Custom box sash windows
Custom box sash windows London, handmade in our London studio for period and listed homes. Conservation‑grade timber, glazing and draught‑proofing. Request a survey.
If you are looking for custom box sash windows in London, Barnsbury Joinery is a specialist London maker producing bespoke, handcrafted timber box sash windows for period homes, listed buildings, conservation areas and high‑quality developments. Every window is made to measure for the exact opening it will occupy, drawn to the proportions of your property and finished to a standard that mass production simply cannot reach.
From the first survey through design, manufacture and fitting, we handle the whole process in‑house. Our timber box sash windows marry genuine traditional joinery with the thermal performance, security and draught‑proofing that a modern London home needs, so you gain comfort and efficiency without losing a single detail of the building's character.
Where custom box sash windows are made
Our custom box sash windows are made by hand in London. We are a dedicated London studio, not a reseller placing orders with a distant factory, and we do not outsource production to a third party. When you commission a window from us, it is drawn, cut, assembled and finished by our own joiners, using traditional techniques that have been refined to meet contemporary standards.
Being based in London matters more than it might first appear. It means our surveyors can reach your property quickly and return easily if a detail needs checking, and it means the people making your windows understand the housing stock they are working with. London's Georgian, Victorian and Edwardian homes were built in a particular way, with particular timber and particular proportions, and that knowledge is built into everything we produce.
We offer full service in London and the South East, covering survey, manufacture and installation from start to finish. For clients elsewhere in the country we offer supply only across the rest of the UK, providing the same made‑to‑measure box sash windows for fitting by your own trusted contractor. Wherever the windows end up, they are made to the same exacting standard in London.
Why choose custom box sash windows
Custom box sash windows are designed specifically for your property rather than adapted from a limited range of standard sizes. This distinction is particularly important in London, where historic buildings rarely conform to modern dimensions and where openings have often shifted, settled or been altered over a century or more of use. A made‑to‑measure window fills the opening as it actually is, not as a catalogue assumes it should be.
That precise fit brings real, measurable benefits. A window built to the true dimensions of its opening seals properly, which improves thermal performance and cuts the draughts that make period rooms cold and expensive to heat. Because we control the proportions, we can reproduce authentic Georgian, Victorian and Edwardian sight lines, glazing bar widths and meeting rail heights, so the finished window looks right from both the street and the room.
There is also the question of longevity. A handmade timber box sash window, built from good timber and correctly jointed, will comfortably outlast mass‑produced alternatives and can be maintained and repaired indefinitely rather than being ripped out and replaced. And because each window is bespoke, we can integrate modern glazing, discreet security hardware and high‑performance draught‑proofing seamlessly, so the improvements are felt rather than seen. Well‑made timber sash windows combine traditional craftsmanship with modern performance, delivering comfort and quiet without compromising character.
Construction, timber and glazing options
A box sash window is a piece of precision engineering as much as a piece of joinery. The name comes from the hollow boxes built into each side of the frame, which conceal the counterweights that balance the sliding sashes. When the box, the weights, the cords or chains and the pulleys are all correctly sized and fitted, the sashes glide smoothly and hold at any height. Getting this right is the difference between a window that works beautifully for generations and one that sticks, rattles and drops. This is exactly the sort of detail that is lost when windows are produced to a standard specification.
We build our box sash windows from carefully selected, sustainably sourced timber, choosing the species and grade to suit the exposure, the finish and the demands of the specific project. Well‑chosen slow‑grown softwood and premium hardwoods each have their place, and we will advise on the most appropriate option for your property rather than defaulting to whatever is cheapest to buy. Timber is finished with high‑quality microporous systems that protect the wood while allowing it to breathe, and every joint is cut for strength and durability.
On glazing, we offer everything from traditional single glazing with authentic putty lines for the most sensitive listed work, through to slimline and heritage double glazing that dramatically improves insulation while keeping a period‑correct external appearance. We combine this with concealed brush‑pile draught‑proofing that seals the sashes without spoiling their movement, and with security upgrades and modern sash furniture where they are wanted. Because each window is bespoke, these choices are yours to make, and we will guide you through the trade‑offs between authenticity, thermal performance and cost so the specification is right for your home and, where relevant, acceptable to your conservation officer.
