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Practical advice for planning a residential extension

Request Professional Support

Every extension project is different. Tell us about your property, your plans and the stage you have reached, and we can help connect you with suitable professionals for the next steps.

Planning a house extension can feel complicated.

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You may have a clear idea of the space you want to create but be unsure which professionals you need, what should happen first or how the different stages fit together.

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You may already have planning drawings and need Building Regulations support.

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You may have received builder quotations that are difficult to compare.

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You may be preparing to start work and need structural calculations, Party Wall advice or specialist suppliers.

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Or you may simply be at the beginning and want to understand your options.

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Tell us a little about your project and the stage you have reached. We can help connect you with suitable extension professionals.

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What Support Do You Need?

 

Depending on your project, you may need help with one or more of the following:

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  • Architectural design and planning

  • Planning applications

  • Permitted-development advice

  • Lawful Development Certificates

  • Building Regulations drawings

  • Structural calculations

  • Structural engineers

  • Building Control and registered building control approvers

  • Party Wall advice

  • Party Wall notices and Awards

  • Extension builders

  • Project management

  • Glazing, rooflights and doors

  • Kitchen and bathroom specialists

  • Drainage investigations

  • Specialist surveys

  • Other trades and services

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You do not need to know every answer before contacting us.

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A brief description of your plans is often enough to identify the most appropriate next step.

Exploring Your Options

 

You may be at the early stage of deciding whether an extension is right for your home.

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Perhaps you are considering:

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  • A rear extension

  • A side-return extension

  • A wraparound extension

  • A full-width extension

  • A double-storey extension

  • A bungalow extension

  • A kitchen and dining-room extension

  • A conservatory or orangery-style extension

  • An extension combined with a loft conversion

  • Internal remodelling alongside an extension

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At this stage, the priority is to understand what may be possible, what approvals may be required and whether the likely budget is realistic.

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A smaller, carefully designed extension may sometimes transform a property more effectively than the largest possible addition.

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The right solution depends on the home, the available space and the way you want to use it.

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Design and Planning Support

 

A well-designed extension begins with a clear brief and suitable drawings.

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Depending on the project, design and planning support may include:

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  • Reviewing the existing property

  • Discussing your priorities

  • Exploring layout options

  • Preparing measured drawings

  • Developing the proposed design

  • Checking the likely planning route

  • Preparing planning drawings

  • Submitting a planning application

  • Advising on permitted development

  • Preparing a Lawful Development Certificate application

  • Responding to planning queries

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Some extensions can be built under permitted development rights.

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Others require a formal planning application.

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The correct route depends on the type of property, the size and position of the proposed work and any restrictions affecting the home.

Building Regulations Drawings

 

Planning drawings are not normally enough for construction.

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Once the design has been agreed, a more detailed technical package may be required.

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Building Regulations drawings may address:

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  • Foundations

  • External walls

  • Floors

  • Roof construction

  • Insulation

  • Ventilation

  • Drainage

  • Fire safety

  • Windows and doors

  • Rooflights and roof lanterns

  • Structural references

  • Materials

  • Construction notes

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Most house extensions need Building Regulations approval even where planning permission is not required.

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A proper technical package can help builders quote more accurately and reduce avoidable uncertainty during construction.​​

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Structural Design

 

Many extension projects require a structural engineer.

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This is particularly common where the homeowner wants to remove the original rear wall and create a large open-plan kitchen, dining and family area.

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Structural design may be needed for:

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  • Steel beams

  • Columns

  • Padstones

  • Large structural openings

  • Removing load-bearing walls

  • Roof alterations

  • Chimney-breast removal

  • Double-storey extensions

  • Foundation design

  • Temporary supports

  • Complex glazing arrangements

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Structural calculations should be coordinated with the Building Regulations drawings so that the builder receives a clear and consistent package.

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Party Wall Advice

 

Some extensions may require notices under the Party Wall etc. Act 1996.

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This may be relevant where the work includes:

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  • Excavating close to a neighbouring building

  • Building on or close to a boundary

  • New foundations below the level of neighbouring foundations

  • Cutting into a shared wall

  • Inserting steel beams into a party wall

  • Raising or altering a shared wall

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Not every extension requires a Party Wall Award.

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However, the issue should be checked before building work begins.

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Leaving Party Wall matters until the builder is ready to start can create unnecessary delays.

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Find Extension Builders

 

Finding the right builder is one of the most important decisions in the project.

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The best choice is not automatically the builder with the lowest headline price.

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A suitable extension builder should understand the drawings, explain the quotation clearly and have relevant experience with similar work.

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Depending on the project, you may need a builder for:

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  • Rear extensions

  • Side-return extensions

  • Wraparound extensions

  • Full-width extensions

  • Double-storey extensions

  • Kitchen extensions

  • Bungalow extensions

  • Conservatories and orangeries

  • Garage conversions

  • Internal remodelling

  • Structural alterations

  • Extensions combined with loft conversions

  • Larger home-renovation projects

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The more information you can provide, the easier it is to identify suitable professionals.

Compare Builder Quotations

 

Builder quotations can vary significantly.

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A cheaper quotation may exclude structural steelwork, drainage alterations, glazing, electrical work, decoration or VAT.

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Another quotation may look more expensive because it includes a broader and more realistic scope of work.

Before appointing a builder, compare:

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  • The drawings used for pricing

  • The scope of work

  • Inclusions

  • Exclusions

  • Provisional sums

  • Foundation allowances

  • Drainage assumptions

  • Structural steelwork

  • Glazing

  • Plumbing

  • Electrical work

  • Kitchen installation

  • Finishes

  • VAT

  • Payment stages

  • The proposed programme

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A proper comparison can help reveal hidden differences and reduce the risk of expensive surprises later.

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Project Already Underway?

 

You may already have a project in progress and need help with a particular issue.

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This might include:

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  • Reviewing an existing design

  • Updating drawings

  • Preparing Building Regulations details

  • Arranging structural calculations

  • Dealing with drainage issues

  • Finding a replacement builder

  • Comparing quotations

  • Obtaining Party Wall advice

  • Sourcing glazing, rooflights or doors

  • Identifying specialist trades

  • Resolving a gap in the construction information

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The earlier the issue is identified, the easier it may be to resolve.

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Provide as much information as possible, including any existing drawings, approvals, photographs and quotations.

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What Information Should You Provide?

 

You do not need to prepare a complicated report.

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A few practical details will help.

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Tell us:

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  • The property location

  • The type of property

  • The type of extension

  • The approximate size

  • The stage you have reached

  • Whether drawings are available

  • Whether planning permission has been obtained

  • Whether Building Regulations drawings are available

  • Whether structural calculations have been prepared

  • Whether builders have already quoted

  • The type of support you need

  • Your approximate timescale

  • Your preferred contact details

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Photographs, drawings and quotations can also help provide a clearer picture.

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A Coordinated Approach

 

A successful extension usually involves more than one professional.

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The designer, structural engineer, Building Control body, Party Wall surveyor and builder may all have separate roles.

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The best results are usually achieved when the work is coordinated properly and the drawings are sufficiently developed before construction begins.

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This can help:

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  • Reduce misunderstandings

  • Improve builder quotations

  • Identify technical issues earlier

  • Avoid unnecessary delays

  • Reduce the risk of additional costs

  • Make the construction process easier to manage

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Tell Us About Your Extension

 

Whether you are exploring your options, preparing a planning application, looking for builders or trying to resolve an issue on site, tell us a little about your project.

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We can help connect you with suitable professionals for the next steps.

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