Sash windows — the vertical sliding style dating back to the 17th century — are the signature feature of Victorian, Georgian and Edwardian UK homes. If you own a period property, you’ll probably need to replace or restore your sashes at some point, and the numbers involved are substantially higher than standard uPVC casement. This guide explains why sash costs more, how the 2026 UK market looks, and how to avoid overpaying.

Typical UK sash window prices in 2026

Per-window installed cost (ex-VAT, including removal of old and fitting):

Material	Low	Mid	High
uPVC mock-sash	£680	£820	£1,100
Engineered hardwood sash	£1,100	£1,400	£1,900
Timber heritage (conservation-grade)	£1,400	£1,850	£2,600
Original-sash restoration (slimline double glazing)	£750	£1,050	£1,500

For a typical Victorian terrace with 8-12 sash windows, full replacement in hardwood sits between £11,000 and £22,000 depending on spec. Conservation-grade timber jobs in listed buildings can exceed £30,000.

Regional variation

• London: +25% (labour and heritage-specialist premium)
• South-East: +10%
• Midlands: baseline
• North of England: −8%
• Scotland: −10% to −12%
• Wales: −10%

Why sash costs 45% more than casement

• Box frame complexity — sash windows have an internal pulley-weight mechanism, not a simple hinge
• Timber quality requirement — low-quality timber warps and jams; you want engineered or accoya hardwood
• Conservation compliance — most period properties are in conservation areas where like-for-like material (timber, not uPVC) may be required
• Slimline double glazing — traditional sash profiles are too narrow for standard 28mm sealed units; slimline 14-20mm units cost more per sq metre
• Fitting time — a skilled sash fitter typically installs 2-3 windows per day vs 4-6 casements

Restoration vs replacement — which makes sense?

If your existing sash frames are structurally sound (no rot, no significant warping), restoration is usually the better option:

• £750-£1,500 per window for slimline double-glazed sash restoration
• Preserves the original wood, original lines, and any listing/conservation compliance
• Better thermal and acoustic performance than unrestored original sashes
• Adds meaningful resale value in conservation areas

If frames are rotten, badly warped, or the wrong glass pattern, replacement is necessary. Always get at least two quotes for restoration vs replacement — the right answer depends on the specific frame condition, which a good installer will assess honestly.

Planning permission for sash replacement

• Listed buildings: always require listed-building consent. Timber-for-timber is usually approved; swapping timber for uPVC almost never is
• Conservation areas: an Article 4 direction may require planning permission for front-elevation changes
• Non-designated period properties: usually permitted development for like-for-like replacement

Frequently asked questions

Can I replace timber sash with uPVC?

Only in non-listed, non-conservation-area properties. uPVC “mock sash” is cheaper (£680-£1,100 per window) and modern profiles are hard to distinguish from timber at casual glance. But in listed buildings or most conservation areas, planning consent will be refused for uPVC.

How long do timber sash windows last?

Engineered hardwood or accoya: 60+ years with standard maintenance (repainting every 5-7 years). Softwood: 15-25 years. Original Victorian pine sashes in good condition can last another 50 years with restoration — that’s why restoration often beats replacement.

What’s slimline double glazing?

Sealed glass units 14-20mm thick (vs standard 28mm) designed to fit within heritage sash profiles that can’t accommodate a thicker unit. Thermal performance is slightly lower than standard double glazing but much better than original single-glazed sashes. Typical u-value 1.6-1.9 vs 1.2-1.4 for standard.

Do new sashes add value to a period property?

Yes, significantly. Rightmove 2025 HomeReport data shows period homes with restored or heritage-grade new sash windows commanding 3-5% higher sale prices than comparable homes with damaged or replaced-with-uPVC sashes. In a £600k Victorian terrace that’s £18,000-£30,000 of resale value — often more than the cost of the work.

Can any FENSA installer fit sash windows?

Technically yes, but sash work is skilled work. Not every FENSA-registered installer handles it competently — especially restoration and heritage-grade. Always specify “sash window” in your enquiry so only sash-specialist fitters respond.

Get four sash quotes

Findfitter matches you with 4 FENSA-registered installers with documented sash-restoration experience in your postcode. Free, no obligation, 2 minutes.

Sources

• FENSA installer register
• Historic England — window replacement guidance in listed buildings
• Rightmove 2025 HomeReport — period property value uplift data