Secondary Glazing for Sash WindowsSlimline, Vertical-Sliding Heritage Units
Keep your beautiful original timber sashes and add a discreet, vertical-sliding second layer that cuts noise, eliminates draughts and improves warmth — with no change to the external appearance and no planning permission required.
Designed to Match Your Sashes
Sash windows are one of the defining features of London's Georgian, Victorian and Edwardian homes — but single-glazed timber sashes are draughty, noisy and cold. Replacing them is rarely permitted in conservation areas, and never desirable when the originals are sound. Vertical-sliding secondary glazing is the answer: a bespoke internal unit that slides exactly like your sash, so you keep the look and operation while gaining modern performance.
| Feature | What it means for you |
|---|---|
| Vertical-sliding operation | Both sashes slide just like your original window, so daily use feels identical. |
| Slimline sightlines | Narrow aluminium frames align with your meeting rails to stay visually discreet. |
| Full access retained | Lift out or slide open for cleaning, ventilation and fire-escape access. |
| Colour-matched finish | Powder-coated to any RAL colour to blend with existing joinery. |
The Benefits for Sash Window Owners
- Draught elimination. Sealed units stop the air leakage that makes old sash boxes so cold — see our guide to solving Victorian sash draughts.
- Noise reduction. Paired with acoustic laminate glass, a wide air gap cuts traffic noise by up to 80%.
- Keep the originals. Find out why secondary glazing beats replacing sash windows for cost, heritage and disruption.
- Vertical-slider specifics. Read more about our vertical-slider units for sash windows.
Product Options for Sash Windows
Although the vertical-sliding unit is the natural partner for a traditional box sash, it is not the only option. During your free survey we assess how each window is used, how often it is opened and whether fire-escape access is required, then recommend the format that gives the best seal without compromising day-to-day convenience.
- Vertical sliders. The default choice for sash windows. Two sliding panes mirror the movement of your original upper and lower sashes, so both halves still open for ventilation. Balances and brush seals keep the action smooth and draught-free for years.
- Hinged casements. Ideal where a sash is rarely opened or sits above a radiator or deep sill. The unit swings inwards on concealed hinges for full access to the primary window behind, then closes onto a continuous compression seal for maximum acoustic performance.
- Lift-out panels. The slimmest, most discreet solution for windows that are almost never opened, such as those on a landing or in a rarely-used room. The panel simply lifts away when seasonal access is needed and delivers the tightest possible seal the rest of the year.
Why Choose Us for Your Sash Windows
Sash windows are unforgiving — an ill-fitting unit looks obvious and slides poorly. Every unit we make is bespoke-manufactured to the exact dimensions of the individual opening, because no two period sashes are truly identical. Frames are powder-coated to match your existing joinery so the addition all but disappears against the original window.
Our fitters are heritage specialists who understand how box sashes are built, so installation is clean, precise and non-destructive — nothing is cut, drilled through original timber unnecessarily, or left unable to be removed later. Every project begins with a free, no-obligation survey where we measure each sash, discuss glass specification and give you a transparent written quote. The whole system is fully reversible, protecting both the fabric and the value of your period home.
Explore the full range of secondary glazing types, check costs, or return to our complete guide to secondary glazing. We fit sash window secondary glazing across London and every borough we serve.
Secondary Glazing for Sash Windows: FAQs
Common questions about fitting secondary glazing to original timber sash windows.
What Our Clients Say
Rated 4.9 out of 5 across 127 reviews from London homeowners.
"Exceptional service from start to finish. The noise reduction in our Kensington townhouse is remarkable — we no longer hear the constant traffic on the high street, even in the front bedrooms."
"Specialists who truly understand listed buildings. They handled our Grade II* property with real expertise and managed the conservation paperwork so we didn't have to worry about a thing."
"Our Georgian sash windows were draughty and freezing every winter. The secondary glazing has transformed the house — warmer rooms, lower heating bills, and the original windows look untouched."
"From survey to installation the team was professional and tidy. The fit is so discreet that visitors don't even notice the secondary glazing is there. Sleep has never been better."
"We live near a busy junction and the difference is night and day. The acoustic glass they recommended cut the noise dramatically. Worth every penny for the peace and quiet."
"Honest advice, fair pricing, and beautiful craftsmanship. They talked us through every option without any pressure. I would recommend them to anyone with a period property."
Protect Your Sash Windows the Smart Way
Book a free survey and we'll measure each sash, recommend the right specification and give you a clear, no-obligation quote.