The Federation of Master Builders

Cox Format Developments Ltd

Cox Format Developments Ltd, Barnet, Hertfordshire, EN5 5SZ


224a High Street,


Tel: 02084499697
Mobile: 07743373861
Contact: Email us

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Testimonials rating

Member details

Joined: 01/12/1998


Cox Format Developments Limited is a professional building company working within parts of north London and Hertfordshire specialising in Loft Conversions and Extensions with the majority of our work coming through personal recommendations.

We pride ourselves on quoting a good price and sticking to it. Because we are professionals we can see what work is necessary to achieve your objectives and we price accordingly.

We can offer you a full planning service project management and where required structural advise and local authority permissions.

Cox Format have been helping clients maximise the use of there Loft and garden space for over 44 years.

Testimonials (2 testimonials)

Loft Conversion, Rear extension and complete refurbishment of the entire house.


Dear Peter We just wanted to thank you for all the hard work your guys have put into our project. The work was done to a very high standard and we are thrilled with the outcome. James, Graham & Mark’s inputs were invaluable to this project. Mark has given consistent support from beginning to the end - his professionalism was one of the main reasons for choosing Cox Format as our contractor. His promptness in dealing with issues was second to none. Both Graham & James exceeded our expectation as foremen. Their managerial & organisational skills on top of their craftsmanship were the catalyst for the success of our project. Also Graham’s carpentry skills are superb, which must be a real asset to your company. Thank you again for all your support for the past 5 months. All the best, James & Yoko

Porch, GarageConversion & Side Extension in Barnet EN5


The whole project ran like a military operation and if things fell behind due to unforeseen circumstances Cox Format caught up with things by sending in reinforcements. There were regular site visits by the Managers and constant feed back. We received helpful advice throughout. We were very pleased with the work which was finished to a high standard and on time and all of the workmen were very obliging. Danny

Case Studies


Loft Conversion - North London, Southgate N14


This property is a large Edwardian style terraced house in the sought after area of Southgate, North London N14. Our brief wasto convert the existing loft space and build a large loft room to be used as a light and airy hobby room. We built a separate bathroom over the back addition of the house. The owners invested in their property rather than move and a loft conversion certainly adds immediate value to your property rather than spending it on stamp duty and removals! Party walls and building work. We helped the owners with their Party Wall documentation and internal designs. Our approach is to involve the client at every step of the build so that every opportunity to maximise space is considered. We’re happy to be flexible and ensure our clients get value for money and a space they are 100% happy with. We’ were also asked to renew the roof, and to re-align all the existing gutters, fascias, soffits and downpipes. A large percentage of Cox Format’s work is by referral and word of mouth. Our on-site team are all very polite and neatly turned out and approachable. We’ve had several neighbours and passers-by stop and ask for brochures so we hope to be working in this lovely area again quite soon.


Loft Conversion - High Barnet EN5


This project is for a lovely retired couple who wanted to create more space for visiting grandchildren and at the same time add a substantial amount of value to their property. Theirs is a 3 bedroomed semi-detached property in a sought after road in High Barnet, North London. Cox Format Developments had completed a similar loft conversion project further up the same road and our clients were able to visit this completed loft extension and see EXACTLY how much additional loft space they could achieve in their own home. We find that our clients are happy to share their experience with other prospective clients once a loft is completed but we always seek agreement in advance if clients do ask to see completed projects. In most cases, Cox Format provide an end to end managed design and build service which includes consultations with our in-house architects and dedicated project management throughout the project. Saving clients’ money by combining work on loft conversions We advised our clients on a plumbing and hot water upgrade, bathroom suite selection and tiling as well as lighting plans, all as part of our standard service. They also elected to renew the roof at the same time as the original was nearing its end of life. We provide roof tile samples so that clients can choose exactly what they would like. This typically can save clients between 20-30% of the cost of a new roof if it is done at the same time as a loft conversion. Cox Format’s approach is to do projects WITH our clients rather than TO them; we work in a very flexible way, consulting the client before and during all phases and giving clients’ plenty of notice for decisions that have to be made. We provide brochures, samples and contacts for any needs that our clients may have and we are happy to do the research so that clients have a stress free experience.


Double Hip to Gable Loft Conversion and Rear Extension - Whetsone North London N20


This project involved a large loft and single story rear extension project for a local family in Whetstone North London who need more space. The family approached us on a recommendation from friends who are previous clients of ours. In fact, a large percentage of our business is either repeat or direct recommendation. This family had a strict budget they wanted to work within so we spent extra time with them developing a comprehensive scope of works. They specifically asked us to provide lots of detail to help them with their budgeting as they wanted to avoid any unforeseen costs. We employ a project manager that goes the extra mile for clients and spends time helping with whatever questions they may have. This family’s loft will not only add much needed living and storage space but will increase the value of their home. It’s so much more cost effective to spend money on loft conversions and extensions nowadays, rather than stamp duty and solicitor’s fees that can add up to a significant amount when moving to a new house. Double Hip to Gable Loft Extension We’ve built a double hip to gable loft extension that has provided a large double bedroom, walk-in dressing area, shower room and loads of extra under eaves and under stairs storage space.The client also asked us to renew the roof at the same time which will save them money in the long run as we used the same scaffolding as for the loft. As part of the design and build process that we offer, we worked with the client’s brief for lots of natural light. The loft has two Velux windows, two gable windows giving light to the new stairwell plus bathroom and bedroom windows. There is also the luxury of a walk-in dressing area in front of the shower room and extra storage space under the eaves. This is accessible via low level doors and is boarded and insulated. At ground floor, we’re building a rear extension with large windows, French doors and an aluminium double-glazed roof lantern which provide lots of natural light and make it feel like part of the garden. We spent time sourcing new bricks and windows so that it all matches the existing house. We’ve also built a set of wide, redbrick steps that lead down to a garden music room. Cox Format are a WHICH Trusted Trader and member of the Federation of Master Builders.


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Member type

FMB member with TrustMark

  • Have signed the TrustMark license
  • Have had an inspection on a job in progress on joining and on a completed development every three years thereafter
  • Has a minimum of twelve months trading
  • Verified no un-discharged bankruptcies or relevant and outstanding County Court Judgments
  • Have passed credit checks, public record and director checks
  • Has Public and Employer (if applicable) Liability Insurance
  • VAT registration (if applicable)
  • Confirmation of business address/details
  • Cox Format Developments Ltd has agreed to abide by the FMB Disputes Resolution and Complaints Procedures
  • Has signed up to the FMB Code of Practice
  • Can offer the suite of FMB Insurance warranty products for the domestic and commercial markets (contact the FMB Insurance office for rates)

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