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Endorsed by

Which

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Trusted Traders

Core Sash Windows

Logo on white
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
Profile thumb corelogo

4.6

28 Reviews

About

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

4.6
28 reviews
Customer Service
4.5
Quality
4.6
Value
4.6
Sort by
Exactly what we wanted and extremely professional
Customer Service
Quality
Value
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 London28/07/2019
New french doors
Customer Service
Quality
Value
We were really happy with the service provided throughout. The survey and install team were friendly and polite and everything has been finished to a very good standard. We wouldn’t hesitate to recommend Core Sash to our friends.
Customer in Greater London24/07/2019
Professional outfit delivering a quality product
Customer Service
Quality
Value
I had a new front door made and fitted by Core Sash Windows in June and am very happy with the end product. I'd originally asked them to quote for sash windows over a year ago, so had dealt with some of the staff at that time. Learning from that experience it was important to me to contract a local company this time. I found them professional and helpful to deal with, from the back office all the way through to the workmen installing the end product. The door itself is a quality product which, in my opinion, is good value when I compare it against some other quotes I received. The only area I could pick out for improvement is communication. I found myself calling up or emailing, asking for updates on a few occasions as the lead time was around 12 weeks and installation would likely have been during working time, requiring some planning on my part. Nevertheless customer service gets 4/5, the only area that wasn't 5/5. Happy to recommend Core Sash Windows given my experience.
Customer in Greater London14/07/2019
Installation of new glazed patio doors
Customer Service
Quality
Value
Core Sash Windows installed our new patio doors recently. First class service from start to finish, I can't fault anything. The doors arrived a week earlier than expected, and were installed in 2 days. All work was done carefully and in professional manner, and the end result is great. The doors appear very sturdy and good quality. The installers were friendly and professional and left everything immaculate. They even touched up the paintwork and also recycled the old doors. I would be happy to use Core Sash Windows in future and can recommend their services.
Alexia, Essex24/06/2019
Beautifully finished windows, draft free windows and a pleasure to deal with
Customer Service
Quality
Value
We had the large sash windows on our 2nd floor flat replaced in a conservation area. The windows are absolutely stunning and have transformed the rooms and the level of finish both outside and inside was excellent. I had not realised how much work and what a detailed task the finishing would be to make it good as new. One of the window sills had to be adapted on site around a unit that we had purchased that was bigger than expected, this was done free of charge and very neatly. The rooms are draft free and the windows just slide open so smoothly, I wish I had them replaced before. Every member of the team was helpful and pleasant and responded to questions immediately and Core managed to flex delivery to coincide with other building work. The installers were excellent and carried the huge front window up 2 flights of quite a narrow staircase with no problems - I absolutely would recommend - worth every penny!
Customer in Greater London28/04/2019
Still warm feelings after three years.
Customer Service
Quality
Value
We were having major house renovation works and started off with the windows. All the windows except the sitting room were renewed. The sitting room has the old, interior, wooden shutters and couldn't be replaced with the double glazed units if those were still to work, so these windows were successfully renovated. It was a very happy relationship with Core from start to finish and three years later we are still completely satisfied and happy. The house is warmer and, above all, much quieter. The new sash windows work beautifully. We strongly recommend them.
Willis27/09/2018
Never use this company!
Customer Service
Quality
Value
We have had a terrible experience with Core Sash Windows: they haven't been able to meet the schedule we agreed when placing the order, after weeks we still haven't received the windows we ordered and they keep installing parts that are just temporary solutions. On top of this, no clear communication whatsoever and we are still struggling to get answers and solutions. We strongly advise against using them!
Alessandra27/07/2018
The trader replied (on 05/08/2018)
Hi Alessandra, We understand your frustration and we are very sorry that our efforts to expedite the delivery of your new sashes to receive them in 4 weeks (rather than the standard 8 weeks at this time of year) was unsuccessful. Regrettably, despite the factory operating 2 shifts and working 24/7 in this the busiest time of year, the delivery was delayed which put us and you under time pressure. The delays stemmed from the production of the glass units, so I opted to have the finished sash frames delivered un-glazed and had an extra 10 double glazed units manufactured locally. These were fit in the sash frames so you would have natural light and we replaced them when the correct units were delivered. My thinking was that this option would enable us to fit the windows and finish all interior work by your move-in date of 23/07/18. Trying every available option to avoid an impact on you moving in, was, we felt the right choice when the alternative was to start work a week later on Friday 27/07/18 (by which time all windows had been installed). 1 top sash upstairs is waiting for a glazing unit to be swapped and 2 timber corner pieces to be fitted. Everything else was finished on 01/08/18. My communication in the beginning while I was in constant contact with the factory to find solutions, could have been faster while I was waiting for a confirmed (rather than giving you an estimated) delivery date, I hold my hands up that this should have been communicated to you quicker.
