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What are permitted development volume limits?

To qualify as permitted development some household building work projects – notably extending a house – must not exceed limits to the volume being added.  

In England, the volume allowance mostly applies to loft conversions. You can read more on the Planning Portal. 

Use the volume calculator to find out the volume of several loft conversion and extension types.

Common Questions

What are the rules for installing a septic tank in the garden?

Installing a new septic tank in your garden will often require both planning permission, building regulations approval and a septic tank permit.

The planning permission will ensure that the tank is installed in an appropriate location with information being provided to understand any potential implications for the surrounding environment and water.

Building regulations is required for the installation of a septic tank to ensure it meets the drainage and waste disposal standards set out in Approved Document H.

Where possible it is recommended that you connect to an existing public sewer instead of installing a septic tank, this reduces waste entering the waterways.

For more information visit our drains common project or contact your local planning authority.

What do I need to know about new foundations for an extension?

Foundations are required to carry and distribute the load of the building safely. Therefore, all buildings should have adequate foundations. The factors that need to be considered when designing a foundation are:

  • Type of soil
  • Adjacent structures
  • Trees
  • Drains and sewers
  • Size and construction of the new building
  • Ground condition
  • Landfill sites

It is advisable to contact a structural engineer or speak to a building control body about plans for new foundations. 

Read more about foundations for extensions.

What do I need to know if I want to add an internal wall to make another room in my house?

Adding an internal wall will not require planning permission or building control approval in most cases. If the building is listed, then you may require listed building consent to make a major alteration to the house.

Any work completed should adhere to building regulations, ensuring fire routes, electrics and ventilation are considered.

Do I need planning permission to demolish a building?

Demolishing a building may require planning permission or prior approval, depending on factors such as the building’s type, size, and location.

Before starting any demolition work, it’s important to consult your local planning authority to confirm what permissions are needed. This helps avoid the risk of enforcement action or legal consequences.

You will also need to ensure you conform to the building regulations around the demolishing of a building.

Read more about demolition.

Can I convert a detached garage into a self-contained living space?

Yes, but you will need to obtain planning permission. Converting a detached garage into a self-contained living space, such as annexe, studio flat, or retail unit, represents a material change of use, particularly if it will function independently from the main house. This is because the garage would no longer be used in connection with the main dwelling and would effectively become a separate residential unit.

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