Introduction

Planning permission and building regulations are often confused, and when investing any money in an extension, it is crucial to understand the difference and when each should be sought. You may require one, or other or both!

In a nutshell, planning permission determines if a building can be constructed or extended, while building regulations govern how such building works are undertaken. Both are managed by your local authority, who require a fee to process the work.

The following guide is primarily concerned with the rules for building works in England and Wales; those for Scotland and Ireland differ significantly. Regardless of your location in the UK, if you are in any doubt, always contact your Local Authority for advice and guidance, they are very helpful.

• If you do proceed with building works without suitable permission and signoff, your local authority can force you to alter the structure or to return it to its original state, at your own cost.

• Your local council authority

If you are dealing with a listed building or a property situated in a conservation area, the rules in these areas are considerably different, and your Local Authority will provide you with detailed information.

Alternatively, if you are on the receiving end of others proposed planning proposals, particularly in rural and 'green belt' areas, there are numerous groups and bodies willing to over advice (both practically and legally) should you require it. For example:

• Open Spaces Society

Planning permission

Planning permission is concerned with defending the public’s interest with regard to the look and use of the local environment to ensure that the character of the area is not adversely affected. Therefore, developments that do not affect the exterior of a property do not require formal planning permission, and some small external changes don’t either.

Planning permission must be sought if the intended use of a property is changing or being sub-divided, for example converting a garage into an office (habitable room) or dividing a house into flats. Building Regulations approval should also be sought to ensure that all requirements applicable to the new building purpose are met.

Anyone can apply for planning permission on any property, even if they do not own the land or building (although they must notify the owners). When an application is made, a notice will be published in the local paper and a notice must be displayed on the property so that the public can choose to view the plans and make comments.

If you have adhered to local guidelines, such as using only Cotswold stone in the Cotswolds, planning permission will be granted unless there are good reasons to refuse it, but if you are refused there is the right to appeal, although you should expect to make some modifications to the plans.

• You should receive a decision from the Local Authority within 8 weeks of application.

Any extension can proceed without planning permission if the following criteria are met:

• The area of land covered with buildings is less than half of the total area of the plot.
• The new building is no closer to, or remains at least 20m (66ft) away from, any highway (public road, footpath or bridleway) than the original building.
• No part of the new building stands higher than 4m (13ft 1½in).
• No part of the new building projects above the highest point of the original building.
• No part of the new building stands within 2m (6ft 7in) of any boundary.
• The volume of an extension to a terraced property is less than 50m³ (1,767 cubic feet) or less than10% of the volume of the original building, whichever is the greater, subject to a maximum of 115m³ (4,064 cubic feet).
• The volume of an extension to a semi-detached or detached property is less than 70m³ (2,474 cubic feet) or less than 15% of the volume of the original building, whichever is the greater, subject to a maximum of 115m³ (4,064 cubic feet).
• The original building is not listed or in a conservation area.

• Bear in mind that the volume of the original building is not necessarily the same as the volume of the current building, which may already have been extended and therefore will have used up some of the ‘permitted development limit’.

Building regulations

These requirements specify how a building should be constructed or extended to ensure that it is structurally safe, energy efficient, has adequate ventilation for it purpose and is protected against fire risks.

Once building work has started, a Building Control Officer from the Local Authority will visit the site at defined stages to inspect the work. He may require changes to be made to ensure the building satisfies the regulations, whereupon he will certify the work.

Building Regulations approval will ALWAYS be necessary where a new or wider opening is formed in an existing wall of the property. This is a structural alteration, since all walls contribute to the structural strength of a building, and if this is a significantly load-bearing wall (as opposed to a partition or stud wall), it is likely that an RSJ (Rolled Steel Joist or I-beam) will be required. A structural engineer will determine how big the RSJ must be, and a Building Control Officer will need to certify that a joist of this size has been correctly installed and is suitably fire protected.

An RSJ should be supported at either end by at least 25mm (1in) of remaining wall and should be positioned below the current ceiling, to form a square ‘archway’.

• Full guide to the building regulations

The Party Wall Act

The Party Wall Act 1996 particularly comes into force in terraced and semi-detached homes and blocks of flats, although detached homes may not be exempt, depending on where the boundary lines of the plot are drawn and walls are constructed.

Essentially, a ‘party structure’ is any wall, floor, foundation or other structure that sits astride the boundary of a property or is used to separate distinct properties.

If you plan to carry out work directly to a party structure (even if it doesn’t extend beyond the centre line of the structure), build across a boundary line or excavate near to a neighbouring building you must obtain WRITTEN CONSENT from the adjoining parties. You should give notice in writing to the adjoining owners at least two months before the work is due to commence, and they can request that you pay for an independent surveyor to review the proposed work and make any amendments necessary to protect the structural integrity of their property.

• It is highly advisable to hire a certified architect to draw up plans for your extension and submit them to the Local Authority on your behalf.

Their plans should account for local guidelines and the latest building regulations and they should have professional insurance should anything go wrong. Architects can also oversee and project manage building works for you should you so wish.

• The party wall act

Further information and useful links

• Making structural changes to your property
• Guide to conservatories
• Guide to loft conversions
• Guide to basements
• More building works topics

• Find an Architect near you
• Find a Chartered Surveyor near you

• Full government guide to planning permission
• Party Wall Act: Explanatory booklet and example notice letters