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We understand that time is of utmost importance to our clients. Therefore, we have designed a ‘quick quote’ estimating page to help our clients receive a provisional estimate for their projects in super quick time. 
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Specialists in period double-glazed timber windows & doors
Transform the look & energy efficiency of your home

Extensive comprehensive guarantees
FENSA & Installsure Accredited
Free next day home surveys
We will not be beaten on price

Save on Energy Bills With Double Glazed Sash window Installation

Welcome to North London Box Sash, we are a company that specialises in period box sash windows, casement windows and doors. Established in 2000, we pride ourselves on our quality product manufacturing and installation all over London and the surrounding areas. Specialising in Victorian and Edwardian period style joinery, we replicate ‘like for like’ timber window and door replacements, all of which conform to current building regulations.

We provide a timeless, elegant and sophisticated finish to all our sash windows using traditional methods and craftsmanship. The North London Box Sash joinery team create bespoke vertical sliding sash windows to match the original design, and retain the period characteristics of your home. Our windows are finished with a heritage draught proofing system which overcomes the age-old problem of cold draughts often associated with sliding sashes. Hand manufactured and installed to maximise heat retention, you’ll have the peace of mind that your home will be warmer in harsh winter conditions, with the additional benefits of acoustic values and thermal insulation. 

We believe that character windows are a very important feature within period houses, and that they must be totally in keeping with the architectural style of the building to ensure that they enhance both the look and the value of your home. Our knowledge of over 20 years working with Victorian and Edwardian box sash windows gives us supreme confidence that you will be satisfied with our outstanding workmanship and the materials that we use in the construction and installation of our windows and doors. You can see samples of our windows on the Window Gallery page and on the News/Projects page, both of which include a selection of our recent sash window installations across North London.

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 

Our Services

Upgrade your home with beautiful,
energy-efficient Sash Windows & Doors

Are you tired of feeling the chill in your home during winter? Are you looking to enhance the visual appeal of your property whilst also enjoying additional benefits?

Did you know that on average, a single-glazed house can lose up to 75% of its heat through windows and doors? That's a lot of wasted energy and money spent on heating. 
Our double-glazed products use the latest technology in glass, timber, and draught exclusion to create an unrivalled product that will keep your home warm and cosy all year round. 

Replacing Sash Windows
in a Conservation Area

While living in a conservation area does not mean that you cannot make any changes to your property, you will have to be more cautious in your approach. Any changes that you wish to make will have to comply with the conservation area regulations, which are designed to protect the character and appearance of the area.

The City of London has 72 conservation areas which are areas of special architectural and historic interest. A conservation area is a heritage asset in its own right, it ensures that the area as a whole, is defined as having special interest as well as its individual features. One of the most noticeable changes you could make to a property is to remove the rich Edwardian and Victorian heritage joinery, including windows and doors. Our experienced team at North London Box Sash can provide a detailed and meticulous initial survey of your property, every detail will be noted and explained, giving you peace of mind you are in great hands and the right choices are made.  

Our approach is to replace windows and doors with ones that match the existing ‘like for like’. This means that we look for materials, colours, and designs that are consistent with the building’s original features. The key to a successful replacement is to ensure that the appearance of the building and the surrounding area is not compromised.

Areas we Cover

We cover the whole of North London and surrounding areas, providing bespoke solutions that meet modern building regulations for energy efficiency while still maintaining the style of your property.

Expertly crafted windows and doors
that retain your home's period charm

Our experienced team specialises in creating beautiful, bespoke timber windows and doors that complement the unique style of your home. We use traditional techniques to replicate the look and feel of Victorian and Edwardian joinery, while also ensuring our products meet modern building regulations for thermal efficiency and noise reduction. Trust us to add value and comfort to your character property.

Take a quick look at one of our completed installations


I recommend North London Box Sash without reservation. Mark is experienced and knowledgeable and is someone who takes a pride in his work. He and his team were polite and efficient and did an excellent job replacing our old sashes with double glazed ones. The work was carried out with fine attention to detail and care for the existing Victorian features. It has also made a big difference to our comfort. I used 2 companies to do the work on our windows but without doubt would only use NLBS if I were to have the work done again”

Roger Cauthery
Inderwick Rd N8 9JY

Mark did a great job for us. Replacing our window was a lot of work, but he arranged everything for us. He used quality materials and the result looks excellent – it’s transformed the whole room.”

Michael Halsworth
Seaford Road N15 5DU

I have used Mark and his team twice now as I was very impressed with initial large box sash fittings, especially the quality of the windows provided, the attention to detail and professional finish of the work, as well as being competitive on price. The work was well organized and completed in a single day on both occasions with my property left in a clean and tidy state. Adding double glazed windows throughout the property has made a huge difference. I would highly recommend the company to anyone.”

