What are the laws pertaining to garden buildings and planning permission?

Permitted development (i.e. not requiring a planning application) =

E. The provision within the curtilage of the dwellinghouse of-

(a) any building or enclosure, swimming or other pool required for a purpose

incidental to the enjoyment of the dwellinghouse as such, or the maintenance,

improvement or other alteration of such a building or enclosure; or

(b) a container used for domestic heating purposes for the storage of oil or liquid

petroleum gas.

Development not permitted (i.e. if any of the following apply, you will need planning permission) =

E.1 Development is not permitted by Class E if-

(a) the total area of ground covered by buildings, enclosures and containers within the curtilage (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);

(b) any part of the building, enclosure, pool or container would be situated on land forward of a wall forming the principal elevation of the original dwellinghouse;

(c) the building would have more than one storey;

(d) the height of the building, enclosure or container would exceed-

(i) 4 metres in the case of a building with a dual-pitched roof,

(ii) 2.5 metres in the case of a building, enclosure or container within 2 metres of

the boundary of the curtilage of the dwellinghouse, or

(iii) 3 metres in any other case;

(e) the height of the eaves of the building would exceed 2.5 metres;

(f) the building, enclosure, pool or container would be situated within the curtilage of a listed building;

(g) it would include the construction or provision of a veranda, balcony or raised platform;

(h) it relates to a dwelling or a microwave antenna; or

(i) the capacity of the container would exceed 3,500 litres.

E.2 In the case of any land within the curtilage of the dwellinghouse which is within-

(a) a World Heritage Site,

(b) a National Park,

(c) an area of outstanding natural beauty, or

(d) the Broads, development is not permitted by Class E if the total area of ground covered by buildings, enclosures, pools and containers situated more than 20 metres from any wall of the dwellinghouse would exceed 10 square metres.

E.3 In the case of any land within the curtilage of the dwellinghouse which is article 1(5)

land (that means National Park, AONB, conservation area), development is not permitted by Class E if any part of the building, enclosure, pool or container would be situated on land between a wall forming a side elevation of the dwellinghouse and the boundary of the curtilage of the dwellinghouse.