Double Glazed Sash Windows London

Yes. Timber sash windows can be fitted with slimline double glazed units — typically 4mm glass with a 2–4mm gap — that sit within the original frame without altering the window's appearance. Where frames are beyond saving, we manufacture bespoke new timber sashes pre-fitted with double glazing.

Slimline double glazing uses very thin sealed units designed to fit into the shallow rebates of period timber sash frames. They provide meaningful thermal improvement over single glazing while being virtually indistinguishable from the original glazing. No bulky frames, no change to the window's appearance.

Double glazing a timber sash window in London typically costs £650–£1,300 per window (ex-VAT), depending on size, frame condition, and whether retrofit or full replacement is required. See our full sash window price guide for a complete breakdown.

Yes. We replicate the original glazing bar profiles exactly — whether your windows have horns, ovolo mouldings, or a specific bar pattern. Once painted, slimline double glazed sash windows are indistinguishable from the single-glazed originals. Preserving your home's character is non-negotiable for us.

In most London conservation areas, slimline double glazing in timber frames is acceptable to planners because it maintains the original appearance. We have worked in conservation areas across Islington, Hackney, Camden, Richmond, Kensington, and more. We know each borough's policies and will advise you before any work begins.

Listed buildings require Listed Building Consent for changes to windows. While it is more complex, slimline double glazing in a sympathetically reproduced timber frame is increasingly accepted with the right supporting documentation. We can advise on and support your planning submission.

uPVC sash windows are thicker, have different sightlines, and look visually incorrect on period properties. They are rarely permitted in conservation areas and actively reduce the value and character of Victorian and Edwardian homes. Timber is longer-lasting when properly maintained, fully repairable, and genuinely period-correct. We build sash windows the right way.

Yes — double glazing provides a meaningful improvement in acoustic insulation over single glazing. For maximum noise reduction, we recommend combining double glazing with our draught-proofing system, which eliminates the air gaps that carry most street noise. Together, they can reduce perceived noise by up to 40%.

Both address different problems. Draught proofing eliminates cold air coming through gaps in the frame — often the biggest source of heat loss. Double glazing improves the glass itself. For the best result we recommend both. Many clients are surprised how warm properly draught-proofed single-glazed sash windows can be — it is sometimes all that is needed.

A slimline retrofit into existing frames typically takes 1–2 days per window. Full bespoke new timber sashes take 2–4 weeks to manufacture, plus 1–2 days per window for installation. We always agree a programme with you before starting — no surprises on lead times or disruption.