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Endorsed by Which? Trusted Traders

Core Sash Windows

Profile thumb corelogo

53 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

What makes our traders different?

Double Glazing; Windows & Doors is an industry that Which? Trusted Traders has a strong focus on reducing consumer detriment in, due to the nature of it's work / audience of customers. Which? Trusted Traders carries out due diligence on all our endorsed businesses, and we want our consumers to continue to make the right choices about the companies they choose to carry out jobs, especially with renewable businesses. We have a useful article to let you know exactly what you can expect from our traders, find it under the 'advice' section of our website. Did you know Which? Trusted Traders work with a number of competent persons schemes to help raise standards within the home improvement and motoring sectors. For more information please check out our relationships page.


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.

How can we be so sure?

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

53 reviews
Customer Service
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Brilliant professional work and very friendly
Customer Service
Throughout the process everyone we met and spoke to were knowledgeable, professional and completed the work to a very high standard. Responsive and friendly from start to finish. The window itself was fitted and finished neatly, work was very tidy and quick, and looks great! Would definitely recommend.
Customer in Greater London Posted on 21/07/2022 , work completed 15/07/2022
Customer Service
I could not have asked for a better outcome when having full box replacements for my sash windows (based in London Fields, Hackney). Work was carried out to a high standard, efficiently and throughout installation the property was kept clean and protected from the risk of dust and potential damage. Special thanks go to Tim and Nicu who were brilliant. I have no hesitation in recommending Core or using them again in the future.
Customer in Greater London Posted on 07/05/2022 , work completed 21/04/2022
Result very good
Customer Service
We used Core Sash Window on 3 separate occasions for a total of 8 windows and we are very satisfied with the end result. Communication was easy and they responded quickly when problems occurred. They do need careful managing.
Customer in Greater London Posted on 15/09/2021 , work completed 04/08/2021
Excellent service
Customer Service
I used Core to replace 2 windows. The quality of the windows is excellent and the carpenters and painter were hard working and competent. They were all pleasant to have around the house and cleaned up perfectly. The company administration is very efficient. I am already looking to get more windows replaced by Core.
Customer in Greater London Posted on 19/07/2021 , work completed 15/07/2021
Excellent work, highly recommended
Customer Service
Core sash windows did an amazing job on replacing my bay windows. Everyone in the team were friendly, efficient and easy to contact. They are such good quality windows and the installers and decorators had great attention to detail. Tim even organised for additional paint to be dropped by for touch ups when I mentioned the room was still being renovated. I’ll be getting them to do all the windows in the flat and have recommended them to friends. Thanks Core!
Luolan in Greater London Posted on 10/03/2021 , work completed 22/02/2021
100% satisfied
Customer Service
Core Sash Windows were recommended to me when I had to have four attic windows replaced. I was very happy with their work so when I decided to have the rest of the windows in the house replaced I asked them to come back. They built and fitted an additional thirteen sash windows and two casements. They were thorough, friendly and helpful throughout. The windows are beautiful, work perfectly and were extremely well finished. The fitters were a pleasure to have in the house and they left everything in excellent condition. I have no hesitation in recommending them.
Customer in Greater London Posted on 17/02/2021 , work completed 15/02/2021
Highly recommended
Customer Service
Core Sash windows replaced the sashes in my front-room bay of four windows. I was very pleased with their services. Sean and the team were helpful and realistic throughout, and communication was good as the work progressed. They stuck to their proposed timetable, the team were very careful with the property, protected the rest of the room they were working in and cleaned away each evening. The workmanship was excellent, from the carpentry to the painting. Cost wise they were in line with other quotes, but I'd have no hesitation in recommending them given the quality product and the overall service.
Customer in Greater London Posted on 15/02/2021 , work completed 18/12/2020
Incredible workmanship
Customer Service
Having used Core Sash once previously, following much research, for new french doors we didn’t hesitate to use them again to replace old upvc windows at the front of the house with original looking sash windows. From start to finish the whole team were utterly professional. The design matched the original Edwardian windows perfectly. The installers were incredible, meticulous, friendly, they took great pride in their work. They left the site spotlessly clean each day. The attention to detail To the workmanship was second to none. The end result is stunning, we will definitely be using them again.
Customer in Greater London Posted on 23/11/2020 , work completed 21/11/2020
Highly professional, well worth it
Customer Service
Core Sash Windows replaced several old, single-glazed windows in our house with new, double-glazed windows, both sash and casement. The staff were highly professional and considerate about the need to maintain distance from us in the house in the current circumstances. The work was done on the planned schedule and completed to a high standard. We are very pleased with the new windows, which are similar in appearance to the old ones but now the draught has gone and we also notice the sound-proofing is better than before.
Customer in Greater London Posted on 24/10/2020 , work completed 13/10/2020
Highly professional
Customer Service
After having a bad experience with a window replacement some years ago, I was delighted when I found Core. From start to finish they were totally professional and helpful & I am very pleased with the windows & door. I will be using them again in the future.
Customer in Greater London Posted on 06/10/2020 , work completed 19/09/2020