Up, up or away? The rise of rooftop extensions

The widening of the scope of permitted development (PD) is all the rage right now, but may finally have gone too far.

The government has recently thrown open for discussion the creation of additional new homes above buildings in high streets and town centres.

What is being proposed?

The MHCLG’s wide ranging “Planning Reform: Supporting the high street and increasing the delivery of new homes” consultation paper closed on 14 January. Sections 1.13 to 1.29 propose a new PD right, subject to prior approval, to allow additional storeys of new self-contained homes, above buildings particularly those in commercial or residential use.

Prior approval would be required and would be less onerous than full planning. But it would still involve assessing the impact of the development on neighbouring properties and amenity; the character of an area; and consideration of the design.

It is proposed that the PD right would apply to existing buildings with a range of uses, but the new right would not apply inter alia to

• Listed buildings and land within their curtilage
• Sites that are or contain scheduled monuments

The consultation paper discusses options, including new PD rights to build (a) up to the height of the tallest building in a terrace; or (b) up to the prevailing roof height in the locality. The second option would of course be difficult to define and would rely on the planning authority’s discretion during the prior approval process.

What will this mean for the high street?

The impact on the appearance of the high street has been much discussed, with fears of unsightly additions to the streetscape.


A more subtle danger is the loss of ‘hierarchy’ in terraces or groups of building under both suggestions. Certain buildings are designed, along with their context, to be more prominent, and should dominate. Allowing any extension to challenge their prominence, resulting from great design or their location, poses a danger to the appearance of attractive street scenes.

Will it work?

In a similar vein, how would the rules distinguish between different typologies of buildings, which would be affected in different ways?

The idea that a set of rules might prevent bad outcomes is arguably naïve, and unlikely to suit the multiplicity of scenarios that exist in a city with a fabric as complex as London’s. It will surely be impossible to formulate rules that will avoid detrimental outcomes, whilst achieving the flexibility that make PD rights worth the candle.

The problems with PD rights for householder developments are well known. But where rooftop developments are concerned these potentially amplify and make more visible the dangers of PD, especially in prominent town centre areas which will be affected by these changes.

Imagine the worst householder extension you have seen carried out under PD rights and think of it as a large building in a prominent location. That image may be the nightmare we have to come.