If you own a period home, you already know how much your sash windows contribute to its character. You also know that single panes and tired timber can be chilly in winter, noisy on busy streets and expensive to heat. Double‑glazed sash windows solve those day‑to‑day frustrations without sacrificing the look you love. The question we’re asked most often is simple: What do double glazed sash windows cost in 2026?
This guide explains the main factors behind cost, sets out typical ranges for double‑glazed sash windows, and helps you plan a realistic budget, whether you’re replacing a single box or an entire façade. We’ve also included practical tips for comparing quotes and choosing the right team for the job.
What drives the cost of double glazed sash windows today?
No two homes, or windows, are identical, which is why costs vary. In 2026, the biggest influences on double‑glazed sash windows costs are set out below.
Scope of work
There are two main routes. Complete sash windows replacement renews the whole timber assembly (box frame and sashes). Sash replacement keeps a sound box frame in place and swaps in new, double‑glazed sashes. Sash replacement is usually less disruptive and preserves original boxes, while a full renewal resets everything for maximum longevity and airtightness.
Size and count
Taller or wider openings use more timber and glass, which increases material and labour. Whole‑house projects often benefit from economies of scale. Bays, wide panes and large stairwell windows can also require extra hands and specialist lifting equipment.
Glazing specification
Choices such as slimline double glazing, acoustic or laminated glass, warm‑edge spacers and gas fills influence the final figure. Higher‑performance glass adds comfort but increases weight, which may mean heavier counterweights or upgraded balances.
Joinery detail
True glazing bars, ovolo mouldings, sash horns and bespoke architraves add craft time and therefore cost. Intricate profiles take longer to machine and finish, and they demand additional care during spray finishing.
Access and site conditions
Upper floors, restricted parking or the need for scaffolding can increase labour time and price. Local parking suspensions, scaffold licences or timed deliveries may also be required and will be itemised where relevant.
Property status
Listed buildings or homes in conservation areas usually require like‑for‑like detail and approvals, which adds specialist time and materials. Allow a little extra in the timeline for drawings, heritage photos and consultation with the planning team.
Finish
A factory spray finish, colour matching inside and out, and specialist ironmongery improve durability and appearance, with a modest cost uplift. Factory finishes typically outlast site painting, reducing maintenance in the first decade.
Location
London projects generally carry slightly higher labour and logistics costs than the UK average. Travel time, parking constraints and delivery windows can affect scheduling and, in turn, the overall price.
Typical price ranges in 2026
To keep things clear, here’s how we structure our services:
- Complete replacement – the full box sash window is made new. From around £2,000 + VAT per window.
- Sash replacement – new, hand‑made double‑glazed sashes fitted into your existing, sound box frame. From around £1,250 + VAT per window.
At Wandsworth Sash Windows, quotes typically include professional installation and a factory spray finish on new joinery; we also arrange waste removal. Every installation comes with a 10‑year guarantee. Your written proposal will confirm all inclusions. When comparing offers, it’s worth checking that fitting and disposal are included, or getting a separate figure, so you’re weighing like for like.
A quick note on materials: our workshops are UK‑based and our timber is sourced from FSC‑certified suppliers. Many homeowners want their choices to be sustainable as well as beautiful; timber ticks both boxes.
At‑a‑glance guide (per window, typical London townhouse sizes)
| Specification | Sash replacement (keep box) | Complete replacement |
| Standard slimline double glazing, factory spray finish | from £1,250 + VAT | from £2,000 + VAT |
| With acoustic/laminated glass upgrade | from £1,450–£1,650 + VAT | from £2,200–£2,500 + VAT |
| With decorative bars/horns & colour match (in/out) | from £1,500–£1,800 + VAT | from £2,300–£2,700 + VAT |
Figures are typical starting points; final costs depend on survey, sizes and site access.
The exact price for your home always comes from a tailored survey and quote. We offer this free of charge and with no obligation, and we’ll fold every cost into a single, fair figure so you can decide with confidence.
How home type affects the budget
Different properties present different challenges. Here’s a helpful rule‑of‑thumb overview of sash window double glazing cost by scenario:
- Terraced homes – Generally, the most straightforward. Front elevations are often accessible from the street and rear from the garden. Expect pricing close to the guide figures.
- Flats and maisonettes – Access and permissions matter. Coordinating with managing agents, arranging parking or scaffolding and working within communal areas can add to labour time.
- Semi‑detached and detached houses – Larger elevations and bay windows are common; the joinery is often more detailed and may increase material and fitting time.
