Planning a house extension in London? Explore practical advice on costs, planning permission, design, Building Regulations and suitable extension professionals.
Planning a
House Extension
in London?
Practical guidance, realistic advice and access to carefully selected, verified extension professionals.
Start Your Extension Project with the Right Information
Planning a house extension can feel overwhelming at first. Before you approach builders or commit to a design, it helps to understand what may be possible, the approvals you are likely to need and the professionals who may be involved.
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APN Extensions provides practical guidance for homeowners planning extensions across London and the Home Counties. Whether you are exploring an early idea, preparing for planning permission or already looking for quotations, our aim is to help you take the next step with greater confidence.
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Where appropriate, we can also introduce you to suitable extension professionals through the Architectural Partner Network.
Where Are You in the Extension Process?
Every homeowner starts from a different point.
Choose the stage that best reflects where you are now.
Explore Different Types of House Extension
The right extension depends on your property, the available space, your budget and how you want to use your home. Explore some of the most common options for London properties.
How a House Extension Project Usually Works
Every project is different, but most successful extensions move through a series of clear stages. Understanding these early can save time, reduce uncertainty and help you budget more accurately.
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Step 1 - Feasibility and Initial Advice
Consider the property, the available space, likely planning constraints and the type of extension that may suit your needs.
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Step 2 - Design and Planning
Prepare a considered layout and determine whether the work requires planning permission, prior approval or can proceed under permitted development rights.
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Step 3 - Technical Design / Build Regs Drawings & Structural Design
Develop the Building Regulations drawings, structural calculations and other technical information required before construction begins.
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Step 4 - Compare Quotations
Approach suitable contractors with a clear scope of works so that quotations can be compared on a more consistent basis.
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Step 5 - Build with the Right Support
Coordinate the contractor and any additional specialists required for the project.
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APN Extensions can help you understand the route ahead and identify suitable professionals at each stage.
How Much Does a House Extension Cost?
The cost of a house extension depends on much more than the floor area alone. Property type, access, structural work, glazing, finishes, kitchen specification, heating, drainage and professional fees can all affect the final budget.
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Online cost-per-square-metre figures can be useful as an early guide, but they rarely tell the whole story. A realistic budget should also allow for the services and decisions that sit around the building work.
Get Better Quotations by Planning Properly First
It is tempting to approach builders as soon as you decide that you want an extension. However, quotations are far more useful when the project has been properly considered and each contractor is pricing the same scope of work.
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Clear drawings, a realistic specification and an understanding of the technical requirements can help you:
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compare quotations more accurately;
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identify what has and has not been included;
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reduce expensive assumptions;
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avoid major surprises during construction;
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decide whether selected elements should be quoted separately.
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The cheapest quotation is not always the best value. The aim is to understand what you are comparing before you commit.
An Extension Usually Involves More Than a Builder
Depending on the project, you may need support from several professionals before and during the build. APN Extensions helps homeowners understand what may be required and, where appropriate, request introductions to suitable specialists.
Extension Advice for London Homes
London properties often present their own set of opportunities and constraints. Terraced houses, side returns, narrow access routes, conservation areas, party wall matters, drainage issues and neighbouring properties can all affect the most suitable route.
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APN Extensions has been created by practising residential design and planning professionals with decades of experience helping homeowners navigate extension projects across London and the Home Counties.
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Our aim is to provide clear, useful guidance before important decisions are made.
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Local area links:​
House Extensions in Bromley →
House Extensions in Greenwich →
House Extensions in Dulwich →
House Extensions in Croydon →
House Extensions in Richmond →
House Extensions in Wandsworth →
House Extensions in Ealing →
House Extensions in Hammersmith →
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Take the Next Step with Greater Confidence
A successful extension starts with a clear understanding of the property, the process and the professionals you may need.
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Tell us about your project and the stage you have reached. We will help you identify the most suitable route and, where appropriate, connect you with suitable extension professionals through the Architectural Partner Network.