Planning, Building Regulations and listed buildings, explained

Not always. Many single-storey rear extensions can be built under permitted development, which means no planning application is needed. In England the usual limits are 3 metres deep for a terraced or semi-detached house and 4 metres for a detached house, no more than 4 metres high, and no more than half the garden covered by extensions and outbuildings.

Permitted development does not apply to flats or maisonettes, is restricted in conservation areas and on listed buildings, and can be removed altogether by the council (an Article 4 direction) or by an earlier planning condition. Where an extension relies on permitted development, we usually recommend a Lawful Development Certificate so you have it in writing when you come to sell.

We check which route applies to your house before any design work starts.

Permitted development rights let you carry out certain extensions and alterations without a planning application, as long as the work stays within national limits on size, height and position. They cover many rear extensions, some loft conversions, porches and outbuildings.

The rules are detailed and change from time to time, and they work differently in conservation areas, the Cotswolds National Landscape and on listed buildings. We confirm the position for your property and, where it helps, apply for a Lawful Development Certificate.

Planning permission is about whether you can build something at all: its size, appearance and effect on neighbours and the area. It is decided by the local council's planning department.

Building Regulations approval is about how it is built: structure, fire safety, insulation, drainage, ventilation and access. It applies to almost all extensions, loft conversions and structural alterations, whether or not planning permission was needed, and is checked by the council's building control team or a registered building control approver.

Most projects need both, each with its own set of drawings, and we prepare and submit both.

Yes, but you will need listed building consent for any work that affects its character, inside or out. That includes things that might seem minor, such as replacing windows, removing internal walls or changing joinery. Carrying out work to a listed building without consent is a criminal offence, so it is worth getting right.

An application is usually supported by measured drawings, a heritage statement explaining the building's significance and how the work affects it, and details of materials and repairs. We have spent most of our working lives on listed and historic buildings and prepare all of this in house.

Councils aim to decide householder applications and listed building consent within 8 weeks of the application being validated, and larger applications within 13 weeks. Validation itself can take a week or two, and busy councils sometimes run over.

Allow two to three months from submission for a typical extension in Bristol, Bath and North East Somerset, North Somerset, Somerset, Wiltshire or the Cotswolds. Getting the application complete and well presented first time is the best way to avoid delays.

No. There is no legal requirement to use an architect for an extension, loft conversion or new house. "Architect" is a protected title for people registered with the Architects Registration Board, but the drawings, planning application and Building Regulations package can be prepared by an architectural technologist or designer.

What matters is experience with the type of building and the council concerned. We have designed homes since 2000, with a long background in conservation work.

A measured survey records the existing building accurately: floor plans, elevations, sections and levels. Every set of planning and Building Regulations drawings is based on it, so errors at this stage carry through to the build.

For most extensions and alterations, yes. We carry out the survey ourselves at the start of the project, and on older buildings we record the condition of the fabric at the same time.

Usually, yes, if the work involves removing walls, new openings, steel beams, new foundations or a loft conversion. Building control will need structural calculations before they approve the work.

We appoint and coordinate the engineer for you, so their design is drawn into the Building Regulations package and your builder works from one set of information.

If you are building on or near a shared wall or boundary, or excavating for foundations close to a neighbour's building, the Party Wall etc. Act 1996 usually requires you to serve notice on the neighbour before work starts. Depending on the work, the notice period is one or two months.

If the neighbour agrees, the work can go ahead. If not, surveyors are appointed to agree a party wall award. We identify whether the Act applies at design stage and coordinate with a party wall surveyor where needed.

It depends on the size of the project, the condition and age of the building, and which stages you need, for example planning drawings only or the full service through to completion.

After a conversation about your project, we send a written fee proposal setting out exactly what is included and what it costs, before any work starts. There are no hidden extras.

For a typical extension: around two to six weeks for survey and design, two to three months for planning, and three to six weeks for Building Regulations drawings, engineering and tender. Some of this can overlap.

Listed buildings and new houses usually take longer. We give you a realistic programme at the start, and update it as the project moves.

Conservation areas, such as Clifton in Bristol, much of central Bath and many Cotswold villages, have tighter planning controls. Some work that would normally be permitted development needs a planning application, for example side extensions, some roof alterations and external cladding. Most demolition also needs permission.

The council will expect the design to preserve or enhance the character of the area, and a short heritage statement often helps the application. We work in conservation areas regularly and design with that in mind from the start.