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[15] The London Jewel Box Infill on 424 m² with 73.73% coverage and 0% overspend
Map data: Google - Image: Landsat / Copernicus

Location

  • London

Build Start

  • ~2000

Architect

  • Mike Tonkin

Total Floor Area

  • 430 m²
  • [Source: Planning ]
A long, skinny backland plot in North London forced invention, so this “Jewel Box” went heavy on off site fabrication and micro-piles to make a 430 m² live-work home on just 424 m² of land. Site coverage hit 73.73% and the plot ratio topped 101%, yet a fixed-price contract kept the £1.4485m budget locked to the pound with 0% overspend. They bought before consent, leaned on a tight visual brief, and navigated the complexity of custom glazing and glued joints. Bold, intense, and cost controlled, it is a case study in using procurement and method to tame a tricky city plot.

Site Purchase Price

  • £ 427,600

Site Area

  • 424m²

Site Cost Per m²

  • £ 1,010

Initial Budget

  • £ 1,448,500

Total Spend

  • £ 1,448,500

Budget Overspend

  • 0%

Cost Per m²

  • £ 3,369

Site Coverage

  • 73.73%

Plot Ratio

  • 101.53%
All Figures Indexed To
  • 02 May 2025

Construction Type

  • Foundation, Timber Frame

Materials

  • Steel, Wood

Features

A long, skinny backland plot in North London forced invention, so this “Jewel Box” went heavy on off site fabrication and micro-piles to make a 430 m² live-work home on just 424 m² of land. Site coverage hit 73.73% and the plot ratio topped 101%, yet a fixed-price contract kept the £1.4485m budget locked to the pound with 0% overspend. They bought before consent, leaned on a tight visual brief, and navigated the complexity of custom glazing and glued joints. Bold, intense, and cost controlled, it is a case study in using procurement and method to tame a tricky city plot.

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Grand Review

  • 15

Lesson Learned

  • 1
Planning Permission

Always secure planning permission before purchasing land to avoid putting your investment at risk. Understand the local council’s requirements and the likelihood of approval for unconventional designs.

  • Planning Permission, Regulations

Grand Review

  • 15

Lesson Learned

  • 2
Risk Management

Be prepared for risks when engaging in self-build projects, especially in terms of financial investment and timelines. Assess the risks thoroughly and weigh them against the potential benefits.

  • Budget

Grand Review

  • 15

Lesson Learned

  • 3
Innovative Building Techniques

If considering using new or unconventional construction methods, ensure that the builders have experience with them. Verify their capability to handle specialised techniques that may be unfamiliar to them.

  • Challenges, Construction, DIY, Professional, Technology

Grand Review

  • 15

Lesson Learned

  • 4
Detailed Scheduling

Create a detailed timeline that includes buffer time for unexpected delays. Be aware that construction tends to follow a non-linear path and adjustments may be required.

  • Time Management

Grand Review

  • 15

Lesson Learned

  • 5
Clear Communication

Maintain open lines of communication with your architect and contractors. Encourage questions and discussions about the complexities of the build to prevent misunderstandings and mistakes.

  • Working With Others

Grand Review

  • 15

Lesson Learned

  • 6
Documentation Of Changes

Keep detailed records of all changes, discussions, and agreements regarding the build. This can help in resolving disputes and clarifying decisions made during the process.

  • Time Management

Grand Review

  • 15

Lesson Learned

  • 7
Fixed Price Contracts

Consider negotiating fixed-price contracts with builders to protect yourself from potential cost overruns. This can give you financial security during fluctuations in the build process.

  • Budget, Funding

Grand Review

  • 15

Lesson Learned

  • 8
Material Selection

Choose materials thoughtfully, considering not only aesthetics but also durability and function. Understand how different materials perform and their implications for maintenance in the long term.

  • Materials

Grand Review

  • 15

Lesson Learned

  • 9
Design Collaboration

Work closely with your architect to ensure that the design reflects your personal style and functional needs. A good architect should be able to interpret your vision into usable design elements.

  • Design, Working With Others

Grand Review

  • 15

Lesson Learned

  • 10
Weather Considerations

Take into account seasonal weather conditions when planning your build timeline, as rain, cold, or heat can affect laying foundations and other critical tasks.

  • Weather

Grand Review

  • 15

Lesson Learned

  • 11
Understanding Costs

Accept that budgeting for a build may evolve and costs can fluctuate. Regularly communicate about budget expectations and consider all factors that could incur additional expenses.

  • Budget

Grand Review

  • 15

Lesson Learned

  • 12
Personal Attachment

Acknowledge the emotional journey of self-building. The process can be stressful and challenging, but ultimately, it should reflect your vision and values of home.

  • Reflections

Grand Review

  • 15

Lesson Learned

  • 13
Explore Unique Solutions

Don’t hesitate to implement innovative concepts that align with modern standards. Incorporate unique architectural features that resonate with your passions, as these can enhance both the aesthetics and functionality of your home.

  • Challenges, Construction, Design

Grand Review

  • 15

Lesson Learned

  • 14
Quality Over Speed

While it’s tempting to complete the project quickly, Prioritise quality and integrity over a rushed timeline. Poor workmanship or materials due to speed can lead to long-term problems.

  • Budget, Time Management

Grand Review

  • 15

Lesson Learned

  • 15
Interior Design Flexibility

Stay open to changes in design and layout as the build progresses. Flexibility can sometimes lead to improvements that align better with your needs and experiences during construction.

  • Design

Grand Review

  • 15

Lesson Learned

  • 16
Confronting Challenges

Be mentally prepared to face challenges—even crises—and view them as part of the journey. Resilience and a positive attitude can make a significant difference in the outcome and experience of the project.

  • Challenges, Construction, Reflections

Acknowledgment:

This is a non-commercial review carried out for the purposes of study in developing an understanding of the requirements of self-build in the UK.

The views and opinions expressed are my own and is not affiliated in any way with Grand Designs or Channel 4.  All information on this page has been gathered from publicly available sources.

The plot/site information was located using Land Registry and The Department for Levelling Up, Housing & Communities Data which contains public sector information licensed under the Open Government Licence v3.0.

The lessons learned are derived from my interpretations and observations of a publicly disseminated case study and are in no way meant to be a substitute to the original.

Click here to view the original case study on the Channel 4 website.

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