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Endorsed by Which? Trusted Traders

Core Sash Windows

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50 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
  • 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

Why you can trust these reviews

All reviews are verified as being genuine and a true customer of this trader.

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100% of the reviews we publish have been through our stringent moderation process.

50 reviews
Customer Service
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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
Outstanding job - 11 timber double glazed sash windows
Customer Service
My experience with Core Sash Windows was simply outstanding. I had 5 sash windows refurbished, replacing the sashes with double glaze timber panes but retaining the window boxes. I retained an original feature of the house whilst installing double glazing which is infinitely better than full PVC replacement and cheaper than full timber replacement. The workmanship in the refurbishment of the box was remarkable and the new double glazed sashes are probably the best I have come across. I admit they were not cheap but the quality justifies the expense. The job was completed in May and so good that I decided to replace another 6 windows in the house which is also done to the same high standard. I highly recommend Core Windows.
Customer in Greater London Posted on 18/12/2019 , work completed 21/09/2019
Poor workmanship, followed by poor customer service.
Customer Service
Despite confidently assuring us that they would make good and leave no trace, their installers didn't clear up after themselves, leaving rubble and dust on the floor for several days at a time, even when they were applying the top coat of paint (which any good painter will tell you is a cardinal sin!) - and leaving their empty drinks cans lying around. They managed to leave scrapes, scratches and dents on walls and woodwork throughout the house, and made such a bad job of touching up / fixing these issues that they had to come back several times and ended up having to repaint several walls in their entirety. On one occasion I turned up to meet their Director at the house and he was hanging out of the window with a hoover, apparently cleaning the gutter. When I came in, I noticed that he had splattered dirty gutter water across half of the walls... cue another few rounds of touch ups... The windows themselves seem pretty good (they are made by a supplier in Estonia I believe) but the final coat of paint was very messy and left drips running down walls, on the skirting boards, radiators etc., so again this was something they had to come back and fix over several visits. Worst of all is that through all of these issues, their customer service was appalling and made the whole process extremely stressful. From not showing up to meetings, to simply being rude and trying to make excuses for things they were clearly at fault for, and now simply ignoring emails.
Customer in Greater London Posted on 11/11/2019 , work completed 27/09/2019
The trader replied (on 09/12/2019)
We are sorry that your experience could have been better. You notified us that there were some marks upstairs on the newly painted walls of your home. We agreed that we had been responsible for leaving some of the marks during the installation of your Accoya double glazed windows. There was substantial ongoing works taking place throughout the house at this time with multiple trades on site. We suggested we would fully paint all of the walls upstairs so we could leave you with the best possible finish. This was carried out to your satisfaction and we also gave you £200 in John Lewis vouchers for the inconvenience of having our painters for additional days on site. After this you emailed to say that you wanted £1500 compensation before you wrote reviews about us on various sites. We have rectified the issues you brought to our attention. However, we are unable to provide you with any further payments. We regret that we were unable to completely resolve your complaints but we do appreciate your business. We will of course, honour all guarantees and we will return if you have any issues with our windows in the future. Yours sincerely, Sean Mac Anbhaird Managing Director Core Sash Windows
Very professional
Customer Service
We had french doors fitted in our Victorian/Edwardian house. Attention to detail was amazing. The doors look like they’ve always been there except much less draughty and rattling! The service we had from Core was very professional. The doors took a while to make but they are so well made it was worth the wait. We were kept informed of progress at every stage and installation was fast and efficient. The guys on site were very professional - incredibly polite and extremely conscientious. All in all it was a very positive experience. Highly recommend them.
Customer in Greater London Posted on 25/10/2019 , work completed 31/07/2019