London and conservation area expertise
A great many of London's period homes sit within conservation areas or are individually listed, and this is where genuine specialist knowledge earns its place. When a property is protected, the windows are one of the most scrutinised elements of any alteration, because they define so much of the building's character as seen from the street. Getting the detailing wrong can stall a project or lead to a refusal, which is why we treat planning and heritage considerations as central to the design rather than an afterthought.
We work throughout London and the South East on exactly these kinds of buildings. We understand what local planning departments and conservation officers expect to see, and we design sash windows that respect original detailing, glazing bar layouts, sash horns and section profiles so that the replacement reads as correct and sympathetic. Where slimline or heritage double glazing is proposed, we specify it in a way that preserves the external appearance, which is often the deciding factor in whether an upgrade is permitted.
This attention to heritage compliance helps projects progress smoothly and gives homeowners, architects and developers confidence that the windows will be both approvable and long‑lasting. Whether you are restoring a single Georgian townhouse or specifying windows across a larger period development, we bring the same conservation‑grade approach to detailing, materials and finish.
How the process works, from survey to fitting
We keep the process clear, hands‑on and personal, so you always know what is happening and why. Everything begins with a detailed site survey. One of our team visits the property to measure every opening precisely and to assess the building's architectural character, its condition and any features that need to be matched or preserved. Accurate survey information is the foundation of a window that fits perfectly, so we take the time to get it right rather than working from rough measurements.
Next comes design. We tailor the proportions, glazing bar arrangement, timber, glazing specification and finish to your property and to any planning or conservation considerations. This is where authenticity and performance are balanced, and where we make sure the specification will satisfy both your expectations and, if applicable, the requirements of your local authority. You will know exactly what is being made before any timber is cut.
Manufacture then takes place in our London studio, where each box sash window is handcrafted using traditional joinery methods. Finally, our experienced installers carry out the fit, ensuring smooth operation, airtightness and a refined, properly finished result, with care taken to protect the surrounding fabric of the building. From survey to installation the process typically spans several weeks depending on specification and complexity, because quality bespoke joinery is carefully made, not rushed. If you would like to begin, you can request a survey or request a quote and discuss your project with a joinery specialist who values precision, tradition and long‑term quality.
Common questions
How much do custom box sash windows cost in London?
Costs vary with the size of the openings, the level of detailing, the glazing specification and the finish you choose. Bespoke timber sash windows are a long‑term investment, offering a superior fit, greater durability and a more authentic appearance than off‑the‑shelf alternatives, and they can be maintained rather than replaced. For an accurate figure tailored to your property, request a quote and we will price your specific project.
Are timber sash windows better than uPVC?
For period and conservation properties, timber sash windows are widely preferred. Timber allows for finer detailing and authentic proportions, ages gracefully, and can be repaired and refinished over a very long life rather than being discarded. It is also usually the only material acceptable to conservation officers on listed and historically sensitive buildings, where the appearance of the windows is closely scrutinised.
Can box sash windows be double glazed in a conservation area?
In many cases, yes. Slimline or heritage‑style double glazing is often acceptable where the external appearance of the window is preserved, and it can significantly improve insulation and reduce noise. We design windows with conservation requirements in mind and can advise on the glazing options most likely to gain approval for your particular property.
How long does it take to make custom box sash windows?
From survey to installation, timescales typically span several weeks depending on the specification and the complexity of the project. Each stage, from accurate survey and considered design through to handmade manufacture and careful fitting, is given the time it needs. Quality bespoke joinery is carefully made, not rushed.
Do you fit the windows or supply them only?
Both, depending on where you are. We offer full service including survey, manufacture and installation in London and the South East. Elsewhere we offer supply only across the rest of the UK, providing the same made‑to‑measure box sash windows for fitting by your own contractor.
Where are your custom box sash windows made?
Every window is made by hand in our London studio. We do not outsource production, so the joiners drawing, cutting and assembling your windows are the same specialists who understand London's period housing stock and its conservation requirements.
Request a survey
Request a survey for your project, from a single commission to a whole scheme.
Request a surveyA studio of The Barnsbury Group
Barnsbury Joinery is the flagship studio of The Barnsbury Group, a second‑generation heritage joinery house. Established in London in 1987, it makes bespoke joinery by hand and carries the parent voice for the family of studios.
