Guillotine Glass or Sliding Glass? Glass Systems Compared
Guillotine glass panels move vertically and leave the opening completely clear when open. Sliding glass panels move horizontally and allow partial opening, but occupy space at one end. The right choice depends on the proportions of the opening and whether there is room for panels to stack.
How the Two Systems Work
In guillotine glass the panels are raised inside vertical rails and locked at any height. In sliding glass the panels move horizontally between top and bottom rails on wheeled carriers. The difference is not only direction; where the panels sit when open differs too.
In guillotine glass the panels are concealed at the top and take up no space in the horizontal plane. In sliding glass they gather to one side and stack there. That distinction becomes decisive on narrow balconies.
Space Use and the Opening
Sliding glass needs no swing clearance, unlike hinged systems, and preserves usable space on narrow balconies. Guillotine glass leaves the opening completely clear when open, which is an advantage where an uninterrupted view matters.
- Narrow, long balcony: sliding glass is usually more practical
- Tall, narrow opening: guillotine glass suits better
- No side space for panels to stack: guillotine glass
- Partial opening used frequently: sliding glass
Panel Sizes and Limits
In guillotine glass, panel height ranges from 2.4 to 3.5 metres depending on the system, and panel width from 60 to 100 centimetres depending on glass thickness. Wider openings use several panels side by side with intermediate posts kept as slim as possible.
In sliding glass the panel count depends on the width of the opening and the rail system. Frameless models fold the panels to one side when opened, so more panels can be used.
Insulation and Sealing
In both systems single glazing offers limited insulation, with a thermal value around 5.7 W/m²K. With double glazing this drops to 1.1-2.8 W/m²K and acoustic insulation reaches 38 dB.
Frameless sliding systems prioritise appearance and their insulation is limited; they block wind and dust but thermal insulation should not be expected.
| Feature | Guillotine | Cleanable Guillotine | Sliding |
|---|---|---|---|
| Direction | Vertical | Vertical | Horizontal |
| Panels when open | Concealed above | Concealed above | Stacked to one side |
| Max panel height | 3.5 m | 3 m | System dependent |
| Water tightness | IP65 | IP55 | System dependent |
| Acoustic insulation | 28-38 dB | 28-38 dB | 28-38 dB |
| Cleaning outer face | From outside | From inside | From outside |
Cleaning: The Overlooked Criterion
Reaching the outer face of the glass on upper floors is a serious problem and is rarely considered at the point of purchase. This is why cleanable guillotine glass exists: panels can be removed or tilted inwards so the outer surface is cleaned from inside the building.
At ground level, where the facade is easy to reach, standard guillotine glass is both more economical and better sealed (IP65 against IP55). The decision should follow the height of the floor and the ease of facade access.
Safety and Child Protection
Both systems use tempered safety glass, which breaks into small blunt pieces rather than sharp shards. Locking options include single or multi-point locks and a child safety lock. On motorised models obstacle detection stops movement if something is in the way.
- Tempered glass: reduces injury risk if broken
- Multi-point lock: resists forcing
- Child safety lock: prevents accidental opening
- Obstacle detection: prevents trapping on motorised systems
- Keeping the remote out of children’s reach is recommended
Motorised or Manual?
In guillotine glass the lifting mechanism can be spring assisted, hydraulically damped or motorised. Spring and damped models need no electricity and are unaffected by power cuts. Motorised models use 200-400W tubular motors and become practical as panel weight increases.
Spring Assisted
The most economical option. On small and medium panels it operates comfortably with one hand. It needs no electricity, so power cuts are not an issue and the failure surface is small.
Hydraulically Damped
The panel slows and lowers itself, removing the risk of slamming. Recommended on heavy panels and in homes with children.
Motorised
Preferred on tall, heavy panels or where many panels need to be controlled together. Offers remote control, wall switch and group control, and allows sensor integration.
Installation Details and Common Mistakes
In glass systems, performance is usually determined by installation quality rather than the glass itself. A rail that is out of level makes the panel stiff and tires the mechanism over time. If drainage is planned badly, water collects in the bottom profile.
Rail Alignment
The bottom and top rails must be exactly parallel. Even millimetric deviation makes the panel bind at one point; users describe this as "the glass got heavy" but the problem is not in the glass.
Drainage
There are drainage channels in the bottom profile and they must stay open. Drainage holes sealed with silicone cause water to collect inside the profile and lead to corrosion over time.
Seal Selection
Brush seals and rubber seals do different jobs. A brush seal blocks dust but passes water; where sealing is needed, rubber is required. Confusing the two is the most common installation error.
Decision Guide
Three questions decide the choice: the proportions of the opening, whether there is space for panels to stack, and how easily the outer facade can be reached. Once these three are answered, the right system usually becomes obvious.
Balcony on an upper floor
Cleanable guillotine glass. If the facade cannot be reached, cleaning becomes a problem that is hard to solve later.
Ground floor terrace
Standard guillotine or sliding glass. Because the outside is easy to reach, the extra cost of the cleanable model is not needed.
Narrow, long balcony
Sliding glass. Partial opening is practical in daily use and there is usually room at one end for the panels.
Conclusion
Guillotine glass leaves the opening completely clear and is superior on tall, narrow openings. Sliding glass allows partial opening and is more practical on long, narrow balconies. On upper floors the cleaning criterion enters and the cleanable model comes forward.
The two systems can also be used in the same project — guillotine on one elevation and sliding on another. During the survey we measure the proportions of each opening and give a separate recommendation per elevation.