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Endorsed by Which? Trusted Traders

Core Sash Windows

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51 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.

51 reviews
Customer Service
Sort by
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
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