Jerome and Elena
Milton Grove, N16 8QY

We’re very happy with our new windows. We considered a number of options, and North London Box Sash gave a competitive quote for a good quality set of windows. We now have lovely double glazed draught-free sash windows, which also block out the noise from the road. I would recommend Mark and his team.”

Aditi Mene
Muswell Hill Place, N10 3RP

I was very impressed with Mark and North London Box Sash from the outset. Mark was incredibly professional from start to finish. He gave a clear and competitive quote, and was able to schedule in the start of works very quickly. The Team that worked on the windows were very competent, polite and friendly. They worked at speed, but at the end of each day always left the rooms they were working in tidy and clean. This was very important for us, as we have two young boys so wanted the least upheaval while the works were going on, as well as a safe environment. The window frames themselves were of very high quality and have transformed the facade of our house. We are delighted with the finished product and cannot recommend Mark and his team highly enough”

Sophie Spinoza
The Crest N13 5JT

Mark at North London Box Sash was very helpful in describing the various options. On the day of the work, he and his colleagues were prompt, tidy and left us with excellent products – draft proof windows in one room, and a new double glazed window in another. Ian the painter arrived a few days later and we now have a fine looking new window, and much warmer, quieter rooms”

Megan Davies
Hardwick Rd N13 4SG

I have been really impressed by Mark and his company’s management of replacing my living room sash windows. Everything was dealt with in a straight forward, knowledgeable and helpful manner and most importantly the windows look great and have made such a huge difference. I was equally impressed with the painting of the window and the re decorating/touch up of the room. I would be happy to recommend Mark and his company’s work and should I need any further work done on the rest of my property will know who to call.”

Jo Redfurn
Albert Rd, N22 7AH

We would highly recommend North London Box Sash. Mark and his team did an excellent job replacing our old sash windows. The results are better than expected. The new windows have made a real difference to insulation and have significantly reduced the noise from the busy road we live on. We are very happy with the work carried out and the efficiency and professionalism of Mark and his team.”

Joanna & Peter Bennett
Page Green Terrace, N15 4NU

I have used Mark and his team twice now as I was very impressed with initial large box sash fittings, especially the quality of the windows provided, the attention to detail and professional finish of the work, as well as being competitive on price. The work was well organized and completed in a single day on both occasions with my property left in a clean and tidy state. Adding double glazed windows throughout the property has made a huge difference. I would highly recommend the company to anyone.”

Jerome and Elena
Milton Grove, N16 8QY

I used North London Box Sash to replace existing double windows which were faced with some very old fashioned and inferior secondary glazing. Mark and his team were quick and efficient, moving things out of the way, covering surfaces with dust sheets, removing rubbish and putting everything back in place afterwards. I was very pleased with the finished work and, now that colder weather has arrived, the new windows seem to be doing the job of keeping me warm.”

Ann S
Dukes Avenue, N10 2PU

After a bad experience with another company we came across Mark at North London Box Sash. He was very polite and knowledgeable. He answered all of our questions thoroughly and put our minds at ease from day one. Mark reconditioned and double glazed around 11 of our sash windows which were in a bad state and they all look brand new now and it has made a remarkable difference. The house is a lot warmer and the windows are now easy to open and close. Mark and his team worked efficiently and tidied up at the end of the day. We have recommended him to many of our friends who have also been very happy with him. Thank you again and we are so glad we found you!”

Eileen Hewett
Osbaldeston Rd, N16 6NJ

We have been very pleased with our new windows. Mark and his team have been very professional throughout. Mark was well informed about all the period details and constructed the windows to a high standard of craftsmanship. When putting the windows in – Mark and his team were very courteous and professional and delivered bang on time. I would have no hesitation in recommending Mark and indeed using him again for other windows and door replacements.”

Giovanna and David Newson
Radcliffe Rd, N21 7SD

North London Box Sash have changed all the windows in my Victorian property.‍Throughout the process i.e. estimate, measuring and commencing the work Mark arrived/started at the agreed times. Mark’s team were professional and took great care with their work, cleaning before leaving each evening. The windows are exact replicas of those removed. I would recommend this company to anyone thinking of replacing their Windows.”

Joyce Collison
Church Hill, N21 1LS

Mark replaced four windows in our Edwardian house and renovated a number of others. Previous owners had taken out the original sashes and replaced them with hideous louver windows. Mark restored the original sash windows to match those downstairs. He didn’t cut any corners, but replicated exactly the original curve on the top panes. He offered a very efficient service in an extremely courteous manner, as did all his workmen. He was very clear as to costs. All the team were very pleasant and did their utmost to keep the mess to a minimum. I would have no hesitation in recommending Mark.”

Angela and Evelyn
Linzee Rd, N8 7RE

Mark and his team came to restore, draught proof some of our sash windows and replace some sills. They were extremely efficient, tidy and actually finished ahead of schedule, the quality of work is great, delivering exactly what they had promised. Mark and his team provide a great service in a timely fashion, I would not hesitate to work with him again.”

Ray Loke
Old Park Road, N13 4RG
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