Sliding Secondary Glazing London

Horizontal sliders are the better acoustic and practical choice on wide openings. Weight is carried by the bottom track, so panes up to 1.2m wide stay easy to move even when glazed with heavy 10.8mm laminate. Vertical sliders suit tall Georgian box sashes where the original window opens upward and you want the secondary unit to behave identically.

The common objection to sliders is that a moving panel cannot seal as tightly as a fixed one. That is true of budget systems with brush-pile seals. Our sliders use a compression gasket at the jamb and interlocking meeting stiles, which closes the flanking path that costs cheaper systems 4-6dB.

Combined with a decoupling cavity of 100mm or more, a correctly specified horizontal slider measures within 2-3dB of an equivalent fixed panel — a difference most people cannot detect, and a fair trade for daily usability.

Bedrooms on busy roads, first-floor drawing rooms in period terraces, and any window you actually open in summer. If the window is rarely opened — a stairwell, a light well, a top-floor dormer — a fixed or lift-out panel will give you a slightly higher dB figure for less money.

Sliding units are the most forgiving opening style to retrofit, but they are also the least forgiving of a bad measurement. The track has to sit dead level or the panels drift, so the first thing our surveyor does is check the reveal for wind and fall across the full opening width. London reveals in Victorian and Edwardian stock are rarely square: 8-12mm of variation corner to corner is normal, and it is absorbed in the frame packing rather than by forcing the track.

We then record the cavity you can realistically achieve. The air gap between the primary glass and the secondary panel is the single biggest driver of low-frequency performance, and a sliding system needs enough reveal depth to carry the track without fouling the original window furniture, shutter boxes or working sash cords. Where the reveal is shallow we face-fix onto the architrave and make up the depth with a sub-frame instead of compromising the gap.

The survey is delivered as a written specification: frame finish, glass build-up, cavity depth, achievable dB reduction range and any joinery preparation the window needs first. It is the same document we hand to the fitting team, so what you approve is what gets installed by our secondary glazing installers London team.

Sliding panels are glazed with acoustic laminate rather than toughened float, because the interlayer damps the coincidence dip that makes ordinary glass transparent to traffic noise. 6.4mm laminate is the standard specification and handles general urban noise well. 10.8mm laminate is the acoustic upgrade and is what we specify for arterial roads, bus routes and anything within earshot of a rail corridor.

Where the aim is thermal as well as acoustic, we can glaze with low-emissivity coated laminate, which reflects long-wave heat back into the room while keeping the acoustic interlayer. It costs more per panel and it is only worth it on rooms you heat continuously — a north-facing living room or a permanently occupied home office rather than a spare bedroom.

Whatever the glass, the panels seal against a compressed EPDM gasket on all four edges. A sliding system that whistles is almost always a sealing failure, not a glass failure, which is why the gasket line and the brush seal at the meeting stile matter as much as the laminate thickness.

Day to day, a slider should take one hand and no thought. Panels run on stainless bottom rollers with a top guide, and they lift out of the track without tools for cleaning the outer face of the primary glass — normally a twice-yearly job in central London, more often on a main road.

Maintenance is limited to keeping the bottom track clear and occasionally wiping the gasket. There are no cords, weights or springs to service. The system carries our 10-year standard warranty, extended to 25 years on Premium and Heritage specifications, covering the frame, the moving gear and the sealed glass units.