By Huw Morris

Getting to grips with permitted development

Looking to add more space to your home? You may be able to do so under permitted development rights.

So you want more space at home. Maybe an elderly relative is moving in or there’s a new addition to the family. Maybe you need office space to work from home, or an extra room for dining, a kitchen or even utilities. Or you simply want to add value to your property.

Before calling the builder, it’s worth researching your options. Permitted development, which is laid down by parliament rather than local authorities, allows homeowners to make changes to their property without the need for planning permission. The most common forms of permitted developments are loft conversions, single-story rear extensions and side extensions.

However, balconies, verandas and raised platforms above 30mm do not fall under permitted development. It is also restricted in ‘designated areas’, such as conservation areas, world heritage sites, areas of outstanding natural beauty, as well as the Norfolk or Suffolk Broads. There are tougher requirements when permitted development is applied to listed buildings.

The following rules apply in England but are similar in Wales, Scotland and Northern Ireland – check with your local planning department if you are unsure.

What are your permitted development rights?

Firstly, they only apply to houses and outhouses; never flats or maisonettes. Some – but not all – of the criteria are:

For loft conversions

  • development adds less than 40 cubic metres to a terraced house, or 50 cubic metres to a detached or semi-detached house
  • uses similar building materials to the house
  • sits lower or equal to the highest part of the roof
  • a dormer wall that is set back at least 20cm from the existing wall face
  • has windows that are non-opening if less than 1.7m from the floor level
  • has side windows that are obscured or frosted

For extensions

  • must be on the side – as long as it does not face a highway – or at the rear of the property
  • must not extend beyond the rear wall of the house by 3 metres if an attached house, or 4 metres if detached
  • uses similar building materials to the house
  • takes up less than 50% of the size of the land around the original house (as it was first built or as it stood on 1 July 1948 if built before that date)
  • if a side extension, is less than 50% of the width of the original house
  • is below 4m in height or below 3m if within 2m of a property boundary
  • has eaves and a ridge that are no taller than the existing house

What are the dos and don’ts?

Nick Stockley has 18 years’ experience in permitted development rights and is head of design and planning at Resi Design, a leading architect that handles between 80 and 90 permitted development applications a month.


“If homeowners want to work with a good builder, they should be expecting to wait at least four months and as a general rule, the larger the project, the longer the wait”

Brian Berry, chief executive, Federation of Master Builders


“It’s a very slick, clean exercise, it’s not overcomplicated, and not overly expensive. You are spending money at the front end but it saves tens of thousands at the backend,” he says.

Stockley has the following advice for homeowners looking to carry out a project under permitted development:

Employ an architect

Speak to a qualified architect with experience of designing lofts and extensions in your local area – most have free consultation services to explore your options. They will draw up plans that comply with permitted development and building regulations.

“A good architect with experience in the residential sector specialising in small-scale development will be able to take you on that journey,” Stockley says.

Apply to your council for a lawful development certificate

A Lawful Development Certificate ensures that any past, present or future building is compliant and protects homeowners when they sell their property. It requires evidence verifying your application, particularly your architect’s plans and drawings, a site location plan and a fee [currently 50% of the cost of the corresponding planning application – a planning application of this type in England, for example, would typically cost £206].

Tell your neighbours

“If you start building and haven’t served notice on the neighbours under the Party Wall Act, their lawyers could get on to you and that could mean serious delays,” Stockley warns.

Get a builder

“A competent architect will know plenty of reputable builders that they have worked with in the past and can recommend a third party who will not expose their work and brand to risk,” says Stockley. “The builder will need to have the right insurance in place and will ideally have done work locally that the homeowner can look at.”

Seek guidance

The Planning Portal is a free online resource that explains the terminology and offers information on what to consider. Browsing home design magazines (such as Homebuilding & Renovating or Grand Designs) and speaking to architects can give you a good idea of what other homeowners have done, and what might be achievable for your own home.

Homeowners must follow the rules

“Permitted development rights only apply to a handful of developments and they are subject to a number of exceptions, limitations and conditions,” says David Bird, a partner at law firm VWV. “It is important to be sure that permitted development rights do actually apply to the development.

“Relying on permitted development rights can be risky without appropriate advice. The potential consequences of getting it wrong are the local planning authority requiring a full planning application submission or, potentially, an injunction to stop works and return the development to its original state.”

Every week Stockley sees homeowners who have not followed the rules. “If you don’t appoint an architect and go straight to a builder, they can construct something that is not in accordance with permitted development. This could result in a complaint to the council and if it doesn’t conform, you can get an enforcement letter that will either say you have to remove the structure or apply for retrospective permission, for which there is no guarantee.

“If it doesn’t get approved you will have to take it down.” In the very worst-case scenario, this could mean a hefty fine.

Remember to plan ahead

Federation of Master Builders chief executive Brian Berry says homeowners must plan up to seven months ahead if they want a successful home improvement project.

“When looking to appoint a builder, alarm bells should ring if they say they can start next week,” he says. “Experienced and professional building firms are booked up far in advance and it’s always worth waiting for these firms if you want a stress-free experience and a quality finish.”

Homeowners should expect to wait at least four months for a quality builder to be available. When this is combined with the time various home improvement projects take to complete, they are likely to have to wait a total of:

  • seven months for an extension
  • six and a half months for a loft conversion
  • just under five months to remove an internal wall to create an open-plan kitchen or diner

“Not only do homeowners need to consider how long a project takes to complete, they also need to remember how long they should expect to wait for a quality builder to be available to get going on their project,” Berry says. “If homeowners want to work with a good builder, they should be expecting to wait at least four months and as a general rule, the larger the project, the longer the wait.”