Excellent service and product
Customer Service
Quality
Value
The Core Sash Windows team supplied and fitted two bay windows to our victorian house. Plus casement windows to our loft extension. Last year we had quotes for PVC sash windows and decided wood would be preferable. Core Sash Windows quote was very competitive in comparison. All members of the team were very professional. The fitters and decorators made every effort to minimise disruption to our household. Covering every piece of furniture during the works and thoroughly cleaning up before leaving each day. Everything was sound and secure at the end of each day. We're very happy with the quality and value of the finished product and are very happy to recommend Core Sash windows.
Michael Anthony19/06/2018
Quick installation & great looking results
Customer Service
Quality
Value
Great job on installing windows and door - very efficient all round & making the new kitchen/bathroom look really light, the existing repaired ones feel a lot better insulated too.
rn198024/04/2018
The trader replied (on 05/08/2018)
1
Efficient and stylish double glazed sash windows
Customer Service
Quality
Value
Good standard of workmanship and truly effective and attractive product. My windows were big & draughty, now they are light & stylish and I'm cosy and warm!
Bartholomew04/04/2018
Great work
Customer Service
Quality
Value
The workmanship on a not so simple couple of sash windows is remarkable. the quality of the finished and installed product is excellent.
Christina Z26/03/2018
Excellent job!
Customer Service
Quality
Value
Our windows and door are fantastic, exactly what we wanted. Everybody that we dealt with was excellent -professional, kind and helpful. Core sash windows did a great service and I would definitely recommend them. The quality of the windows and door is really second to none.
Bea Rob24/02/2018
Very happy
Customer Service
Quality
Value
The windows look amazing. I didn't realise how bad they were until they were replaced. Seems like excellent quality and the installation was carried out quickly and efficiently
Whichone123/12/2017
Sash window refurbishment and two windows replaced
Customer Service
Quality
Value
The windows are great, the installation team delivered as agreed, they covered the rooms well to protect from dust and cleaned up after themselves well. The decoration after the windows were installed was of high quality too and it was great to see that there was a team visiting daily during the installation process to check on the work and answer any concerns we had. In particular, Mario was great from when he first came to take final measurements to the end when he made sure our roman blinds were back up properly. We used another company before finding Core Sash Windows and had 1 window and 1 door replaced. Their installation was poor leaving cracks on the outside and they did not restore the inside to the original state. They were also quite a bit more expensive. I'm sorry I didn't find Core Sash Windows earlier, it was such a more pleasant experience. Thank you!
Makeda12/12/2017
Good quality and good workmanship
Customer Service
Quality
Value
Excellent workmanship, nice windows, courteous workers, cleaned up thoroughly. This was done very recently so I can't comment on longevity but the windows look and feel great. I could have used a more detailed description of the windows: I wasn't told about certain details - e.g would I want 'security' knobs, why I wasn't I getting decorative 'horns' on inside? But on the whole really good service ~Many thanks though for a lovely job.
Phyllis Creme07/12/2017
Draught proofing front door
Customer Service
Quality
Value
Very proactive - surveyor turned up on time as did fitter. Extremely tidy job and very effective"
Bridget105607/12/2017
Unfortunately not able to recommend Core Sash Windows – 2 windows they installed 17 months ago have not lasted and now need to be replaced.
Customer Service
Quality
Value
Core replaced 2 small single glazed sash windows in summer 2016, problems arose straight away. Despite 6 attempts to rectify, 10 different people from Core attending, they were unable to resolve to acceptable level. They spent total of 8 days, over a 10 month period working on 2 windows. Some of the issues (too many to list)-initial fitting–left a gap 5 cm wide, 2 mm high, could see straight through to outside. Wood severely splintered in the corner joints, paint on glass, holes in timber, paintwork lumpy, dents in putty. When the second fitter saw the newly fitted windows, they asked me twice if they were the old windows. On another occasion, strips of sealant were left hanging off wood, sashes made screeching noises when opened/closed. Manager did attend once, used his credit card to try & smooth out uneven putty, he admitted putty & paintwork was not good. Within 2 weeks of installation, the putty developed multiple deep cracks, within 2 months it was loose and moved. Core replaced the putty-their attempt was wonky, uneven & lumpy. A few months later, Core returned to paint the putty. Paint started creasing within hours, within days started cracking & flaking off. Their reasoning was that it ‘must have rained and been sunny on the putty’. Paint continues to flake & fall off. Core had the substandard windows made by another company. Core’s manager refused to take responsibility for windows. Ungenerous discount given doesn’t cover distress, upset & major inconvenience caused to me + I will have to pay for new windows.
