Cheapest Way to Replace Sash Windows

The cheapest way to replace sash windows is refurbishment (not replacement), costing £400 to £800 per window compared to £1,200 to £2,000 for new timber sash windows.

Refurbishment cost

£400 to £800 per window (UK, 2026)

New timber sash windows

£1,200 to £2,000 per window (supply & fit)

UPVC sash windows

£600 to £900 per window (supply & fit)

DIY fitting savings

£200 to £400 per window saved

Refurbishment vs Replacement: Which Is Cheaper?

For most period sash windows, refurbishment is significantly cheaper than replacement. A typical Victorian sash window refurbishment includes repairing timber frames, replacing broken glass, fitting new sash cords or spiral balances, draught-proofing, and repainting. This costs £400 to £800 per window depending on the extent of repairs needed.

Full replacement with new timber sash windows costs £1,200 to £2,000 per window (supply and fit, double glazed). Over a full terraced house with 10 sash windows, refurbishment costs £4,000 to £8,000 compared to £12,000 to £20,000 for replacement. That is a saving of £8,000 to £12,000.

Refurbished sash windows, when properly maintained, can last another 30 to 50 years. Original timber sash windows were built from old-growth softwood or hardwood, often higher quality than the timber used in modern replacements. Unless the timber frames are severely rotten (more than 40% decay), repair is almost always more cost-effective than replacement.

When Should You Replace Rather Than Refurbish?

You should replace sash windows rather than refurbish them if:

• Timber rot affects more than 40% of the frame or sill (replacement sections cost almost as much as new frames)
• The window frames are severely distorted or out of square (cannot be draught-proofed effectively)
• You are replacing non-original windows installed in the 1970s or 1980s (often poor quality timber or metal frames)
• The building is undergoing major works and temporary scaffolding is already in place (fitting new windows becomes more cost-effective when access is free)
• Conservation officers or listed building consent require matching period details that cannot be achieved through repair alone

Even in these cases, refurbishment with splice repairs (cutting out rotten sections and splicing in new timber) can still be cheaper than full replacement if done by a skilled joiner. Expect to pay £600 to £1,000 per window for refurbishment with significant splice repairs.

UPVC vs Timber Sash Windows: Cost Comparison

If you must replace sash windows entirely, UPVC sash windows are the cheapest option. UPVC sash windows cost £600 to £900 per window (supply and fit, standard sizes, white UPVC, double glazed). This compares to £1,200 to £2,000 per window for new timber sash windows. The saving is £400 to £600 per window.

However, UPVC sash windows have several limitations:

• Planning permission is usually refused in conservation areas or on listed buildings (officers will specify timber)
• UPVC sash windows do not look like timber sash windows (visible plastic grain, thicker frames, different proportions)
• UPVC cannot be repaired or repainted (scratches and sun damage are permanent)
• UPVC sash windows have a shorter lifespan (20 to 30 years vs 50 to 80 years for timber)
• Resale value impact: period properties with UPVC windows are harder to sell and may sell for less

For a modern house (1960s onwards) or a property outside a conservation area, UPVC sash windows can be a cost-effective choice. For Victorian, Edwardian or Georgian properties, timber sash windows are the better investment despite the higher upfront cost.

DIY Sash Window Replacement: Is It Worth It?

You can save £200 to £400 per window by fitting sash windows yourself rather than paying for professional installation. However, sash window fitting is more complex than fitting casement windows or modern tilt-and-turn windows.

DIY sash window fitting requires:

• Precise measurement of the window opening (tolerance ±3mm for draught-proof fit)
• Weight calculations for sash balances (incorrect weights cause sticking or slamming)
• Trimming and packing to square (old buildings are rarely square)
• FENSA certification for double glazed units (or notifying building control yourself)
• Understanding of meeting rails, parting beads, staff beads and pocket pieces

Poor sash window fitting causes draughts, condensation, sticking sashes and premature failure. Unless you are a competent carpenter or joiner, professional fitting is recommended. The £200 to £400 saving is not worth the risk of a badly fitted window that costs £500+ to rectify.

