Look at the Existing House Properly

 

A good extension design should consider the whole property, not just the new structure.

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Sometimes a modest extension combined with internal alterations will create a better result than a much larger addition.

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The design stage may consider:

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• whether walls can be removed;

• whether the kitchen should move;

• whether the dining area feels disconnected;

• whether the rear reception room is underused;

• whether a utility room would improve the kitchen layout;

• where natural light is needed;

• whether storage has been planned properly;

• how the extension connects with the garden;

• whether circulation can be improved; and

• whether the existing layout still works once the extension is added.

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The aim is to make the new and existing parts of the home work together.

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Measured Survey

 

The design process usually begins with a measured survey of the existing property.

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This creates an accurate record of the parts of the home relevant to the project.

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The measured survey may include:

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• floor plans;

• external walls;

• internal walls;

• doors and windows;

• room dimensions;

• ceiling heights;

• roof forms;

• existing drainage positions where visible;

• garden levels where relevant;

• neighbouring relationships;

• and other features that may affect the design.

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Accurate information at this stage helps reduce mistakes later.

Existing Drawings

 

Once the survey has been completed, existing drawings can be prepared.

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These may include:

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• existing floor plans;

• existing elevations;

• existing roof plans;

• and site or location plans where required.

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These drawings show the current property before any alterations are made.

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They provide the starting point for the proposed design and may also be needed for a planning application.

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Proposed Design Drawings

 

The proposed drawings show how the property may look after the extension and alterations have been completed.

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Depending on the project, these may include:

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• proposed floor plans;

• proposed elevations;

• proposed roof plans;

• site plans;

• block plans;

• sections;

• layout options;

• and supporting diagrams.

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The drawings may identify:

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• the size of the extension;

• wall removals;

• new openings;

• the proposed kitchen location;

• utility rooms;

• ground-floor WCs;

• bedrooms;

• roof form;

• door and window positions;

• rooflights;

• roof lanterns;

• glazing arrangements;

• and the relationship with the garden.

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Rear Extensions

 

A rear extension can be one of the simplest ways to increase ground-floor space.

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It may help create:

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• a larger kitchen;

• a kitchen-diner;

• a family room;

• a home office;

• a utility room;

• wider garden access;

• or a brighter rear living space.

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The design should consider the extension depth, roof form, glazing, internal layout and the amount of garden retained.

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Side-Return Extensions

 

A side-return extension uses the narrow strip of land beside the rear projection of a terraced or semi-detached house.

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This can be particularly effective where the existing kitchen is narrow or disconnected from the dining area.

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A successful side-return design may include:

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• a wider kitchen;

• a dining area;

• rooflights;

• a partly glazed roof;

• a roof lantern;

• sliding doors;

• fixed glazing;

• and improved circulation.

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The design needs to consider how daylight reaches the centre of the property.

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Wraparound Extensions

 

A wraparound extension combines a rear extension and side-return extension.

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This can create a larger and more flexible ground floor.

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Depending on the property, it may allow space for:

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• a generous kitchen-diner;

• a family area;

• a utility room;

• a pantry;

• a WC;

• additional storage;

• and improved access to the garden.

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Wraparound extensions require careful design because the scale, roof arrangement and relationship with neighbouring properties can become more important.

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Double-Storey Extensions

 

A double-storey extension may provide additional space on both floors.

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This can help create:

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• a larger kitchen or living space downstairs;

• an additional bedroom upstairs;

• an en-suite bathroom;

• a better family bathroom;

• a home office;

• and improved storage.

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Two-storey additions normally require more careful planning because their visual impact and effect on neighbouring homes can be greater.

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Extensions and Loft Conversions

 

Some homeowners choose to plan an extension and loft conversion together.

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This can be sensible where the property needs both a larger ground floor and additional bedroom space.

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Thinking about the projects together can help coordinate:

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• the staircase position;

• structural alterations;

• roof design;

• internal layouts;

• drainage;

• planning applications;

• construction sequencing;

• and the overall budget.

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A joined-up design can reduce the risk of one project creating problems for the other.

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Kitchen Design Should Be Considered Early

 

Many extensions are created around the kitchen.

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The kitchen layout should not be left until the final stage.

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It can affect:

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• window positions;

• door openings;

• rooflights;

• drainage;

• plumbing;

• electrical layouts;

• lighting;

• structural columns;

• wall positions;

• and circulation space.

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A kitchen island, dining table and seating area all need enough room to work properly.

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The extension may look generous on paper, but the space still needs to function comfortably in everyday life.

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Glazing, Rooflights and Natural Light

 

Natural light is one of the most important parts of extension design.

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An extension may increase the size of the ground floor but make the centre of the original house darker if the glazing is not considered carefully.

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Options may include:

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• sliding doors;

• bifold doors;

• fixed glazed panels;

• rooflights;

• roof lanterns;

• steel-look doors;

• clerestory windows;

• internal glazed doors;

• and partly glazed roofs.

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The best solution depends on:

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• the orientation of the property;

• the type of extension;

• the room layout;

• privacy;

• the garden;

• neighbouring properties;

• and the architectural style of the home.

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A large amount of glazing is not automatically the best answer.

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The design should also consider comfort, overheating, insulation, security and how the room will be furnished.

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Planning Permission or Permitted Development?

 

Some house extensions require planning permission.

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Others may fall within permitted-development rules, subject to limits and conditions.

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The correct route will depend on the property and the proposed work.

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Important considerations may include:

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• the depth of the extension;

• the height;

• the width;

• whether it is single-storey or double-storey;

• whether it is to the rear or side;

• previous extensions;

• the type of property;

• whether the property is listed;

• whether the property is within a conservation area;

• whether additional local restrictions apply;

• and the effect on neighbouring homes.

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Do not assume that your extension will automatically be acceptable simply because another property nearby has completed similar work.

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Every property should be reviewed on its own merits.

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Lawful Development Certificates

 

Where a proposal falls within permitted-development rules, some homeowners choose to apply for a Lawful Development Certificate.

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This can provide a formal record confirming the planning status of the proposed work.

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A certificate may be useful when:

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• selling the property;

• refinancing;

• keeping the property records clear;

• providing information to a future purchaser;

• or confirming the position before construction begins.

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The appropriate route depends on the project and the property.

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Planning Applications

 

Where planning permission is required, the application will normally include drawings and supporting information.

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Depending on the project, this may include:

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• application forms;

• location plans;

• site plans;

• existing drawings;

• proposed drawings;

• elevations;

• roof plans;

• sections;

• design statements;

• heritage information;

• tree information;

• and other supporting documents where relevant.

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The application process can also involve questions or comments from the local authority.

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A well-prepared submission helps explain the design clearly.