Building regulation drawings for extensions: what is needed?

You need to provide building regulation drawings if wish to extend your home. Let’s look at what may be required…

Do extensions have to comply with building regulations?

In a word: yes. Whilst you may not be required to submit a planning application (permitted development might be enough), you are still legally obliged to ensure that your home extension complies with UK building regulations.

Failure to comply with building regulations can result in legal penalties, fines, or even imprisonment, and can also result in problems with insurance, mortgages, and property values.

Submitting building regulation drawings to building control

To avoid any costly mistakes, you may need to make an application to building control.

In this application you will specify how each part of your building project complies with building regulations. It usually comprises of a set of building regulation drawings and a structural design.

Building regulation drawings & structural design: what’s covered

The technical drawings and construction details will cover every aspect of the project. Generally, your extension will need to comply with building regulations in the following areas:


This is the most frequently inspected stage of the build, so it is important that the drawings consider both structural stability and site preparation.

Factors to consider include:

  • The load-bearing capacity of the ground being built on
  • The presence of nearby trees
  • Any adjacent buildings or drainage systems in close proximity
Ground floors:

There are three main areas of compliance when it comes to ground floors, namely:

  • Structural stability
  • Resistance to damp
  • Prevention of heat loss

Structural stability:

Your building control application will indicate how floors will be constructed, usually as a solid concrete slab, traditional suspended timber joists or a series of suspended concrete beams infilled with blocks.

Beam/joist sizes and span calculations must be calculated by a structural engineer. These calculations must be included on your building regulation drawings.

Resistance to damp:

Your building regulation drawings must include ventilation and damp proof membranes.

What’s more, if any areas are at risk from radon, the plans must demonstrate how these areas will be ventilated.

Prevention of heat loss:

Insulation must comply with the required levels and all relevant calculations provided within the application.

Main walls

To comply with building regulations, your drawings must demonstrate the building’s:

  • Structural stability
  • Durability to the elements
  • Thermal efficiency

Structural stability:

This includes:

Cavity walls:

Cavity walls require wall ties that hold the two eaves together; building regulation drawings will indicate where the wall ties will be inserted and spaced.

Roof and floor loadings:

Building regulation drawings will consider how walls provide support for the roof and floors. Designs for window and door openings will be included, together with lintels.

What’s more, if any openings are located near corners of walls then alternative support will be provided.

Durability to the elements:

Your building plans will demonstrate that the building is protected from the weather:  below ground-level, for example, materials that are resistant to sulphate and frost could be used.

Thermal efficiency:

Building regulation drawings will indicate how your building will be thermally efficient, such as using cavity insulation and the prevention of thermal bridging.

Structural openings

Your extension may involve opening up existing walls or creating open plan spaces.

Therefore, your building regulation drawings will need to demonstrate how these loadings will be supported. For example, steel beams are often specified, based on the structural engineer’s calculations.

Upper floors

Upper floors provide lateral restraint and rigidity to the main walls, in addition to supporting internal walls, furniture and occupants.   

To ensure compliance, building regulation drawings and structural designs will specify:

  • Type of floor and ceiling joists
  • Correct spans and spacings
  • Fixings, such as joist hangers, straps, struts and noggins
  • Fire resistance and soundproofing

A structural engineer will specify various structural considerations to ensure compliance, including:

  • Type and quality of timber used for rafters
  • Steel beams used in roof structure
  • Type of roof coverings, such as tiles, slates, flat roof membranes
  • Levels of ventilation and insulation
Other considerations for building regulation drawings

The above is by no means an exhaustive list and your building control application may also require drawings and calculations for: 

  • Chimney flues and stacks
  • Windows and doors
  • Internal walls
  • Internal joinery

Building regulation drawings from CR Designs

Our team of skilled architects and structural engineers can prepare the drawings and technical specifications of your project for a building control application.

Using planning drawings prepared by either ourselves or by third party architects, the design team will have your building control package ready in 2-3 weeks and will submit it on your behalf, acting as your agent with the council for the duration of the process.

Find out more about our building regulation drawings and construction specification packages.

Make your home extension dreams a reality

Our comprehensive and affordable design packages are suitable for all types of house extension, renovation and self-build projects.

To find out more, get in touch today.

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