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Trusted Traders

Core Sash Windows

Profile thumb corelogo


43 Reviews

Opening Hours
Today - 08:30–17:30
  • Monday 08:30–17:30
  • Tuesday 08:30–17:30
  • Wednesday 08:30–17:30
  • Thursday 08:30–17:30
  • Friday 08:30–17:30
  • Saturday - Closed
  • Sunday - Closed


Core Sash Windows is a London-based double-glazing company specialising in the replacement and repair of traditional timber-framed windows and doors. We understand that replacement windows and doors are an important investment, and you obviously want to make the correct choice.

That is why we offer:

• Elegant and traditionally styled products
• Attentive customer care
• Punctuality and reliability
• Considerate workmanship
• Convenient and fully comprehensive service
• No need for Third Party trades

That is why we promise:

Our surveys are always performed by experienced carpenters instead of designated sales-people - there's no unnecessary up-selling and no high-pressure tactics. Our FENSA-registered installation service also includes the hand painting of your new products, traditional sand-and-cement pointing joints, and the repair of any damaged plaster. And our traditionally designed windows and doors come with a 10 Year Insurance-Backed Guarantee.

What we do

  • Glaziers

    • Sash windows
    • Timber windows
    • Window consultants
    • Replacement window services and repairs
    • Double glazing installation
    • Aluminium Windows
    • Double glazed units
    • Double glazing repair
    • Stained glass
    • UPVC Windows
  • Double glazing

    • Double glazing installation
    • Double glazing suppliers
    • Double glazing repairs
  • Carpenters

    • Joinery and carpentry
  • Doors

    • Bi-fold doors
    • French doors
    • Front door
    • Patio doors
    • Timber doors
    • UPVC doors
    • Orangeries
  • Draughtproofing installers

  • Specialised building trade contractors

  • More Services

    • double glazed timber sash casement windows and doors

Customer reviews

43 reviews
Customer Service
Sort by
Totally happy, highly recommend in all areas, from the product through job execution and service received.
Customer Service
We had all 6 of our Sash windows of various dimensions replaced by Core and we are very happy with them. They all work well and slide up and down like a dream (you don’t need to be a regular gym-goer). Any slight adjustments or easing we required after the work was completed was immediately tended to with no quibbling. Last, but not least, the noise reduction is amazing as is the energy saving. Last winter we used our heating for less than three hours a day and often just an hour in the morning was sufficient to maintain 20-21C. All the windows are made to detailed measurements and all fitted on arrival. We were constricted by Islington Council Conservation requirements and Core were able to work to those detailed restrictions. Core personnel from our initial contact Dalan Rustemoglu (surveyor), through the office staff to the carpenters and painters, were very professional and helpful. We highly recommend them and now at least 10 other friends and neighbours have, on our recommendation and on viewing the windows, purchased Core windows also. No one has any complaints!
Customer in Greater London Posted on 31/08/2020 , work completed 31/10/2019
Excellent service from a top quality company
Customer Service
The guys at Core Sash Windows provide a really excellent service. We have used them on a couple of occasions now and each time they have gone above and beyond our expectations of the service provided. Their product is top quality and the whole process from start to finish is efficient and streamlined. I highly recommend them!
Customer in Greater London Posted on 04/08/2020 , work completed 12/06/2020
Excellent work with tidy & clean approach
Customer Service
We had to replace the top sash of one of our windows. After some research and other good reviews I have seen on Which, I decided to go with Core on this. Their sales team is very helpful, answers all of your questions and pays attention to your needs. The new sash production was on time as promised. The job was scheduled and completed on time as promised. They came in and worked so diligently, when they left, there was not even a single dust in the room. And the window was fitted so nicely and is now operating smoothly. Core has done a great job and if I am ever in need of another sash window work, they will be my go to.
Customer in Greater London Posted on 25/07/2020 , work completed 14/07/2020
Excellent - better than a large competitor
Customer Service
We had 6 sash windows and 1 casement installed in Dec 2019. The installation team arrived on time and were respectful both to us and our property. They kept us informed and cleaned up each day to a reasonable standard. The finish on the windows is fantastic: the final hand coating of paint (by Steven) makes all the difference, and not many companies I had quote offered this. I had previously had 2 sash windows installed by another very large company (LSWC, green logo!) and these windows by Core win hands down - both on appearance, smoothness of operation, and the “making good” of surrounding plasterwork etc. A special shoutout to Steven for that. We did have an issue with on one of the 7 windows we had installed - the architrave used was too large compared to the original and as installed was overlapping the rooms cornicing which spoiled the look of the room. There was a bit of back-and-forth with the company on the matter, necessitating some before and after photos to show the original appearance, but afterwards they did agree to return and fit a smaller architrave at their expense. In an ideal world this would have been picked up by them during the survey and adjustments made ahead of time, but credit to Core, they did return and put it right, so no hard feelings from me and they will be my #1 choice for next time given everything else was top-notch. No experience (yet) of having to call on their warranty.
Customer in Greater London Posted on 10/05/2020 , work completed 11/12/2019
Professional and beautiful
Customer Service
We had new bay and sash windows from Core Sash. All the staff we dealt with were professional and polite. They took care to minimise mess and inconvenience and the finishing off work was excellent. We had to pause work due to a leaky roof and this was accommodated without fuss. The finishing off work breathed new life into our rather worn and old plaster work and ledges.
Customer in Greater London Posted on 24/03/2020 , work completed 23/03/2020
Large window replacements
Customer Service
From initial meeting to survey work, to measurement and logistics, and then installation and cleaning up, Core Sash Windows did a super job. We are delighted with the work, and would have no hesitation in using them again. In fact, we just called to do just that.
Customer in Greater London Posted on 16/01/2020 , work completed 15/01/2020
Fantastic every time!
Customer Service
This is the second time we have employed Core Sash to replace our windows and again they did not let us down. From start to finish they were polite, professional, punctual and helpful. We are delighted with our windows which are beautifully crafted and work very efficiently. They cleaned up constantly throughout works and made good and painted around the windows beyond where they needed.
Customer in Greater London Posted on 15/01/2020 , work completed 22/10/2019
Great quality and customer service
Customer Service
Core sash replaced an original timber sash window for us in our nursery. We were on a tight deadline and they managed to turn everything around for us before Christmas. Customer service was great and we were very impressed with the quality of work and professionalism of the fitters especially, much better than a lot of the tradespeople we used for the house. The finish was great. Expensive but worth the money.
Customer in Greater London Posted on 14/01/2020 , work completed 21/12/2019
Fantastic - highly recommend
Customer Service
The windows look AMAZING and we are very happy. The team we had were brilliant, so tidy and lovely people to have around. Thanks to everyone at Core.
Customer in Greater London Posted on 13/01/2020 , work completed 10/08/2019
Trusted Trader indeed
Customer Service
Core supplied and fitted replacement French windows and frame. First impressions, helpfulness and communication were first rate. We would not hesitate to recommend them.
Customer in Greater London Posted on 23/12/2019 , work completed 20/11/2018