A guide to extending under permitted development

Add extra space to your home without the need for planning permission and you can save time and money.  Here’s what you need to know.

Speedier improvement

An extension under PD transformed the awkward ground-floor layout of the house Louise and Dave Brown share with their two boys.

‘Our house had a weird L-shaped half open plan design,’ says Louise. ‘You’d come in the front door and there was only one way to access the rest of the ground floor through the living and dining rooms.  It was like a corridor.  The house had a conservatory at the back – a lean-to design that was about 40 years old.  In summer it was way too hot and in the winter it was freezing.  ‘Once we’d made the decision to improve we wanted to do the work as quickly as possible, which permitted development allowed.  I think we did the right thing.  My neighbours had done a massive extension and it look about nine months alone to get planning permission for the project.

‘Using permitted development didn’t constrain us.  We’d already decided we were happy with the square footage of the house – it was just that the space wasn’t used effectively.  When the boys were growing up, we were always in one small area of the living room, so we wanted a family room.

‘The conservatory had to go because it was practically falling down, and we extended onto the footprint.  We put a wall half way through the open-plan area and created two rooms.

From the hall there’s now the choice to go into the front room or the new family room.  The front room has an open fireplace, so we were keen to keep it and now its a real retreat.

‘I particularly like the layout of the back room.  I’m really proud of the seating area with the built-in units and desk space.  It’s cosy and works brilliantly; we all tend to watch TV there.  It’s a social room with plenty of places to sit with the bar stools, dining chairs and L-shaped sofa to lounge on.  The front room’s used at Christmas and when we want to sit by the fire’.


If you want to build a single-storey extension under PD in England, the addition, together with any previously build (even if not by you), can’t exceed 50 per cent of the area of land around the original house.  This is what was there on 1 July 1948 if it was built before then, or as it was first built if it was constructed later than that.  Sheds and outbuildings count in the 50 per cent limit.  The same rules around area apply for two-storey extensions, too.


A single storey extension under PD can be at the side of your house providing you don’t live in a designated area, or at the rear.  Extensions forward of the principal elevation or side elevation of a house and fronting a highway are not PD.  You can’t go up by two storey’s at the side either.


A side extension can’t be wider than half the width of the original house.  The maximum height is four metres.  Rear extension have the same maximum height and can’t go more than three metres beyond the rear of the original house if it’s attached, or four metres for a detached.  However, until 30 May 2019 (and outside designated land and Sites of Special Scientific Interest), these limits are six metres (attached) and eight metres (detached), subject to the neighbour consultation scheme.  Find house more on realhomes.com/planning permission.


You can go up two storey’s at the rear of the house under PD provided you don’t live on designed land.  Two-storey extensions can’t have an eaves and ridge height higher than the existing house, or over three metres if the addition is within two metres of the boundary.  They can’t go more than three metres beyond the wall of the original house or be within seven metres of any boundary opposite its rear wall.  Read more on planningportal.co.uk


Using permitted development doesn’t mean you can avoid other requirements when you’re building.  Your work will need to abide by building regulations and you’ll have to consider the requirements of party wall legislation when notifying neighbours.  Get details about both on the Government’s planning site, planningportal.co.uk.


Project cost ?49,070
Design and build Plus Rooms 0800 917 7127 plusrooms.co.uk