Business Details
41 Years
experience
Award-Winning Loft & Extension Builders in North London
Cox Format Developments has been operating for over 35 years, specialising in loft conversions and house extensions across North London and surrounding areas. Our team combines extensive local planning knowledge with a commitment to fixed pricing and transparent project management. We pride ourselves on employing skilled craftsmen directly, ensuring quality control from initial consultation through to completion. Our services include structural advice, planning permissions, and full project management, with a focus on minimising client stress. We guarantee our pricing and workmanship, avoiding hidden extras that often plague the construction industry. With a strong reputation built through personal recommendations and Which?Trusted Trader status, we prioritise customer satisfaction through clear communication and reliable delivery. Our 35-year track record demonstrates expertise in navigating local authority requirements while maintaining high standards of workmanship. We use premium materials to ensure longevity and offer comprehensive warranties for all projects. Our team's apprenticeship-trained professionals deliver tailored solutions for residential properties, focusing on maximising space efficiency. Clients benefit from our local office presence in Barnet and a proven process that balances budgetary constraints with design aspirations.
Services
Loft Conversions
House Extensions
Home Interiors
Planning Services
Structural Advice
Details
- Year established: 1985
Highlights and features
- 35 years of specialist experience in North London property developments
- Fixed pricing with no hidden extras or unexpected charges
- Directly employed craftsmen with apprenticeship training programs
- Comprehensive planning and structural advisory services included
- Which? Trusted Trader status with 100% price and quality guarantees
Associations and certifications
- Which? Trusted Trader
What people say
Stress-free service
On time delivery
No hidden charges
Professional team
High quality finish
Services
Loft Conversions
Specialist loft conversion services transforming unused spaces into functional living areas. Our 35-year expertise includes dormer, hip-to-gable, and mansard conversions with guaranteed pricing. We handle full project management from planning permission through to completion, ensuring compliance with North London building regulations while maximising property value.
House Extensions
Custom house extension solutions including side, rear, and two-storey extensions. Our directly employed craftsmen deliver fixed-price projects with comprehensive structural calculations and planning support. We specialise in seamless integration with existing properties while maintaining minimal disruption to homeowners throughout the construction process.
Home Interiors
Complete interior finishing services complementing structural developments. Our team provides bespoke decoration, kitchen installations, and bathroom renovations using premium materials. We ensure cohesive design integration with converted spaces while maintaining the property's original character and meeting modern living requirements.
Planning Services
End-to-end planning application support including architectural drawings and structural calculations. Our local authority expertise covers permitted developments and complex planning submissions. We manage council communications and party wall agreements to ensure smooth approval processes for loft conversions and extensions.
Structural Advice
Professional structural engineering services integrated with all development projects. Our in-house expertise covers load calculations, material specifications, and compliance certifications. We provide detailed assessments for both new developments and existing property modifications, ensuring safety and regulatory compliance throughout the construction process.
Questions
Do you offer fixed-price contracts for loft conversions?
Yes, we guarantee our initial quotation with no hidden extras. Any additional work requires your explicit approval before commencement.
How long does a typical house extension take?
Most single-storey extensions complete within 12-16 weeks, with larger projects scheduled according to scope. We provide detailed timelines during planning.
Are planning permissions included in your services?
Yes, our team manages full planning applications including architectural drawings, structural calculations, and council submissions as part of our service package.
What areas do you cover for residential projects?
We operate throughout North London including Barnet, Enfield, and Hertfordshire, with a physical office in Barnet for client consultations.
Do you use subcontractors for construction work?
We directly employ most tradespeople, with apprenticeship-trained professionals handling core works. Specialist subcontractors are used only when necessary, maintaining quality control.
What guarantees do you offer for completed projects?
All work comes with comprehensive warranties covering both materials and workmanship, with specific terms detailed in our pre-contract documentation.
