Architecture first
We start with the building, its proportions and the details that make the façade work.
The Box Sash story · Established 1979
Built on one obsession: getting the window right.
For more than four decades, Box Sash has focused on bespoke timber joinery that respects the architecture, performs properly and is made to last.
1979Where the story began
50 yearsTimber-frame guarantee
Made in BritainManufactured by Box Sash
British timber joinery
Made in BritainBritish manufacturing
FENSARegistered installation
FSCResponsible timber
50
Year guaranteeTimber-frame reassurance
Where it began
A founder’s belief that traditional windows could be better.
In 1979, founder our founder set out to improve the traditional sash window without stripping away the proportions and character that made it worth preserving in the first place.
That meant treating a window as part of the architecture, not simply a hole to fill. The sightlines, meeting rails, glazing bars, horns, mouldings, timber, glass and finish all had to work together.
That philosophy still shapes Box Sash today: understand the building first, then make the joinery around it.
1995A double-glazed sash construction method reached a patent milestone — evidence of a long-standing focus on improving performance without compromising traditional form.
Our standard
Quality is at the heart of what we do.
It is not a marketing line added after the fact. It determines how a project is surveyed, specified, manufactured, finished, installed and supported.
Made, not merely supplied
Box Sash manufactures bespoke timber windows and doors rather than relying on a generic bought-in frame.
Details are the product
Timber sections, glazing, bars, mouldings, horns, hardware and finish are considered together.
Installation matters
A beautiful product only works when the survey, fitting and final adjustment are treated with the same care.
Today
Made in Wales. Made by Box Sash. Made for the building.
Today the Box Sash team operates and manufactures in Wales, combining traditional joinery knowledge with modern glazing, security and finishing techniques.
Manufacturing our own product gives us control over the part that matters most: the finished result. The window or door can be specified around the house rather than forcing the house around a standard product.
- Made to measureSpecified around the individual opening and property.
- Solid timber craftsmanshipTraditional joinery with modern performance where it helps.
- One specialist companySurvey, manufacture and installation considered as one project.
- Long-term confidence50-year timber-frame and 10-year glazing guarantees.
Why homeowners choose Box Sash
Confidence comes from knowing who is responsible.
For a significant project, trust is not just a review score. It is knowing who is making the product, who is fitting it and who stands behind it afterwards.
A long trading history matters when the product is designed to last for decades.
British manufacture and specialist timber joinery are central to the Box Sash proposition.
Long-term timber-frame reassurance, backed by a clear stated guarantee.
Period architecture, timber proportions and detailing are the focus — not one-size-fits-all replacement windows.
Customer confidence
What matters is how the finished project feels.
★★★★★
“Professional service and excellent product. OBSW were able to specify windows that other companies said were impossible.”
Edward Christie★★★★★
“No hesitation in recommending them.”
Bill Swan★★★★★
“The windows are stunning- excellent quality and the installation was so smooth and straight forward.”
Jill Benjoya MillerSee the standard
Quality that shows in the finished home.
Different products, the same principle: the joinery should feel as though it belongs to the building.
Built for homeowners who want it done properly
Choose a company that cares how the house looks when the work is finished.
Tell us what you are considering and we’ll help you understand the right timber solution for the property.