. A deeper section here adds cost without adding useful performance.
- 60mm — the general-purpose residential series, suitable for most standard bedroom and living room openings in two- or three-track configuration.
- 80mm and 88mm — wider spans, balcony openings, upper floors facing open ground, and three-track units carrying more glass weight than a 60mm section should.
- 108mm — large-format glazing, full-height sliding doors and commercial-scale applications where span and glass weight exceed residential requirements.
Depth governs how many internal chambers fit in the section, how much glass thickness the sash can carry, and how far the profile can span before it needs to be stiffer. Specifying one series across a whole house guarantees that some openings are over-specified and others under-specified.
Rollers and glass weight
The component that determines whether a sliding window still works smoothly in year ten is the roller, and it is invisible on a finished window.
Rollers carry the full weight of the sash — frame, glass and hardware — through every cycle. A double-glazed unit weighs substantially more than a single pane, so a window specified for double glazing needs rollers rated for it. Cheap nylon rollers under a heavy sash flatten and start to drag within a few years.
Stainless steel or heavy-duty bearing rollers cost more and last considerably longer. If the window is large, or double glazed, or will be used daily, this is worth asking about specifically.
The other half of the equation is the track itself. Debris in the track grinds the rollers every time the sash moves, which is why track cleaning is the single most valuable maintenance task on a sliding window.
Honest limitations
Two things a sliding window does less well than a casement, worth knowing before specifying.
Sealing. A sliding sash seals with a brush or pile strip against the track, and that strip must stay soft enough to allow movement. A casement sash compresses a continuous gasket. The difference matters for noise, dust and air-conditioning load — which is why road-facing and air-conditioned rooms are usually better served by casement.
Claims that sliding windows eliminate drafts overstate this. They reduce air leakage substantially compared with an old or poorly fitted window; they do not seal like a compressed gasket.
Opening area. A two-track window opens to half its width. A casement opens fully. Where natural ventilation is the priority, that is a real difference.
Where sliding is clearly right
- Tight spaces — nothing swings, so furniture, curtains and balcony railings are all unaffected.
- Balcony and terrace access — a sliding door does not consume usable balcony space.
- Wide openings — three- and four-track configurations handle spans a casement cannot.
- Upper floors in windy positions — no sash to be caught and slammed by a gust.
- Anywhere cost matters and the sealing advantage would not be used.
Specifying a sliding window well
- Choose the series for the opening size, not for consistency across the house.
- Decide the track count from how much clear opening the room actually needs.
- Confirm roller specification, particularly if the sash is large or double glazed.
- Check reinforcement covers both frame and sash members.
- Ask about drainage in the bottom track — this is where monsoon water leaves, and blocked drainage is the most common cause of a leaking window.
- Reserve casement for the rooms that need it. A mixed specification is usually the right outcome.
A well-specified sliding window in a suitable position will run smoothly for decades with almost no attention beyond keeping the track clean. A badly specified one — under-depth for its span, or under-rollered for its glass — will start dragging within a few years, and by then the only fix is replacement.
Frequently asked questions
How much of a sliding window actually opens?
A two-track window opens to half its width, because one panel always sits behind the other. A three-track opens to about two-thirds. A casement window opens fully, which is worth weighing where natural ventilation is the priority.
Which uPVC sliding series should I choose?
The 50mm series suits small and secondary openings such as bathrooms and utility areas. The 60mm series handles most standard bedroom and living room windows. The 80mm and 88mm series are for wider spans, balcony openings and exposed upper floors, and the 108mm series is for large-format glazing and full-height sliding doors.
Why do sliding windows become hard to move over time?
Almost always the rollers or the track. Debris in the track grinds the rollers every time the sash moves, and cheap nylon rollers under a heavy sash flatten and start to drag within a few years. Keeping the track clean is the single most valuable maintenance task, and specifying rollers rated for the glass weight prevents the problem at source.
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