Anonymous-1516/11/2017
The trader replied (on 11/12/2017)
Dear Anonymous-15 We agree that elements of the finishing by the fitter after Day 1 were in need of improvement, which is why we immediately returned to rectify the issues as soon as you brought them to our attention. As we explained when you decided to go ahead with single glazing replacement, putty will crack as it dries out, but the painted finish will fill these hairline cracks resulting in an unblemished finish. Also as explained, we could not paint the putty until it had fully dried, as putty can dry unpredictably which will affect the painted finish if applied prematurely. Nonetheless, at your request we replaced the putty resulting in further drying time before the windows could be fully finished. As you were dissatisfied with our explanation and resolution, at this stage we were mediating through the Dispute Resolution Ombudsman and Which?, and the discount you received was intended as a gesture of goodwill to repair our business relationship. We subsequently made several attempts to return to your property to paint the putty, as this was the only outstanding issue on the otherwise perfectly functional and finished windows, but unfortunately you did not allow us to do so, resulting in an impasse that we were unable to overcome. We're sorry that you are not entirely happy with the windows you have received, but we feel that we have genuinely done everything within our power during our business relationship. Yours faithfully. Core Sash Windows
Good quality windows and quick installation turn around
Customer Service
Quality
Value
We recently had timber sash windows installed into our property. We ended up going for the basic fit as we were having a number of other work done to the property. This made installation much cheaper and affordable. In comparison the windows were much cheaper that competitors on the market and this was not reflected in the quality as we still got great windows installed. Highly recommended and great service by Dalan Rustemoglu!!!
Halil07/08/2017
Sash window box refurbishment and double glazed sashes installed to the front.
Customer Service
Quality
Value
Three years ago Core replaced some sashes and refurbished others on the back of our Victorian terrace. We also had replicated French doors and a back door replaced. I had no hesitation in asking Core to return for the front window. The information given was clear and no pressure or exaggerated promises were made. Core is able to offer a variety of options e.g. repair and refurbishment and replacement which is helpful if you value original features. I like the open accounting system and the option of insurance for the initial deposit. Financial arrangements were therefore straightforward and reliable. The team as before were professional, punctual, polite and honest and tidied up each day. The finish is excellent and being able to open and air the house more easily is wonderful. Both Daniel and Sean made sure to check that there were no issues. I am very happy and have recommended the company to a neighbour.
Ritten27/07/2017
A less than satisfying experience - delays, incorrect charges and recurring issues
Customer Service
Quality
Value
It started well, though there were delays and prices seemed on the high side. The team were competent and largely efficient regarding the windows though left the paper on one set of sash cords. The two doors and managements response were a tale of misleading pricing, leading to initial overcharging and lengthy delays because there was, it appears, a lack of internal communication within Core. The new basement door fitted well, but it took months to get the right colour hinges. The front door was much bigger negative issue. There were months of delays as a complaint to the original contact at Core was seemingly never passed on. The workmanship left paint bubbling, this was repaired but then bubbled up again. I was also, more seriously, but not clearly indicated on the estimate, charged for a full door refurbishment. I challenged this repeatedly and was only acknowledged as correct after repeated emails despite a full invoice requested - the discount for the one sided treatment, especially given the faulty workmanship was not generous and the door still required attention. Most of these issues could have been mitigated by more efficient customer service and better internal communications at Core and a better attempt at recognising poor customer management and service
Anonymous19/04/2017
The trader replied (on 26/04/2017)
Hi Anonymous, Thanks for your feedback, and we apologise that you aren't entirely satisfied by your experience with Core. You've highlighted that many of these issues were either caused, or exacerbated, by poor internal communication, which we do acknowledge. Unfortunately, our internal resources have been stretched thin due to our company's rapid growth, but we understand that this is no concern of yours, and we will be improving in-house conditions to ensure that these issues do not arise again in the future. With regards to works carried out on your front door, you were originally over-charged as we had initially been contracted for a more comprehensive service than you were after, which we appreciate you have said was due to unclear indication on the estimate. This issue was then further compounded by our painter not informing us that he had performed the door repairs in line with your specific requests, as opposed to your accepted quotation, meaning that our office staff were unaware that you had received a downgraded service and therefore did not lower your price accordingly. Whilst there is no excuse for the poor internal communication, we would like to make it clear that the price you had originally was never intended to reflect the works you ultimately had performed on your door, and that these issues arose from miscommunication as opposed to malice. Kindest regards, Core Sash Windows
