About Us

North London Box Sash is an established company that specialises in the manufacturing and installation of timber period box sash windows, casement windows, and external doors in North London and its surrounding areas.

Mark Bye
Director & Founder, North London Box Sash

We have been in the business since 2000 and have built a reputation for providing high-quality products and exceptional customer service.
Our team of experts takes pride in every project we undertake, ensuring that each client is satisfied with the end result. As the director and founder of North London Box Sash, my goal is to continue providing top-notch services to our clients across London.

My journey in the industry started when I was taken on as an apprentice in Stamford Hill as a glass cutter and glazier. I was passionate about learning the trade and in a few years, I had mastered it. Unfortunately, the company I worked for closed down, leaving me uncertain about my future. However, two carpenters who owned a carpentry business and operated from a glass shop in Tottenham took me on as their apprentice. This opportunity allowed me to broaden my skills and knowledge in the industry and eventually led to the establishment of North London Box Sash.

As a carpenter, I began my career gaining experience by working for various companies in the industry. My skills and dedication were soon noticed, and I was given the opportunity to work on more challenging projects. I was entrusted with a van, which allowed me to carry out surveys, organise materials, and complete carpentry projects on-site.

After many years of working for others, I decided it was time to move on and start my own business. In 2001, I took the plunge and created Supreme Carpentry. My focus was on providing high-quality workmanship in sash windows, doors, stairs, and flooring. I was known for my meticulous attention to detail in oak woodwork.

My company quickly gained a reputation for excellence in the industry. I became a specialist in North London Box Sash windows, which are known for their elegant design and durability. My team and I worked closely with clients to create bespoke designs that complemented the style of their homes.

Over the course of ten years, my company grew into a successful enterprise. My reputation for exceptional workmanship and customer service meant that my details were constantly passed from customer to customer. As a result, advertising was no longer necessary to attract new business.

Here at North London Box Sash we take enormous pride in our ability to provide excellent customer service, from the initial consultation to the final installation. Our team of experts will guide you through every step of the process, ensuring that you are informed and confident in your decision-making. We believe that transparency is crucial when it comes to delivering outstanding services, which is why we keep our clients informed throughout the project.

We understand that every home is unique and requires personalised attention when it comes to its windows and doors. Our team of skilled craftsmen creates bespoke products that are tailored to meet the specific needs of our clients. We use only the highest quality materials, and our products are designed to last for many years, providing excellent value for money.

Meet The Team

At North London Box Sash, the team understands that every client's needs are unique. They take the time to listen to their clients' requirements and provide tailored solutions that meet their specific needs. They also offer expert advice and guidance to help their clients make informed decisions about their projects.

The team is not only skilled in their craft but also friendly and approachable. They understand that home improvement projects can be stressful, and they go out of their way to make the process as smooth and hassle-free as possible. They keep their clients informed throughout every stage of the project, from the initial consultation to the final installation, ensuring that there are no surprises along the way.


Company Director / Founder


Sales Manager


Surveyor and installation team Manager


Installation Team


Installation team


Installation team


Secretary and Accounts

Our Process

Each bespoke window and door goes through a meticulous process for start to finish, ensuring all aspects of the final product is finished to perfection.

Why Choose Us?‍

Our knowledge of over 30 years working with Victorian and Edwardian box sash windows, casement windows & external doors gives us supreme confidence you will be satisfied with our outstanding workmanship and the materials that we use.

Over 30 Years of
Knowledge & Experience
Fully Accredited
Individually Hand-Crafted Windows & Doors
Every Detail of Existing Windows Can Be Replicated
Free Home
Surveys & Quotation
Full 7-Year
Comprehensive Guarantee 
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