🏡 House Extensions Design Guide (UK 2025)
By Kieran Atherton
Director of Melrose Designs — specialists in home extension plans, Building Regulations drawings, and planning applications across Wigan, St Helens, Warrington, and the North West.
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🧱 Introduction: How to Design the Perfect House Extension
Thinking about extending your home? Whether it’s a rear extension for a larger kitchen, a loft conversion for extra bedrooms, or a side extension to make more living space, extending your property can be a smarter, more cost-effective solution than moving house.
However, success depends on more than just design, you need to navigate planning permission, building regulations, and local design guidance.
This guide explains everything you need to know to plan your home extension with confidence.
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📑 Pillar Page: Your Complete Guide to Home Extensions
This article forms part of our Home Extensions Design Series, a comprehensive resource for homeowners planning to build in the North West.
Explore related topics:
Planning Permission Guide for House Extensions
Building Regulations Requirements for Extensions
Extension Cost Guide – How Much Does It Really Cost to Extend Your Home?
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🧾 Do You Need Planning Permission?
One of the first things to determine is whether your extension falls under Permitted Development Rights or needs planning permission.
✅ Permitted Development
Some smaller extensions — like single-storey rear extensions within specific size limits — can be built without full planning permission, provided they meet national and local criteria.
However, restrictions apply on height, materials, and proximity to boundaries.
⚠️ Prior Approval
Even if your project qualifies under Permitted Development, Prior Approval from your local council may still be needed.
For example, if you’re building near a boundary or significantly altering your home’s appearance.
🏛️ Local Guidance
Always check with your local planning authority (e.g., Wigan Council’s planning portal) or a professional designer before starting.
Melrose Designs regularly liaises with councils to confirm your project’s compliance before submitting any applications.
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🎯 Aims of This Design Guide
This guide helps you:
1. Clarify UK planning policies under the National Planning Policy Framework (NPPF) and Wigan Local Plan.
2. Promote high-quality design that enhances your home and fits with its surroundings.
3. Improve the quality of submissions to speed up planning approval and reduce costly revisions.
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🏠 General Design Principles for House Extensions
When planning your home extension, good design is essential.
Follow these professional guidelines to ensure your project looks great, functions well, and secures approval quickly.
1. Siting
Your extension should complement the existing property and respect the character of the street.
Avoid overshadowing or over-dominating neighbouring homes.
2. Built Form and Scale
Keep the new build subordinate to the main house. Roof pitch, height, and proportions should align with the existing structure.
3. Architectural Details
Reflect your home’s original features — e.g., matching brickwork, windows, and roof materials.
Consistency creates a professional, integrated look.
4. Windows & Doors
Position new openings to protect privacy and maintain good daylight for both you and your neighbours.
5. Materials & Finishes
Use materials that match or complement your existing house. This is a key planning requirement in most UK councils.
6. Accessibility
Consider accessible layouts and entrances for future-proofing, without compromising design quality.
7. Landscaping & Boundaries
Retain green space, add planting where possible, and ensure fences or walls don’t negatively impact neighbouring views or privacy.
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🏗️ Common Types of House Extensions
Extension Type Description Key Design Tip
Rear Extensions Often least visible from the street but affect neighbours’ light and privacy. Keep within the “45-degree rule.”
Side Extensions Can change the street appearance significantly. Maintain spacing between houses.
Corner Plot Extensions Visible from multiple sides. Blend materials and form to suit both elevations.
Loft Conversions / Dormers Add value without using garden space. Match roof style and materials.
Garage Conversions / Outbuildings Ideal for offices or gyms. Maintain harmony with the main house.
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🕍 Listed Buildings & Conservation Areas
If your property is listed or within a Conservation Area, special rules apply:
Heritage Assets: Any extension must respect the building’s architectural and historical importance.
Article 4 Directions: These remove Permitted Development rights — meaning you’ll always need planning permission.
Material Sensitivity: Traditional materials such as natural slate, brick, or stone are often required.
Melrose Designs regularly prepares heritage-sensitive designs that balance modern needs with historic context.
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🧰 How to Apply for House Extension Approval (Step-by-Step)
1. Initial Consultation: Discuss ideas and budget with an architectural designer.
2. Measured Survey: Record accurate dimensions of the existing property.
3. Design & Layout: Create concept drawings to visualise your extension.
4. Planning Application: Submit to your local council if required.
5. Building Regulations Drawings: Prepare technical plans for approval and construction.
6. Construction Stage: Work with trusted builders who follow approved plans.
Melrose Designs offers a complete start-to-finish service, handling everything from design to approval.
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🧠 Why Choose Melrose Designs?
🏡 Over a decade of experience in residential extensions and Building Regulations
🧭 Expert knowledge of Wigan Council and North West planning policies
📐 Fast, affordable, and accurate design packages
🤝 Support from initial sketch to final approval
“Our aim is to help homeowners achieve beautiful, practical extensions — designed for comfort, compliance, and value.”
— Kieran Atherton, Director of Melrose Designs
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❓ Frequently Asked Questions
Q1. How big can I extend without planning permission?
Most homes can extend up to 3 m (terrace/semi) or 4 m (detached) under Permitted Development, subject to local rules.
Q2. How much does an extension cost in the North West?
Expect £1,800–£2,400 per m² for a typical single-storey extension.
👉 See our full guide: Extension Cost Breakdown
Q3. How can Melrose Designs help with planning approval?
We handle all drawings, applications, and correspondence — ensuring your design meets both Planning and Building Regulations.
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⭐ Client Review
“Melrose Designs were fantastic from start to finish. They handled my extension design professionally and guided it smoothly through both planning and building stages. Clear, helpful, and reliable, I’d highly recommend them to anyone looking for quality design work”
— Adam Higson, Wigan ★★★★★