20 September 2011

Outbuildings and Permitted Development Rights

Most houses in England and Wales benefit from permitted development rights that allow homes to be extended without applying for planning permission. Whilst loft conversions and conservatories are the most popular forms of extension under permitted development rights, the General Permitted Development Order 2008 or GDPO is actually most generous where outbuildings are concerned. This article looks at how to get the most out of permitted development rights for outbuildings, garden rooms, summerhouses, garden sheds and home offices.

Planning Applications and Permitted Development

Permitted development rights allow homeowners to extend houses by a certain amount without applying for planning permission. This is helpful as a typical householder planning applications will take at least 8 weeks to get approved and will often face a surprising level of opposition.

Smaller schemes, however, can be built under Class E of the General Permitted Development Order 2008 (GPDO). While there is also an approval or checking process for schemes developed under permitted development rights, this is not mandatory and is relatively simple. PD rights are available on Green Belt land but can be affected by Conservation Areas, Listed Building status and Areas of Outstanding Natural Beauty.

Size and Shape

Broadly speaking, you can generally build up to 50% of the area of the curtilage (front and rear gardens). Height will fall into one of three categories, depending on the roof type and distances to the boundary.

The measurements for eaves and total height are a little ambiguous in the GDPO. Fortunately, the key eaves figure is the lower eaves, not the upper eaves or side. It is measured from the top of the roof, at the lowest point at which it meets an outside wall. Unfortunately, eaves height is measured at the top of the roof, not the bottom.

Where sites are sloping, all height measurements are relative to the nearest adjacent ground, except for buildings within 2m of the boundary, where it is relative to the lowest adjacent ground. There is little guidance on sculpting the local ground level to increase the permitted building height but this is something you could explore.

For most sites, we suggest one of two basic building types, a flat roof scheme and a taller scheme with a dual pitch (types A and C above). The base plan, details and interior of which can be adapted to suit the site and your intended use. Simple variations could include;
Porches / roof overhangs
Sliding glass doors and windows
L-shapes, cruciforms and complex plans
Gables on long elevations
Roofs following different angles from the walls

You can find the exact wording of the GDPO 2008 here or read the slightly more accessible guide from the Department for Communities and Local Government here.


Under the permitted development rights, outbuildings can be used for any purpose 'incidental to the . . . personal enjoyment of the occupants of' the main house. This can include;

home cinemas
offices or study libraries
DIY workshops for personal use
TV and games rooms for teenagers
pottery studios or hobby spaces
snooker or billiards rooms
laundry rooms

Permitted development rights do not cover living accommodation separate from the main house or 'primary living accommodation such as a bedroom, bathroom, or kitchen'. Limited kitchen and sanitary appliances can be installed, so long as they are neither totally independent from the house, nor are they the main facilities for the house. 


Weathertightness and low maintenance will be a must for any summerhouse or outbuilding. Beyond that, you might like to consider your own outbuilding in terms of;

heating requirements
electrical and data connections
plumbing connections, sinks and toilets
thermal efficiency
airtightness and ventilation
lighting quality and control
specialist fit-out such as AV and IT or hobby related equipment
sustainable materials and responsible sourcing
positive impact on biodiversity


An ideal method of construction would;

minimise wet trades on site
use prefabrication to limit the time spent on site
provide cost security
limit the use of specialist trades
make economies of scale where possible
respond to physical site constraints
visibly demonstrate sustainable principles

Engineered timber I-sections can achieve a lot of these goals and we suggest looking into products like Jewson’s range of I-joists as a starting point.

External walls

 Timber framed walls can be easily adapted to suit a range of internal and external finishes. A range of timber cladding profiles can be sourced from local merchants such as Champion Timber.  Renders and brick slips can also be applied to timber frame. More exotic external finishes such as EPDM rubber or custom laser cut steel panels could also be used. 

External appearance of roofs

The choice of materials for roofs will be strongly influenced by the size of the building and its impact on the roof pitch. The larger the building, the lower the pitch, meaning less choice of roofing materials.

Single ply membrane can work at all pitches and can be adapted to suit a range of green roof systems. Green roofs range from simple sedum blankets offering a visual greening for little maintenance to 'extensive' systems which create habitat for wild flowers, bees and butteflies.

We suggest looking into sedum blankets over single ply membrane as a starting point for residential outbuildings

I propose we offer sedum over single ply as a starting point for all designs with an upgrade to intense habitat roofs or a saving for bare single ply.

Moving forward

If you are reading this as a homeowner or landlord and would like to know more, feel free to drop us an email at studio425@london.com and we’ll be happy to help.

Sources and original documents

Original legislation

Planning Portal Interactive House