Planning Permission

Outbuildings are generally considered to be permitted development under Class E, and do not need Planning Permission, subject to a number of limits and conditions.

The most important factors are:

1) That the building is no higher than 2.5m from the bottom of the building to the top of the roof

2) That you do not take up more than 50% of your garden area with this or any other buildings

3) It is not to be used for living or sleeping accommodation

In more detail -

DEFINITION of 'Permitted Development':

'The provision of any outbuilding within the curtilage of the dwelling for a purpose incidental to the enjoyment of the dwelling, or the maintenance, improvement or alteration of such building or enclosure'.

Essentially, this means that so long as the purpose of the development is incidental to the enjoyment of the dwelling it will be classed as Permitted Development except in the following circumstances:

You are not allowed an outbuilding which projects forward of the front elevation of the original house.

Any outbuilding must be single storey and have a maximum eaves height of no more than 2.5 metres. The maximum overall height must not be more than 4 metres if a dual pitched roof is specified, or 3 metres for any other roof (See image below)
If the outbuilding is to be positioned within 2 metres of the property boundary, no part of it shall exceed 2.5 metres in height. So below 2.5m height it can be positioned as close to the boundary as is practical. (See image below)
No balconies or verandas are allowed on an outbuilding without Planning Permission.
Decking or other raised platforms can be fitted around the outbuilding, but only up to a maximum height of 300mm.
Any outbuilding must not be used as self-contained living accommodation, and must not have a TV, or Satellite type of aerial. Planning Permission will be required in these cases.
Outbuildings and other additions must not take up more than half the area of land around the "original house". “Original house” means the house as it was first built, or as it was on 1st July 1948 (If built before that date). Extensions, timber sheds and all other outbuildings must be included when calculating this limit. Although you may not have built an extension, the previous owner could have done, and this needs to be included in calculating the overall limit.
On designated land, (areas of Outstanding Natural Beauty, National Parks, the Broads, Conservation Areas and World Heritage Sites), the maximum size of an outbuilding will be limited to 10 square metres and must be 20m from any wall of the house.
On designated land (AONB etc), outbuildings at the side of the house will require planning permission.

If the original building has Listed Status, all outbuildings will need full planning permission.

Note:

This guidance applies to planning regulations in England only. Policy for Scotland and Wales may differ slightly please check with your Local Authority.

Use the Planning Portal here for more information:

https://interactive.planningportal.co.uk/mini-guide/outbuildings/0

Building Regulations

In brief:

1) Building Regulations do not usually apply unless you want to sleep in it

2) Under 15m2 internal floor area can be installed close to any rear boundary

3) Over 15m2 and up to 30m2 needs to be a minimum 1m from any boundary

If you want to put up small detached buildings such as a garden shed, garden room or summerhouse in your garden, Building Regulations (except Part P for Electrical works) will not normally apply if the floor area of the building is less than 15 square metres INTERNALLY and contains NO sleeping accommodation.

If the INTERNAL floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval, providing that the building contains NO sleeping accommodation, and is either at least one metre from any boundary, or it is constructed of substantially non-combustible materials.

Complying with Building Regulations

Therefore in general, Garden Buildings do not need to comply with Building Regulations (other than Part P for Electrical works).

Part L (does not apply to buildings under 50m2 internal floor area per Regulation 21) takes account of the insulation qualities of walls, roof, floor, doors and windows, and new Building Regulations introduced in April 2014 impose stricter fabric U-Values for England and Wales of:

ENGLAND: Wall 0.18, Floor 0.13, Roof 0.13.

WALES: Wall 0.21, Floor 0.18, Roof 0.15.

The rules for Scotland known as Section 6 Regulations will also change in 2015.

Part P In the case of Garden Buildings Part P applies and any work is notifiable to the Local Authority. Work can be self-certified by an Electrical Installer who is registered as a competent person using a BS7671 electrical installation certificate for every job they undertake, with a copy given to the householder.