Design Guidance for House Extensions - SPG1 - Design Guidance for House Extensions Introduction

Oct 28, 2026

Design Guidance for House Extensions (SPG1) explains how to extend a dwelling while preserving local character and avoiding adverse effects on neighbouring properties and the wider area. It outlines when planning permission is required under the Town and Country Planning framework and defines what counts as an extension. The guidance emphasizes good design, respecting the appearance of the original house, using appropriate traditional styles for older properties, and avoiding extensions that dominate in scale, materials, or location.

LanguageEnglish

CategoryLifestyle

FormatPDF

Pages8

Reading Time12 min

AccessFree to download

Introduction

Legislation

The Importance of Good Design

Design Principles General

Roofs

Previous | Next | Home Design Guidance for House Extensions SPG1 Design Guidance for House Extensions Introduction 1.1 Extending a house provides a cost-effective option for increasing living space and improving the appearance of a house. However, if everyone extended their properties as they wished problems could becaused to neighbouring properties and others living in the vicinity. Similarly, the whole appearance of an area might be spoiled. 1.2 One aim of this guidance is to ensure that new housing extensions respect the local character. This does not infer that all new extensions should copy the designs of the past, but rather an appreciation of traditional local architecture combined with thoughtful application of modern building techniques and suitable materials should influence basic design principles. Legislation 1.3 The Government has established the legal framework concerning the types of work that require planning permission. The Town and Country Planning (General Permitted Development) Order 1995 sets out the types of development which can take place without the need to apply for planning permission, and hence planning permission is not always required in order to erect an extension. Table 1 at the back of this document offers assistance in deciding whether a proposal is exempt from the need for planning permission. GREATER DETAIL AND/OR CONFIRMATION AS TO WHETHER OR NOT PLANNING PERMISSION IS REQUIRED CAN BE OBTAINED FROM THE COUNCIL’S DEVELOPMENT CONTROL SECTION. 1.4 The definition of an extension covers all external additions to a dwelling and can include conservatories, garages and dormer roof extensions. Any other building, including sheds, greenhouses and aviaries erected within 5 metres of the dwelling and of a volume greater than 10 cubic metres, is also classed as an extension. 1.5 The following need planning permission without exception: l all extensions to flats (including garages, garden sheds and similar structures); and l all material alterations (whether internal or external) to Listed Buildings (buildings of architectural and historic importance); and l all sub-division of dwellings to create another separate dwelling, for example “Granny Flats”; and l any structure intended for non-domestic use (i.e. related to a business or commercial activity being undertaken in addition to the main domestic use of the property) . 1.6 Applicants for planning permission and persons carrying out works permitted under the circumstances outlined in paragraph 1.3 above should also check with the Council as to whether an application for approval is required under the Building Regulations which are the national regulations that control the minimum standards of construction for most types of building. SPG1-4 North Lincolnshire Local Plan-Adopted Plan May 2003 1 Previous | Next | Home Design Guidance for House Extensions The Importance of Good Design 1.7 It is always worth making the effort to work out a good design which will fit in with the appearance of the original house. It is beneficial to seek professional advice on the layout and design of extensions, because, whilst this may result in a greater initial expense, in the longer term there maybe benefits from reduced maintenance costs and increased property values. There may be more than one way of providing additional household space, and rough sketch plans can be helpful in comparing different schemes. Informal advice on design matters can be offered by the Council’s Development Control Section at this stage, and may save unnecessary expenditure on preparing detailed plans which would not meet Council policies. 1.8 One of the basic facts that must be recognised is that every property, by its nature, has limits for extension. It is worth bearing in mind that some houses were never designed to be extended at all, or have already been extended to their limit. For example, a loft conversion with dormers cannot be fitt

FAQs

What is the main purpose of the house extension guidance?

To ensure new housing extensions respect the local character while applying thoughtful modern building techniques and suitable materials.

When is planning permission required for extensions?

Planning permission is required without exception for extensions to flats, material alterations to Listed Buildings, sub-division of dwellings (e.g., “Granny Flats”), and any structure intended for non-domestic use.

What design principles are recommended to avoid harming the original property’s appearance?

Extensions should fit the original house so they do not look like an afterthought, should not dominate the original building in scale, materials, or situation, and traditional local styles should be used for older properties.

Oct 28, 2026

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