Most homeowners won’t need to acquire planning permission from the local authority to be able to modify or expand their loft space. However, there are specific requirements that must be met in order for your loft conversion to fall within Authorised Development.

For the official guide take a look at: http://www.planningportal.gov.uk/permission/commonprojects/loftconversion/miniguide

• A volume allowance of 40 cubic metres for terraced houses
• A volume allowance of 50 cubic metres for detached and semi-detached houses
• No extension past the plane of the current roof slope of the principal elevation that fronts the highway
• No extension to be higher than the highest part of the roof
• Materials to be similar in appearance to the existing house
• No verandas, balconies or raised platforms
• Side-facing windows must be obscure-glazed
• Any opening must be 1.7m above floor level
• Dormers are not allowed on a principal elevation that fronts a highway
• Roof extensions are not permitted in designated areas (including national parks, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites)
• Roof extensions, apart from hip to gable extensions, to be set back as far as practicable at least 20cm from the eaves.

If for some reason your property doesn’t fall within the allowed development regulations, it doesn’t automatically mean that you won’t be in a position to change or extend the property.

Planning permission is required if:

• You’re looking for a small, medium or large dormer in front of the house
• You want to use materials that happen to be different to those used on the current property
• Your house is within a designated area for instance a national park, Areas of Outstanding Natural Beauty, conservation area or World Heritage Site
• You wish to build past the plane of the current roof slope that fronts the highway
• You want to build to a higher level than the current roof
• You want to build a veranda, balcony or elevated platform