Does sliding secondary glazing reduce noise as well as fixed panels?

Almost. A correctly sealed horizontal slider with compression gaskets performs within 2-3dB of an equivalent fixed panel. Budget sliders using brush-pile seals lose 4-6dB, which is why the seal specification matters more than the opening style itself.

How wide can a sliding secondary glazing panel be?

Each individual pane can be up to 1.2m wide and 2.4m tall. Wider openings are covered by three or four pane configurations running on a multi-track, so a 3.6m bay can be glazed without any fixed sections.

Can I still open my original sash window behind it?

Yes. Slide the secondary panel to one side and the primary window is fully accessible for opening and cleaning. This is the main reason sliding is specified on around 70% of our London installations.

How much does sliding secondary glazing cost in London?

A standard two-pane horizontal slider with 6.4mm acoustic laminate starts at £480 per window supplied and fitted. Upgrading to 10.8mm laminate adds £120-£180 per window and gains a further 4-6dB.

Sliding Secondary Glazing London

The most-specified opening style in London — full window access without removing a panel.

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51dB

Peak noise reduction

100mm+

Recommended cavity

£480

From, per window

2-3 hrs

Typical install time

Sliding secondary glazing is the default choice for the overwhelming majority of London installations. Panels run on a low-friction track inside a slim aluminium outer frame, so you can open the secondary unit exactly the way you open the primary window behind it — no lifting, no storage, no two-person handling.

We supply both horizontal sliders (two, three or four panes running side to side, ideal for wide Victorian and Edwardian casements) and vertical sliders that mirror the movement of a traditional box sash. Every unit is glazed with 6.4mm or 10.8mm acoustic laminate and sealed against a compressed EPDM gasket, so the acoustic performance is not compromised by the moving parts.

Horizontal vs vertical sliding

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.

Horizontal: 2, 3 or 4 panes; best for casements and wide bays
Vertical: spiral-balanced; mirrors the original sash movement
Both accept 6.4mm and 10.8mm acoustic laminated glass
Both allow full access for cleaning the primary window

Why sliding units keep their acoustic seal

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.

Where sliding works best in London homes

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 system specification

Frame: Slim thermally broken aluminium, powder-coated to any RAL
Glass options: 4mm float, 6.4mm acoustic laminate, 10.8mm acoustic laminate
Noise reduction: Up to 51dB with 10.8mm laminate at 150mm cavity
Seals: Compression EPDM at jambs, interlocking meeting stiles
Max panel size: 1.2m wide x 2.4m tall per pane
Configurations: 2, 3 or 4 pane horizontal; 2 pane vertical

Pricing guide

Specification	Price	Notes
Standard casement, 6.4mm laminate	from £480	Up to 1.2m x 1.2m, 2-pane horizontal
Sash-height vertical slider, 6.4mm	from £560	Up to 1.0m x 2.0m
10.8mm acoustic laminate upgrade	+£120-£180	Per window, adds 4-6dB
3 or 4 pane wide opening	from £720	Openings over 1.8m wide

All prices supplied and fitted in London, inclusive of survey and 25-year warranty. See the full secondary glazing price list.

Case study: Four-pane sliders on a Fulham Road flat

Fulham, SW6

Problem: Bus route directly outside; 74dB peaks measured at the glass line, 62dB inside the living room.

Solution: Four-pane horizontal sliders with 10.8mm acoustic laminate at a 130mm cavity across three front windows.

Result: Interior level fell to 33dB — a measured 29dB reduction, with the windows still fully openable for summer ventilation.

Frequently asked questions

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