This page provides practical guidance based on our project experience. It is not legal or planning advice. Planning rules are subject to change and vary by local authority. Always consult your local planning authority or a qualified planning consultant for guidance specific to your site and proposal.
Permitted development for householders
In England and Wales, homeowners have a set of permitted development rights — changes they can make to their home without applying for planning permission. For extensions, the rules cover the size, position, and height of the proposed addition. Timber frame is not a separate planning category: a timber frame extension is treated identically to a masonry or steel frame extension under permitted development. The construction method does not affect whether planning permission is needed; the size, position, and relationship to the existing building determine this.
For a single-storey rear extension, the key limits under Class A permitted development in England are: maximum projection of 3m beyond the original rear wall for a terraced or semi-detached house (4m for a detached house), maximum height of 4m at ridge (3m at eaves for structures within 2m of a boundary), and no extension forward of the principal elevation. Extensions that stay within these limits typically do not require planning permission, though a prior approval check is needed where the extension exceeds half the limits.
Wales has its own permitted development regime under the Town and Country Planning (General Permitted Development) Order 1995 (as amended for Wales). The limits differ from England in some respects. The maximum projection for a single-storey extension in Wales is 3m regardless of dwelling type. If your project is in Wales — which most of our residential work is — the Welsh rules apply.
When you do need planning permission
Planning permission is required for: any extension to the front elevation of the building; side extensions in some cases; two-storey rear extensions; extensions that exceed the height, projection, or footprint limits; properties where permitted development rights have been removed by an Article 4 direction; properties in conservation areas, National Parks, Areas of Outstanding Natural Beauty, or other designated landscapes; and listed buildings.
Permitted development rights are also removed for some properties as a condition of a previous planning permission — for example, a new-build house where the developer restricted future extensions to avoid over-development. If you are unsure whether your property has had its permitted development rights removed, check the planning history on the local planning authority’s website or make a pre-application enquiry.
Conservation areas
In conservation areas, permitted development rights are significantly restricted. Most external alterations to buildings — including extensions, cladding changes, and alterations that affect the appearance of the building from a public place — require conservation area consent or planning permission. The purpose of a conservation area designation is to protect the area’s special architectural or historic character, and the planning authority has discretion to resist changes that they judge would harm that character.
we have worked in conservation areas across Powys and Shropshire. Their experience is that oak framing is generally viewed sympathetically in conservation areas with a strong Welsh Marches vernacular tradition: it is a traditional construction method that uses local materials. The key to a successful conservation area application is designing with the designation in mind from the outset — understanding which character elements the conservation officer is protecting and how the proposed extension responds to them — rather than designing freely and then seeking consent for the result.
We can produce drawings and material schedules that support a conservation area application. For complex cases or where the application is contentious, a planning consultant with conservation experience is a worthwhile investment. We can make introductions to consultants we have worked with on previous projects.
Listed buildings
Listed building consent is required for any alteration to a listed building that would affect its character as a building of special architectural or historic interest. This includes extensions, alterations to structural elements, changes to windows and doors, and internal alterations that affect historic fabric — including replacement of structural timbers. Listed building consent is in addition to, not instead of, planning permission for any works that also require it.
Timber frame construction is often viewed sympathetically in listed building contexts because it is a traditional method that does not introduce new incompatible technologies into the fabric of the building. A timber-framed extension to a listed stone farmhouse has a better precedent in the listing officer’s experience than a steel and glass extension to the same building. This does not mean consent is automatic — it means the proposal starts from a reasonable position.
The materials specification for a listed building extension must be carefully considered. Conservation officers in Wales expect natural materials: lime mortar, natural stone or brick, natural Welsh slate, and uncoated timber — either left to weather naturally or finished with linseed oil or traditional oil-based treatments. We can provide a materials schedule and a written statement of significance to support a listed building consent application.
Building regulations
Building regulations are separate from planning permission. An extension can be permitted development (no planning permission required) and still require building regulations sign-off. The regulations cover structural safety, fire safety, insulation, ventilation, drainage, electrical safety, and access. For a timber frame extension, building control will want to see structural engineering calculations for the frame — demonstrating that the frame has been designed to carry the loads it will experience safely.
Citadel works with structural engineers who produce the calculations and drawings needed for building regulations submission. Building control inspects at key stages: foundations, structural frame, insulation, and completion. The frame-raising inspection is the most significant structural milestone. Citadel produces and fabricates to the engineer’s approved drawings, so building control inspection of the completed frame is straightforward.
our involvement in the planning process
our role is to build what they designed. They advise from their project experience, produce drawings that support planning and building regulations applications, and connect clients with structural engineers and planning consultants we have worked with successfully. They are not planners or planning consultants, and they do not provide formal planning advice. What they can do is ensure that the design they put on paper reflects what a conservation officer or planning officer would likely find acceptable in the specific local context — and they can give an honest view of how they have seen similar proposals receive.