Endorsed by Which?

Core Sash Windows


57 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

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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.

57 reviews
Customer Service
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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
Awful experience!
Customer Service
We recently had four sash windows replaced by Core Sash Windows. They requested 8-10 weeks to make the windows. As we approached ten weeks, they made no effort to contact us to let us know the windows were delayed. After rescheduling to the 13th week, we received a call at 3pm the Friday before they were due to start on Monday to say they didn't have one window and had no idea when they would have it. Once they started the work, they got three days in and then didn't show up for two days. They refused to answer the phone and never provided a credible plan for completing the job. Once complete (finally), they chased us for payment within 24 hours and continued to chase every day with multiple calls and email over the next few days. They are awful to deal with and I wouldn't recommend them to anyone.
Customer in Greater London Posted on 06/10/2019 , work completed 03/06/2019
The trader replied (on 11/11/2019)
We are sorry to hear about your experience. It took us a while to figure out who posted this review. Confusion arose because you were not our direct client. The property management company of your building contracted their builder who in turn contracted us to carry out the window upgrade works in your flat. Our client took some time to decide on several details of the job - whether the sides of the windows should open or not with the Venitian window and whether they wanted a hand painted or spray painted finish. The 8 – 10 week lead-time will only have begun after they clarified these details with us in writing. We provided our client with a ‘Schedule of works’, that outlined the entire work process & they were in contact with our surveyor throughout. However, we understand that this has been frustrating for you and that some information was lost along the way. As a result of your feedback we have made improvements to our systems of communication; particularly when there is a third party involved so that all parties are onboard from the outset.Please get in touch if you would like to discuss this further. We’d appreciate the opportunity to make things right and work towards earning back your business.
Brilliant quality windows fitted by professionals
Customer Service
I recently had 7 one-over-one, top and bottom opening, engineered box sash windows fitted by Core Windows. The original site measuring and ordering process was very smooth with detailed breakdown of each window (materials, window furniture, glass, openings mechanism, cills painting and undercoat systems) which was provided a couple of days after the first visit. I opted for a basic fit as I had builders onsite renovating, and this was carried out to a very highly standard. The windows look amazing and are very solid, with decent weight, smooth opening and cut out a lot of external noise. I’ve already had two neighbours enquire where they are from and whether I’d recommend - in answer to that, I would highly recommend Sean, Tim and the team at Core and would not hesitate to use them again should I need to.
Customer in Greater London Posted on 27/09/2019 , work completed 18/08/2019
Exactly what we wanted and extremely professional
Customer Service
Core made and installed 3 sets of French doors for our Edwardian house. We took ages to decide on a supplier as so many door manufacturers only provide off the shelf products which look cheap and insubstantial. We chose Core because they were prepared to make bespoke doors to our specification at a competitive price. We are delighted with the doors now they're installed. They are beautifully made and finished and the design is completely sympathetic to the age of the house. We had dreaded the fitting process, expecting lots of mess and damage to existing decoration (old doors had to be taken out and new frames installed along with new architrave and skirting). We couldn't have been more wrong - the carpenter and painter were incredibly clean and tidy, clearing up any mess before they left each evening. They were professional, friendly and polite and a real credit to the team. The finish is exceptional - they really went the extra mile to make sure everything was perfect and we were happy. There is no need for any further decorating work - they made good all damage to plaster and trim - you really would not be able to tell that the doors are new. We were so happy with the whole experience. In fact it was so incredibly easy and painless we're thinking of replacing the windows now... Thoroughly recommend them.
Customer in Greater London Posted on 28/07/2019 , work completed 20/07/2019