Step-by-Step Guide to Designing a House Extension
10 Dec 2025 • Written By Timothy Metcalfe
A Guide by Forma Architecture
Extending your home is an exciting opportunity to create more space, improve functionality, and add value to your property. At forma architecture, we follow the RIBA Plan of Work, a trusted framework in the UK, to ensure a structured and efficient design process. Whether you're in London, Manchester, or anywhere nationwide, our approach helps you navigate planning, design, and construction with confidence.
Step 1: Preparation & Brief (RIBA Stage 1)
The process begins with understanding your requirements, budget, and aspirations. At this stage, we:
• Discuss your goals and priorities
• Advise on planning feasibility and any constraints
• Recommend a measured survey of your home
• Explore initial ideas for your extension
Step 2: Concept Design (RIBA Stage 2)
With a clear brief, we develop creative design concepts tailored to your needs. This includes:
• Producing sketch designs and 3D visualisations
• Exploring different layout options to optimise space and natural light
• Reviewing planning policies to ensure compliance
• Refining the design based on your feedback
Step 3: Developed Design & Planning Application (RIBA Stage 3)
Once a preferred concept is agreed, we refine it further and prepare for planning submission:
• Develop more detailed architectural drawings
• Incorporate structural and sustainability considerations
• Liaise with planning consultants if necessary
• Submit the planning application and manage council communications
Step 4: Technical Design & Building Regulations (RIBA Stage 4)
After planning approval, the design is developed into a technical package:
• Create detailed construction drawings and specifications
• Coordinate with structural engineers and other consultants
• Submit applications for building regulations approval
• Prepare tender documentation if you are seeking contractor quotes
Step 5: Construction & Project Oversight (RIBA Stages 5-6)
With approvals in place, construction can begin. forma architecture can:
• Assist in selecting a contractor
• Provide site visits and project oversight
• Ensure quality control and adherence to the design
• Help resolve any issues during construction
Step 6: Completion & Handover (RIBA Stage 7)
The final stage ensures everything is completed to a high standard:
• Conduct a final inspection
• Address any snags or minor adjustments
• Provide documentation and maintenance guidance
Thinking About a House Extension?
At forma architecture, we specialise in designing bespoke, high-quality home extensions across the UK. If you're considering extending your home and want expert guidance, book a free 30-minute consultation today. Alternatively, you can get in touch via our contact page, or email us directly at hello@formaarchitecture.co.uk
Why Choose forma Architecture?
✅ Experienced in residential extensions nationwide
✅ Bespoke, client-focused design solutions
✅ Expertise in planning applications and building regulations
✅ Clear and structured process following the RIBA Plan of Work
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Let’s Create Something Exceptional
A well-designed home is an investment in your lifestyle and future. With expert planning, thoughtful design, and efficient execution, we ensure your project meets your vision while staying cost-effective. If you're ready to take the next step, let's discuss your ideas and turn them into reality.
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