High Spec and Stylish Workmanship
Customer Service
Quality
Value
I had researched the well known window and door manufacturers, but Core easily came out tops as they offered the most comprehensive service. The price is also reasonable given the outstanding care and workmanship. Ryan and Marco were full of tips and not pushy as this company has no need to be. Core produced a new front door for my Victorian terrace with a style in keeping with the era, though I chose a colour with a modern edge which compliments the front of my house brightening the exterior and interior. There are a large range of colours to choose from so you can create a bespoke look. The additional warmth created by the insulated door was immediately noticeable. And now I've commissioned core to replace all the sash windows in my home which will be natural wood inside (for a cottage like effect) and white on the exterior. I don't think other companies can offer that level of individual service.
Alison13/02/2017
Superb professionalism and outstanding quality
Customer Service
Quality
Value
We have been extremely impressed by the level of service and workmanship provided by Core. From the professionalism of the survey to the skill of the workmen involved with the installation and painting of the windows, it was been a flawless process. It may be a bit more expensive than other companies, but it is money well spent with quality that is second to none.
Jon S03/02/2017
Very happy with our new windows!
Customer Service
Quality
Value
Professional, friendly service and excellent workmanship. Reasonably priced, not the cheapest but reliable, clean and trustworthy. Head carpenter Ryan is responsive, helpful and a very nice chap. I wouldn't hesitate to recommend them.
Mrs B, Islington21/11/2016
Very very happy with Core
Customer Service
Quality
Value
I was so nervous about appointing someone to do our windows given some of the horror stories you here. However, I couldn't have been happier with Core. They are excellent quality windows, the builders always arrived on time and cleaned up after themselves. The communication and service with their office was always spot on. Payments were easy to keep track of and make through their customer site. And it makes the house so much warmer too - such a noticeable difference. Very happy to recommend to all.
Vicky V09/11/2016
Fantastic work
Customer Service
Quality
Value
excellent workmanship, amazing cleanliness and finishing off that goes beyond expectation - and great windows!
Which? Trusted Traders Consumer04/08/2016
Fantastic Company
Customer Service
Quality
Value
Excellent service and workmanship. Everyone we have dealt with have been fantastic, especially the fitters whom we're friendly, passionate and extremely diligent. I heavily researched the market and found that Core were the only company to offer a comprehensive service. In that they were willing to undertake the minor building work (repointing and plastering), as well as redecorating that results from the replacement of the windows.
stewlauder04/08/2016
High Standards of Workmanship and Materials
Customer Service
Quality
Value
Ours is a typical London Victorian terraced house. After much research and a recommendation from neighbours, we chose Core to replace the windows in our lounge and three bedrooms, and draft proof and re-glaze the front door. From the outset (the initial contact and site survey) it was clear that this was a company that prided itself on a first class product (their website is also very comprehensive) and the quality of its workmanship. The quote was competitive and a start date was agreed. It was to take ten days. At the end of the first week I emailed Core's management and included the following.... Just to say how impressed we are by your team - skilled, diligent, respectful, hardworking, conscientious, cheerful... The superlatives were fully justified and, as the work progressed, it was obvious that the box of each window was being completely refurbished and, with the new windows installed, they would have been fully restored. Neighbours began to notice and ask after the process. On completion, we were assured that 'if any problems arise...' they would be remedied and we were provided with a written guarantee. Put simply, the investment was very worthwhile, the quality of finish was of the highest standard and I can recommend Core to you without hesitation.
Which? Trusted Traders Consumer03/08/2016
Which? Local Review
Customer Service
Quality
Value
We were absolutely delighted with the quality of the work carried out by Core - both double glazing and draught proofing. We immediately felt confident with Sean when he came to give us an estimate. He gave a very clear explanation of the options and the relative benefits, all without any sales pressure. The work was then carried out with huge professionalism and dedication and with great attention to detail.The quality of the joinery and of the painting on our new double glazed windows was staggeringly good. And they cleared up so you would't know they had been ! We got a number of quotes including from the major 'known' companies. We felt Core was the best option in every sense having checked exactly what was included in each quote. We were right and would highly recommend Core for the quality of the work and the value for money.
Adrian Paterson08/06/2013