Sash Window Cost UK 2026: Repair, Restoration + Replacement by Material

UK sash window costs Q2 2026 per window: draught-proofing £150-350, repair/re-cord £120-300, full refurbishment £250-650, uPVC replacement £500-1,100, timber replacement £600-1,400, Accoya replacement £900-1,600. Slim-profile heritage double glazing adds £150-400. A full Victorian terrace (8-12 sashes) is £3,000-16,000 depending on repair vs replace. London/SE +20-30%.

Repair + draught-proof if: the property is listed/conservation, original timber is sound, you value authenticity (£400-1,000 per window all-in). Replace if: extensive rot beyond economic repair, non-listed property (uPVC allowed), you want modern double glazing. Original Georgian/Victorian sashes in good timber outlast modern replacements when maintained — restoration is often the better long-term value AND mandatory for listed buildings.

Sash window draught-proofing costs £150-350 per window in 2026 (Mighton, Reddiseals systems). The specialist routes brush seals into the frame + replaces parting/staff beads, eliminating draughts + rattle while retaining the original window. For a full house (8-12 windows) expect £1,200-3,500. Draught-proofing typically cuts heat loss through the window by 50-70% and is the most cost-effective heritage-friendly thermal upgrade — far cheaper than replacement and reversible.

Almost never. Listed buildings require Listed Building Consent for any window change, and conservation officers virtually always reject uPVC in favour of timber. In conservation areas (not listed), uPVC sash may be permitted if it closely matches the original, but many councils have Article 4 directions requiring timber. For listed + conservation properties, timber (redwood, sapele) or Accoya is the safe choice. Always check with your local conservation officer before ordering.

For listed + long-term-hold properties, often yes. Accoya (acetylated modified timber) costs £900-1,600 per sash vs £600-1,400 for redwood, but comes with a 50-year above-ground guarantee, doesn't swell/shrink (so paint lasts longer), and resists rot completely. It's increasingly the conservation officer's preferred replacement timber. For a property you'll own 15+ years, the longevity + reduced repainting frequency justifies the premium. For a shorter hold, quality redwood is fine.

Yes — slim-profile double glazing (units as thin as 10-14mm) can be retrofitted into original or new timber sashes, adding £150-400 per window. Heritage-approved units (Slimlite, Histoglass) satisfy most conservation officers + some listed building applications. The thermal improvement is substantial (U-value from ~5.0 single to ~1.6-2.0 slim-double). An alternative for listed buildings where even slim units are refused is secondary glazing (£200-500 per window) — a discreet internal pane that's fully reversible.