Georgian Sash Windows
The elegant simplicity of Georgian design: six-over-six glazing, slim profiles, and classical proportions that defined a century of British architecture.
Last reviewed: 15 June 2026 | 3 min read
What defines Georgian sash windows
The Georgian period (1714-1830) established the sash window as the dominant window type in British architecture. Key characteristics:
- Six-over-six glazing: each sash divided into six panes by slim glazing bars
- Slim profiles: timber sections typically 50-65mm, creating delicate appearance
- Flush frames: window frames set flush with external brickwork, not recessed
- Cylinder glass: hand-blown glass with slight distortion and ripples
- Proportions: typically taller than wide, following classical ratios (often 4:3)
Evolution through the period
Early Georgian (1714-1750): Frames often flush with wall face. Glazing bars quite thick by later standards (20-25mm). Sometimes nine-over-nine panes.
Mid-Georgian (1750-1800): Glazing bars become slimmer (15-18mm). Windows gain more refined proportions. Introduction of Building Act 1774 required frames to be set back 100mm from wall face for fire safety.
Late Georgian/Regency (1800-1830): Glazing bars at their slimmest (12-15mm). Some larger houses adopted two-over-two panes with much larger glass sheets.
Why Georgian windows are worth preserving
Original Georgian sash windows from the 1700s remain in working order across Bath, London, and other period towns. The hand-blown glass contributes significantly to building character. Replacement with modern units removes this historic value irreversibly.
For listed buildings, consent for replacement is rarely granted unless the originals have failed structurally. Conservation officers will insist on repair.
Common issues and repairs
The slim sections make Georgian windows vulnerable to rot where water collects. Bottom rails and sills most affected. Splice repairs preserve maximum historic fabric. Replacement should be a last resort when more than 40% of timber is decayed.
- Historic England, "Traditional Windows" guidance (2017)
- Georgian Group, "Windows" technical note
- SPAB, "The Repair of Wood Windows"