If you want to save money through DIY, draught-proofing existing sash windows yourself is a better option. Brush seal kits cost £25 to £50 per window and can be fitted by a competent DIYer in 2 to 3 hours per window, saving £150 to £250 in labour costs.

Budget Timber Sash Windows: What to Look For

If you are committed to replacing with timber sash windows but need to keep costs down, look for budget-friendly options that still meet quality standards:

• Standard sizes: off-the-shelf sash windows cost £900 to £1,200 per window. Bespoke sizes add £300 to £500 per window.
• Slim double glazing: 12mm or 14mm double glazed units cost £100 to £150 less per window than 18mm or 24mm units, and they fit better in period properties.
• Softwood, not hardwood: softwood timber sash windows (treated Accoya or engineered pine) cost £200 to £400 less per window than oak or sapele hardwood, with similar longevity when maintained.
• Factory-painted finish: factory-sprayed primer and topcoat saves £50 to £100 per window compared to site-applied paint.
• Spiral balances, not weights: spiral balance sash windows are £100 to £200 cheaper per window than traditional weight-and-pulley systems, and they perform just as well.

Avoid the cheapest imported timber sash windows (often advertised at £500 to £700 per window). These typically use thin timber (44mm not 58mm frames), single glazing or poor-quality double glazing, and inferior joinery that warps or fails within 5 to 10 years. Spending £900 to £1,200 per window on UK-manufactured sash windows with 10-year guarantees is a better investment.

Grants and Financial Help for Sash Window Replacement

Limited grant funding is available for sash window replacement in the UK. Most sash window grants are targeted at low-income households or specific building types:

• ECO4 scheme: covers draught-proofing and double glazing upgrades for low-income households. Does not usually cover full window replacement, but may cover secondary glazing or slim double glazed sash units. Eligibility based on benefits or household income below £31,000.
• Listed building grants: Heritage Lottery Fund and Historic England grants may be available for listed buildings, particularly Grade I or Grade II* properties. Grants typically cover 40% to 60% of costs but have strict conditions on materials and contractors.
• Conservation area grants: some local authorities offer small grants (£500 to £2,000) for heritage improvements in conservation areas. Check with your local planning department.

For most homeowners, grants will not cover sash window replacement. Budgeting for the work through savings, a home improvement loan, or remortgaging is the usual approach.

False Economy: When Cheap Is Too Cheap

Some sash window replacement options appear cheap but end up costing more in the long run:

• Single glazing: saves £150 to £250 per window but loses £100+ per year in heating costs and reduces resale value.
• Imported sash windows below £700: fail within 5 to 10 years (warping, rot, broken balances), requiring early replacement.
• Non-FENSA installers: save £100 to £200 per window but you lose building regulations certification, which can complicate future house sales.
• Skipping draught-proofing: saves £150 per window but allows heat loss equivalent to leaving a small window open 24/7, costing £80 to £120 per year per window in wasted heating.

The cheapest option is refurbishment. If you must replace, budget timber sash windows from a reputable UK manufacturer (£900 to £1,200 per window) are the minimum quality worth buying for a period property. Anything cheaper will likely need replacing again within 10 to 15 years.

Final Recommendation: What Should You Do?

For most period properties, refurbish existing sash windows rather than replacing them. This costs £400 to £800 per window, preserves the original windows, and can last another 30 to 50 years. Get quotes from specialist sash window repair companies (not general builders) who understand traditional joinery.

If the frames are too far gone to repair, install budget timber sash windows (£900 to £1,200 per window, slim double glazing, softwood frames, standard sizes). Avoid UPVC unless you are outside a conservation area and willing to accept the aesthetic and resale value trade-offs.

Use our replacement cost calculator to estimate costs for your property, or see our sash window refurbishment guide for detailed advice on when repair is feasible.

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Last reviewed: 2026-10-26