Any street in London, whether a Victorian or Georgian terrace, is characterised by its windows. The thin painted frames, the generous ratios, the silent grace of the vertical sliding mechanism. None of this is accidental. It is the product of a window design refined over three centuries and still outperforms modern alternatives in period settings. With proper maintenance, quality timber sash windows last well over 50 years.
Timber is the only suitable material that meets the planning requirements and architectural integrity for homeowners in conservation areas, listed buildings, and as period properties across London and the South East. What is immediately obvious is the visual distinction between a correctly specified timber replacement and a uPVC substitute in a period street, and, in many areas, this has direct implications for planning permission.
Here is a guide that covers what makes timber unique, its current market prices, when to choose repair over replacement, and what to look for in a specialist installer.
What makes timber sash windows different from other window types?
Open a timber sliding sash window, and you know why the design has endured three centuries. No hinges are swinging into the street. The top and bottom lower sashes slide up and down against one another within the box frame and are balanced by weights concealed within it. Sash cord is used in older properties. Whereas newer installations use spring balances that do the same work in less space. Anyhow, the flow is smooth, the sight lines are straight, and nothing is protruding from the wall face.
Timber also pulls off something that no manufactured materials can imitate. It can be cut, shaped, and constructed to fit any historic profile a property needs. An ovolo moulding or glazing bar layout that has not been in mass manufacture in 100 years can be reproduced by a joiner using a physical template. The timber sash windows are bespoke, and species such as Accoya, with its 50-year rot credit, offer the same thermal performance, which makes them worth having.
How much do timber sash windows cost in the UK?
The timber sash window cost varies by timber species, glazing specification, window size, and whether the property is in a conservation area. Below is a table showing the current market rates in the UK.
| Type | Cost Range | Notes |
| Supply only | £1,000 to £1,500 | Standard customised unit, designed with redwood or Accoya |
| Supply and install | £1,500 to £2,500 | Fitting, draught sealing, and hardware |
| Conservation replica | £2,500 to £4,000+ | Profiles matching, specialist glazing, and planning compliance |
| Repairs (minor) | £150 to £300 | Replacement of the cord, draught proofing, frame adjustment |
| Repairs (major) | £400 to £800 | Rot treatment or full sash overhaul |
Timber sliding sash windows prices in London are usually within the following ranges due to accessibility limitations and the higher prevalence of conservation needs.
When is repair the right choice for timber sash windows?
Timber windows have a certain lifespan, but not all sash windows need to be replaced with age. Timber sash window repairs are a more preferable choice when the structural frame is not worn or damaged.
The decision to repair or replace is made based on a single question: Is the timber solid? If it is, repair preserves original fabric and is much less expensive than replacement. If decay is too extensive and the profiles are too old to restore economically, a like-for-like replacement from a reputable timber window company would be a better, longer-term investment.
What sizes are available and can they be made to measure?
The timber sash windows are available in standard sizes ranging from 450mm to 1,200mm wide and 900mm to 1,800mm high. Ideally, period properties do not have uniform openings. Most quality installations are therefore manufactured as bespoke timber sash windows to the exact aperture size. Before manufacturing, measurements are checked, the condition of the box frames is verified, and access requirements are identified.
Whether buying from a timber sash windows London specialist or a national timber window company, one must always demand a site survey before placing an order.
Conclusion
A window is not a minor detail. It is one of the most prominent and structurally important elements of a period property. Getting it right entails selecting a material that enhances the architecture, meets planning expectations, and has a lifespan of decades without deterioration. Timber does all of that. It is maintainable, repairable, and thermally competent, and with suitable specification and maintenance, it has a higher lifespan than any other option. The decision to install quality timber sash windows is a choice to preserve a building’s character and value in the long term.
SJB Sash Windows brings professional expertise and ancient skills to all its projects, whether it be a single window replacement or a whole-property installation throughout London and the South East. The company established a reputation for accuracy in joinery, the use of the highest-quality, sustainably sourced timber, and the treatment of all buildings with the care and attention they deserve.
