Buying a home with an extension?  What you need to check

Buying an extended or modified property is potentially risky. there are a number of critical things to check before making an offer.

Rear extension

Enforcement notices

Local authorities can serve enforcement notices against any property owner for breaches of the law if a property has been extended without the necessary planning consents or building regulations. This might require the extension to be modified or demolished, or you being fined or even imprisoned if you fail to address the breaches – even if you were not the property owner at the time the work was carried out.

What should I check?

Some extensions may fall within the limits allowed by Permitted Development (PD) - others may have been built with full planning permission. Apart from porches and conservatories, extensions also need to conform to Building Regulations, even where they are permitted developments.


Buying a property? Read our guide on how to compare conveyancing quotes and avoid the pitfalls.

What is Permitted Development?

Permitted development is a term given to works which may technically require planning permission but for which permission is deemed to be granted under a general permitted development order.

Generally, this means a property may be extended to the rear or side without planning permission providing it meets certain criteria on its overall size (less than 15% of the original volume – or 10% if the house is part of a terrace), doesn't extend too far from the original property and doesn't take up more than 50% of the garden area.

The exact legislation is detailed in the Town and Country Planning (General Permitted Development) Order 1995 as amended by the Town and Country Planning (General Permitted Development) (Amendment) (No. 2) (England) Order 2008.

Planning permission is required when:

The proposed extension is:

  • Greater in volume than 115 cubic metres
  • Higher than the original roof height
  • Extends beyond the dimensions allowed for permitted development – for example 3m from the original property for a 2 storey extension
  • If a property has already been extended and a new extension exceeds the 15% (or 10% for a terrace) limit.
  • The property is a listed building or in a conservation area

Building Regulations

Ensuring that building work complies with building regulations is usually the responsibility of the builder employed to complete the project, although the property owner is ultimately the person who may be served with an enforcement notice where the work does not meet the right standards.

A certificate of compliance with the building regulations should be issued to the property owner and the local authority should be notified that the work has been carried out in accordance with the regulations.

How might a property owner have breached planning regulations?

Sometimes a home-owner may unwittingly overstep the mark and build something outside the rules of permitted development, without obtaining planning permission.

For example; where a property owner believed he didn't need planning permission for a conservatory but did not consider its overall dimensions or did not take account of the property's previous extension he may find himself in breach of the planning regulations. In another situation he might also convert a loft into an extra bedroom without any building regulations checks.

Sometimes these issues are only revealed at the time the property owner decides to sell his home.

What should a prospective buyer consider?

Firstly, has the house been extended at all? This may not be obvious – some houses are built with conservatories and with attic bedrooms. If there has been an extension is it within the permitted development rules?

  • Does it appear over large or take up a large proportion of the garden?
  • Does it encroach on the neighbouring boundary?
  • Do the dormer windows seem higher or wider than the existing roof line?

Ask the owner if there is any evidence to support the work that has been done. This could be details of approved planning permission, or even a Lawful Development Certificate, which can be provided by the local authority on request to prove the extension meets planning control requirements as a permitted development. If the owner is unable to produce any documentation, ask when the work was completed.

If it was more than 4 years ago and the local authority has not taken any action for breach of planning regulations, it will not now be able to do so.

Peace of mind with indemnity insurance

Where the extension was added in the last 4 years the property owner may risk being served with an enforcement notice.

Ask if there has been any discussion with the local authority with regard to the work. If there has been no discussion for at least the previous 3 months it may be possible for the home-owner to pay for a legal indemnity insurance policy to provide cover against the risk of legal action being taken for a breach of planning regulations.

The owner will need to confirm that the house has been used for residential purposes for at least the last 12 months and that the work was completed more than 12 months ago. If there are no certificates of completion to show the work met Building Regulations a further indemnity insurance can be bought to cover this.

Legal indemnity insurance provides cover for the life of the property and is automatically transferred to each new owner of that property. However it is invalidated if the home-owner contacts the local authority about the property.

How can Quittance help?

If you are buying, selling, remortgaging or transferring equity in a home, our conveyancing solicitors can help.

Our conveyancing service aims to deliver a stress-free moving experience. In particular we focus on proactive communication as this can help drive a purchase or sale forwards to speedy completion.

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Gaynor Haliday, Legal researcher

About the author

Gaynor Haliday is an experienced legal researcher and published author. She has had numerous articles published in the press and is a legal industry commentator.

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