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London Box Sash Windows

Family run – manufacturing windows in London since 1981

With nearly 40 years of experienced craftsmanship, we create the finest range of sash windows, casement windows and doors – bespoke and tailored to suit your needs.

John Ellis started the business nearly 40 years, when he decided to take his passion for craftsmanship and joinery and create a window company based on offering the highest level of quality and service. With the help of his two sons, Patrick & Jack and backed up by a highly skilled team of craftsman London Box Sash has grown into London’s leading premium window and door manufacturer. As a family business, we have a deep understanding of manufacturing and installing professionally crafted windows, with a knowledge that is unmatched and truly valued, which helps us to create products that deliver on every level.


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About Us

We’ve been operating a family run business, making windows for satisfied customers, for more than 30 years now. A lot has changed since then, but our mission hasn’t. We believe that good work speaks for itself. That’s why we always aim for the highest quality in our products and in our level of dedicated service. That’s why more than 85% of our business comes from repeat customers or word of mouth. And that’s just how we like it.

Read what some of our happy customers have to say about us here

Sash Windows and Beyond

It’s in our name, it’s our flagship product and it’s what we’re known for. But it’s not all we do. Have a look at our main products listed below, or get in touch to discuss any project you’ve got planned.

Sash Windows

The ’50-Year Window’ is our premium option. With longevity and performance being the key factors, we combine traditional joinery methods with high performance double-glazing, draught sealing and the finest quality low maintenance micro-porous paint system, ensuring optimum durability.

Casement Windows

Years of customer collaboration and advances in technology have helped us develop our bespoke 50-Year casement window into one of the highest performing on the market. While we wanted to make our windows thermally efficient, we also wanted to stay true to the heritage of the casement window.

French Doors

Our French doors have been designed to exceed industry standards in performance, insulation, security and finish whilst maintaining their original features. The range is fully bespoke and can be customised to suit your requirements, with the option of different moulding and glazing bar configuration.

Strength, Durability & Quality

We set out to produce quality windows look good, feel good and last. And after years of development and research, we’ve got the perfect formula and we’re happy to present to you the result of our work – the premium 50-year window.


We make 95% of our casement and sash windows using premium Accoya wood. Accoya is an advanced form of timber, modified through a process called acetylation that massively increases its overall strength and durability, matching and even exceeding top-end tropical hard woods. Accoya is created from high quality, sustainably sourced wood.

Design & Finish

Materials are hugely important, but they’re nothing if you don’t use them properly. We’ve been honing our craft ever since we started all those years ago, and our dedication and attention to detail shows in our products. Whether it’s the traditional joints and details or the premium latches and locks, every bit of every one of our windows is carefully considered and adds to their aesthetic and functional quality. We finish our windows using Teknos microporous paint systems; this means long lasting low-maintenance coats.

Area’s We Cover

Although we can supply and deliver nation wide our installers mainly operate within London, Surrey, Kent, Essex and the surrounding areas. We have completed hundreds of projects in the following areas; Wimbledon, Raynes Park, Putney, Clapham, Fulham, Kingston, Richmond, Twickenham, Dulwich, Wandsworth, Kensington, Chiswick, Esher, Hampton Court, Surbiton, Guildford. Give us a call anyway if you are located outside of these areas and we will do our best to accommodate your requirements.