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Self build exemption - residential extension

There are three types of self build exemption:

  • self build exemption - for a whole house
  • self build exemption - for a residential annexe
  • self build exemption - for a residential extension

The exemptions apply to anybody who is building, or commissioning, their own home, residential extension or residential annex. Individuals claiming the exemption must own the property and intend to live in it as owner-occupier for a minimum of 3 years following completion.  

Residential extension

If the new build floorspace of your residential extension is 100sqm or more, then you will be liable for CIL. Residential extensions below 100sqm are already exempt from the levy under the minor development exemption.

You can apply for exemption from CIL if you are building a residential extension. You must have a material interest in the main dwelling (own or have a leasehold of seven or more years). Any extensions must be an enlargement to the main dwelling.

Claims for a self-build exemption for a residential extension should be submitted on Form 9: Self Build Residential Extension Exemption Claim Form. This form is available using the link below. The form specifies what additional information should accompany the claim.

You must submit an assumption of liability notice and a commencement notice before starting any work, otherwise the full amount of CIL will be payable.

Important note

It is important that you don't begin work until you submit your application for exemption and you receive notice from us with a decision. If you start any work, including digging foundations, your application for exemption will be refused.

If you fail to submit a commencement notice before starting any work, then we will charge the full amount for CIL.

We can also impose surcharges, in addition to the full CIL charge.

State aid

Self build exemptions cannot be granted if they would constitute a notifiable state aid.


Level 3 Privacy Notice: How we handle your data

We will use the information you provide to us to administrate the CIL liability relating to your development. As CIL has been adopted by the Council, this information is required by law.

For further information as to how we handle your data, please see the Level 2 CIL Privacy Notice. Hard copies are available on request. If you would like to discuss this notice, or how we will use your personal data, you can contact the CIL Officer via CIL@westlancs.gov.uk or on 01695 585171.