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Home & garden.

Updated: 29 Jun 2021

Building regulations and planning permission

Getting to grips with the different terms, from building regulations to permitted development, will put you in good stead when it comes to planning your brand new space.
Rachel Christie
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Planning an extension can be a headache, especially when there are so many different rules and regulations to get through first. This guide will simply explain the four main extension buzzwords everyone should know before they embark on their extension journey.

Find out more about extension planning and planning costs on our dedicated pages.

The more you know in advance, hopefully less surprises and hiccups should happen down the line. Here's a quick sentence to explain each area, but jump down to find more in-depth information and advice.

Building regulations

Any renovation project must comply with building regulations, regardless of planning permission. Building regulations are the minimum standard for design, construction and alterations to every building. 

You can apply to any local building control department or approved inspector for building regulations approval.

Anything that falls under building work needs to be covered by building regulations, including:

  • The erection or extension of a building
  • An alteration project
  • The insertion of insulation into a cavity wall
  • The underpinning of the foundations of a building
  • Work affecting thermal elements, energy status or energy performance of a building. 

Ensure whoever carries out the work can either self-certify the work they do (for example, FENSA accredited window fitters, Gas Safe registered gas engineers and NICEIC registered electricians, and so on) or liaise with the local Building Control Officers at your council to have their work certified. 

The responsibility is usually down to the builder, but always confirm this at the very beginning and bear in mind that if you are the owner of the building; it'll be you who is served with an enforcement notice if the work does not comply.

If the requirements aren’t met, you could be served with a notice to take the extension down and will have trouble when it comes to selling your home without the relevant building regulations certificates.

Permitted Development

Permitted development rights are a more relaxed version of planning permission. It's not granted by the local authority but by parliament. 

Permitted development allows homeowners to make alterations to their properties quickly without having to go through planning. This can include extensions, loft conversions, roof lights, solar panels and windows. This is because the effect on neighbours or the surrounding environment is likely to be small.

Certain projects won’t need planning permission and instead fall under permitted development rights. As of May 2019, under the recently extended permitted development rights, a rear wall of a detached home can be extended by 8m to the rear if it’s a single story property, 3m if it’s double storey and 6m in a semi or terraced house, without the need for planning permission. These rules were put into place temporarily five years ago, but have now been made permanent.

There are also height restrictions; a single story extension should not be higher than 4m in height to the ridge and the eaves, and ridge heights of any extension should not be higher than the existing property. If the extension is more than half the area of land around the original house, you will need planning permission.  

If you go for building regulations approval, it is advised to notify your local authority and apply for a Certificate of Lawful Development to ensure you have the proof that development fell within these rights. These applications tend to take about 10 weeks. 

Some people who initially try for planning permission abandon their planning application and revise their plans so that the work will fall within permitted development rights, instead of the more expensive and lenghty planning permission process. 

Permitted development rights are different for buildings such as flats, maisonettes and commercial property, so check the rules for the type of property you own. Also find out whether the building is in an area where rights are more restricted and different rules apply, such as a conservation area or national park. Plus, any renovations to a listed property will need listed building consent.

Planning Permission

Planning permission or planning consent is permission required in the UK granted by the local authority to build something new on land, make an alteration to a property or to change the use of a property.

The local planing authority decides whether a development should go ahead. This ensures people don't just build structures wherever they want or use land in any way they wanted. 

Navigating planning permission can be confusing. Most new buildings and major alterations to existing buildings need permission, though as discussed above, some minor building works, known as permitted development, don't need planning permission. 

The cost of planning permission varies depending on the scale of your project. Calculate a figure for a worst case scenario, including possible extras such as bat surveys, and allow some contingency in your budget. Get help working out the fee from online tools such as the Planning Portal's fee calculator or from your local authority.

How long does UK planning permission take? 

UK planning authorities have statutory time limits to deal with planning applications, which vary depending on where you live. 

  1. You'll be required to submit an application, which takes a maximum of 10 weeks to be decided, including a two-week validation period and an eight-week decision period.
  2. Allow plenty of time for planning permission approval. The more complex your plans, the more likely it is that the deadline will be extended or missed, so try and get your application right before submitting - you can consult your local planning department for help. Basic advice is usually free or you can get more formal ‘pre-application advice’ for a fee. Architects can also help with this phase of the process.
  3. Monitor the progress of your application so that you don’t miss any actions that you need to take, and respond quickly to any requests from the planning authority. 
  4. Make sure you’re prepared for delays and have a plan for what to do if you can’t start work as scheduled. If a delay leads to you losing the contractors you’d hired, you can use Which? Trusted Traders to search for builders in your area to help you get your project back on track. All endorsed traders have been through our rigorous assessment process and have signed up to our Code of Conduct.

Party wall agreements

A party wall is a shared wall, usually between a terrace or semi-detached house, and divides the homes of two separate owners. Party wall agreements are something you need to know about it you’re planning an extension or renovation next to an adjoining property in England or Wales. 

The Party Wall Act 1996 is designed to help you undertake work, while protecting the interests of your neighbours.

Party wall agreements are most commonly needed for loft conversions and extensions which require the insertion of steel supports, a damp proof course or new foundations.

If building work affects a party structure, you must serve notice at least two months before work begins. In the case of excavations, you must give at least one month’s notice. Work can begin once an agreement has been entered into.

You need to write to all adjoining homeowners, stating your name and address, a full description of the work, including the property address and start date, plus a statement that it is a party wall notice under the provisions of the Act. Before serving notice, chat to your neighbours about your plans and make sure they understand what it is you are planning to do.

You serve notice on your neighbour by writing to them and including your contact details and full details of the works to be carried out, access requirements and the proposed date of commencement. In an urban environment, your project might affect several adjoining neighbours, and you will have to serve notice on each of them. If a property is leasehold you will need to serve notice on both the tenant and the building’s owner.

Provide your neighbour with details of the Party Wall Act so that they know what they are agreeing to – you can download the Planning Portal's explanation of the Party Wall Act.

Your neighbour has 14 days to respond and give their consent, or request a party wall settlement. If they agree to the works in writing, you will not require a party wall agreement and this can save on the fees.

Find a party wall surveyor at The Royal Institution of Chartered Surveyors

Click through to our extensions costs page to find out the average cost for a single and double storey extension.