- Listed buildings & conservation areas – While Wandsworth Sash Windows does not service listed buildings, we have experience in what affects the cost. Slimline or heritage‑approved glass, authentic mouldings and careful approvals add craft time, planning support and sometimes specialist glass.
London vs the rest of the UK
People often ask about double‑glazed sash windows costs in London compared with elsewhere. London projects carry slightly higher labour and logistics costs (parking, access and delivery constraints). The uplift isn’t dramatic, but it’s real. On the flip side, London buyers place a premium on well‑presented period façades, so the investment is frequently recouped in curb appeal and resale value.
Why choose timber over uPVC, and what it means for value
Comparisons with uPVC (a rigid, durable form of PVC commonly used in construction) are inevitable. While uPVC can cost less on day one, wooden double‑glazed sash windows bring advantages that repay you over time:
- A longer service life. High‑quality timber, maintained correctly, can outlast plastic alternatives by decades. Timber can also be repaired and refinished, extending its life further.
- Authenticity. Real wood looks and feels right in period architecture. Buyers notice, and valuers do too.
- Sustainability. Responsibly sourced timber stores carbon and can be recycled at the end of life. uPVC manufacture and disposal are more resource‑intensive.
- Comfort and performance. Double‑glazed timber sashes deliver excellent thermal and acoustic results, with the added benefit of natural insulation from the frame itself.
When you spread the cost across that longer lifespan, and consider the effect on curb appeal, the pound‑for‑pound value of timber is strong.
Optional extras that change the price
Upgrades are never mandatory, but some are popular because of the comfort and security they add:
- Glazing options: Low‑E coatings, warm‑edge spacers, argon fill, and laminated or acoustic glass for busy roads
- Security: Sash stops (also known as restrictors) are normally included within our quote as standard, although they may not by other companies. You could also opt for different locking mechanisms or laminated glass units for ground floors
- Detailing: True or applied glazing bars, horns, bespoke mouldings and heritage‑accurate profiles
- Finishes: Dual‑colour (different inside/outside), and premium ironmongery
Worked examples (to help you budget)
1) Victorian terrace, front elevation only (three windows)
Sash replacement with slimline double glazing, factory spray finish, new cords and ironmongery.
Indicative total: £3,900–£5,400 + VAT (mix of sizes and any minor access considerations).
2) Whole‑house upgrade, five to eight windows
Combination of complete replacements to damaged boxes and sash replacements to sound frames; colour‑matched finish; laminated glass to street‑facing rooms.
Indicative total: £10,000–£18,000 + VAT depending on sizes and access.
3) Listed cottage (four windows)
Like‑for‑like joinery detail, heritage‑approved slimline units, conservation‑grade putty lines, planning liaison.
Indicative total: £7,000–£11,000 + VAT subject to approvals and glass choice.
These scenarios are illustrative. Your survey will always produce a tailored figure for your home.
Energy savings and running‑cost benefits
Double glazing slows heat loss dramatically compared with single panes. Combine that with tight draught‑proofing and a precise fit, and you’ll feel the difference the first cold evening. Over a full heating season, many customers report noticeable reductions in fuel use. Add the quieter rooms and the ease of opening/closing, and everyday life simply becomes more comfortable.
Getting accurate quotes (and avoiding surprises)
A good quote should be easy to read and compare. We recommend asking for:
1) A measured survey – so sizes and details are crystal clear.
2) An itemised breakdown – joinery, glazing specification, ironmongery, finish, fitting, disposal and any access equipment.
3) Lead times and guarantees – factory schedules, paint system details and written warranty terms.
4) Compliance & certification – FENSA certificate where frames are replaced, and insurance‑backed guarantee paperwork (QANW IBG) for new joinery.
5) Proof of provenance – where the joinery is made, what timber is used and sustainability credentials (e.g., FSC).
6) References and aftercare – recent local installations you can view, and availability for servicing.
At Wandsworth Sash Windows, all new joinery is hand‑made in our UK workshops, fully spray finished and installed by our own long‑standing team. Your quote will set out inclusions clearly, and our 10‑year guarantee is provided in writing.
The bottom line
Timber sash windows do an outsized job: they shape the way your home looks, feels and performs every single day. If you’re weighing up the double‑glazed sash windows cost this year, focus on lifespan, comfort and craftsmanship rather than day‑one price alone. With well‑made joinery and a careful installation, the investment returns value in warmth, quiet, curb appeal and reliability for years to come.
When you’re ready, we’ll come out, measure up and provide a clear, itemised proposal for your home. Book a free survey and let’s craft a plan that balances quality and budget without compromising the character that drew you to your home in the first place.