| Action | Cost (per window, approx) | Lifespan | Planning Permission | | :--- | :--- | :--- | :--- | | | £400 – £800 | 30–50 years | Not required | | Replacement (timber) | £1,200 – £2,500 | 30 years | Required & unlikely | | Replacement (uPVC) | £600 – £1,000 | 15 years | Forbidden (Conservation) |
Hampstead is not just a postcode; it is a conservation area icon. From the slopes of Hampstead Heath to the historic Flask Walk, the architectural vernacular is defined by one feature: the sliding sash window. However, the humid microclimate of North London’s hillside and the age of these structures (many dating back to 1700–1850) mean that sash windows here are under constant stress.