About APN Extensions
Practical guidance for homeowners planning a house extension
APN Extensions has been created to help homeowners make better-informed decisions before, during and after a house extension project.
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Extending a home can be one of the most rewarding improvements a homeowner makes. A well-designed extension can create a brighter kitchen and dining area, provide space for a growing family, improve the relationship with the garden and add long-term value to the property.
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However, house extensions also involve important decisions.
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How large should the extension be? Do you need planning permission? Would a rear extension, side-return extension or wraparound design work best? What drawings will the builder need? How much should you budget for professional fees, structural work and the less obvious costs that are often overlooked?
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APN Extensions provides clear, practical information to help homeowners understand the process and move forward with greater confidence.
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Built on residential design and planning experience
APN Extensions is part of the Architectural Partner Network (APN), a curated network created by practising residential design and planning professionals.
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The guidance across this website draws on more than 40 years of experience in residential property, building projects, planning matters and pre-build project support across London and the Home Counties.
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We understand house extensions from several different perspectives:
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The homeowner trying to improve a property without wasting money;
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The designer considering layout, appearance and planning constraints;
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The builder preparing to price and deliver the work;
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The specialist professionals needed to support the project;
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The property owner trying to make sensible decisions that will stand the test of time.
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Our objective is not to overcomplicate the process.
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It is to help homeowners understand the options, avoid common mistakes and identify the right next steps for their particular project.
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Explore different types of extension
There is no single extension design that works for every home.
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The best solution will depend on the type of property, the available garden space, the planning constraints, the budget and the way the homeowner intends to use the additional room.
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APN Extensions provides guidance on a wide range of popular project types, including:
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Rear extensions;
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Side-return extensions;
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Wraparound extensions;
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Full-width extensions;
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Double-storey extensions;
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Side extensions;
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Bungalow extensions;
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Kitchen and dining extensions;
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Orangery extensions;
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Conservatory extensions;
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Extensions combined with loft conversions.
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Some homeowners want a large open-plan kitchen and family room. Others need a ground-floor bedroom, a home office, a dining room, a utility area or a semi-independent space for an older relative or teenager.
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A good extension should respond to the household rather than simply add as much floor area as possible.
Understand the complete project
The cost of an extension is not limited to the builder's quotation.
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A properly planned project may involve architectural drawings, planning advice, Building Regulations information, structural calculations, Building Control or a Registered Building Control Approver, party wall matters, drainage considerations, glazing, rooflights, doors, kitchen design, interior finishes and landscaping.
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That does not mean every homeowner needs every service.
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It does mean the project should be considered as a whole before construction begins.
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APN Extensions provides practical articles and guidance covering:
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Planning permission and permitted development;
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Extension design ideas;
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Build costs and professional fees;
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Hidden extras and contingency budgets;
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Builder quotations;
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Building Regulations drawings;
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Structural engineering;
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Party wall matters;
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Building Control;
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Project management;
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Glazing, rooflights and doors;
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Preparing for construction;
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Projects that are already underway.
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The aim is to help homeowners understand what they are likely to need and when they are likely to need it.
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Better information before asking builders to quote
One of the most common mistakes is approaching builders before the design has been properly considered.
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A builder can provide an initial budget indication, but a meaningful quotation usually requires clear information.
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Without drawings and a reasonably defined specification, different builders may make different assumptions. One quotation may include structural steelwork, drainage changes and internal finishes, while another may leave important items out.
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This makes it difficult to compare prices fairly.
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APN Extensions encourages homeowners to think about the layout, planning position, structural requirements and intended finish before committing to construction.
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The objective is not to create unnecessary paperwork. It is to reduce uncertainty and help homeowners obtain more useful quotations.
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Access to suitable professionals
A house extension project often involves more than one professional or contractor.
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Depending on the scope of the work, a homeowner may need support from:
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Extension builders;
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Architectural designers and planning consultants;
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Building Regulations specialists;
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Structural engineers;
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Registered Building Control Approvers;
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Party wall surveyors;
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Project managers;
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Glazing, rooflight and door suppliers;
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Kitchen designers and installers;
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Landscaping and patio specialists.
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Where appropriate, APN Extensions can help connect homeowners with relevant professionals through the Architectural Partner Network.
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APN is not intended to operate as a generic mass lead-selling website.
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The objective is to provide a more considered route for homeowners who need guidance and suitable professional support for a genuine residential project.
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Any introduction is optional. Homeowners remain free to obtain their own quotations and appoint the professionals or contractors they consider most suitable.
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London and the Home Counties
House extension projects vary significantly by location.
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A modest extension to a suburban detached house may raise different issues from a side-return extension to a Victorian terrace in London. Conservation areas, Article 4 Directions, locally listed buildings, restrictive planning conditions, neighbouring properties and access constraints can all influence the design and the construction process.
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APN Extensions has a particular focus on residential projects across London and the Home Counties, including Kent, Surrey, Essex, Hertfordshire, Buckinghamshire, Berkshire and Sussex.
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The general guidance on this website will also be useful to homeowners elsewhere in the UK, although local planning policies and project costs will vary.
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Helping homeowners make sensible decisions
Not every house needs the largest possible extension.
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Sometimes a modest rear extension with a well-planned internal layout will provide better value than a much larger scheme.
Sometimes a side-return extension is the missing piece that transforms a narrow kitchen.
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Sometimes combining a single-storey extension with a loft conversion makes more sense than adding a double-storey rear extension.
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Sometimes the answer is an orangery, a conservatory extension or a carefully designed garden-facing dining room rather than a large open-plan space.
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The right decision depends on the property, the household and the budget.
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APN Extensions has been created to help homeowners explore those decisions with clearer information and a realistic understanding of what is involved.
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Tell Us About Your Extension
Planning an extension or trying to understand the best way forward?
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Tell us a little about your property, the type of space you would like to create and the stage you have reached.
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Whether you are exploring your options, preparing drawings, getting ready to build or dealing with a project that is already underway, APN Extensions can help you understand the next steps and, where appropriate, connect you with suitable extension professionals.