The materials of similar appearance condition explained
Breach the materials condition and the permitted development right disappears. What similar appearance means for brick, render, cladding and dormer cheeks.
The materials condition in Part 1 of the General Permitted Development Order requires that materials used in exterior work are of a similar appearance to those on the exterior of the existing dwellinghouse. It appears as condition A.3(a) for extensions and alterations under Class A, and as B.2(a) for roof enlargements under Class B. The word is similar, not matching, and the difference is where most of the argument sits. Get it wrong and the whole extension falls outside permitted development, because a breached condition means the development was never permitted by the Order at all.
That last point is worth sitting with. A materials failure is not a minor defect to be tidied up later. It removes the right.
Where the condition sits in the Order
The Town and Country Planning (General Permitted Development) (England) Order 2015 sets out householder rights in Schedule 2, Part 1. Class A covers enlargement, improvement or other alteration. Class B covers additions to the roof, which is how dormers are permitted.
Both classes carry a materials condition in almost identical wording. Class A adds the roof pitch condition at A.3(c), requiring the pitch of a two-storey enlargement to match the original house so far as practicable, and both classes carry the obscure glazing condition for side elevation windows above ground floor.
Separately, the limitations in A.1 restrict what can be built at all. On article 2(3) land, which means conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites, cladding of any part of the exterior with stone, artificial stone, pebble dash, render, timber, plastic or tiles is excluded from Class A entirely. That is a limitation rather than a condition, so in those areas the materials question often does not arise. The right simply is not there.
Similar appearance, not identical specification
Similar appearance is judged from the outside, as the building is seen. It does not require the same manufacturer, the same batch or the same age of brick, which would be impossible on a house built in 1935.
What it does require is that a reasonable observer would read the new work as belonging to the same building. A red multi stock against a red multi stock passes even if the shade differs slightly. A buff brick against a red one does not. A concrete interlocking tile against a plain clay tile is usually argued over, because profile and shadow line matter as much as colour.
Weathering is the fair point applicants make, and it cuts both ways. New brick will be brighter than a facade that has been out in the weather for ninety years, and councils accept that. A deliberately contrasting material chosen for design reasons is a different matter, however well it is detailed.
The practical test I would apply before advising a client: could you photograph the junction and have an officer accept, without explanation, that both sides are the same building? If the answer needs a paragraph, apply for permission.
The conservatory exception
Class A's materials condition excludes materials used in the construction of a conservatory. That is why a glazed and framed addition in white uPVC on a brick house can still be permitted development.
The exception is narrower than it is often treated. It covers the conservatory's own construction, not the works around it, and it does not turn any glazed box into a conservatory. Where a structure has solid walls, a solid insulated roof and is open to the house as a habitable room, the argument that it is a conservatory becomes thin.
Roof glazing rules have shifted in building regulations terms over the years, and a structure designed to meet Part L as a habitable extension is, in appearance and function, an extension.
Render, cladding and contrasting materials
This is the untidiest corner of the topic, and it deserves an honest answer rather than a confident one.
Outside article 2(3) land, rendering an existing house is capable of being an improvement or alteration under Class A. But the condition at A.3(a) applies to the materials used in any exterior work carried out under that class, and smooth white render is not of similar appearance to the brick it covers. Read strictly, the right permits the operation and the condition then defeats it.
Councils differ in how they handle this. Some accept full rendering of a whole house as permitted development on the basis that the finished building is uniform. Others take the strict reading. Both positions get defended.
Where a client wants to render, clad in timber, or introduce a contrasting material on an extension, the sensible advice is to apply for a lawful development certificate and get the position determined, or to apply for planning permission and argue the design on its merits. A certificate under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that proposed works are lawful.
Partial rendering is the weakest position of all. A rendered rear extension on an unrendered brick house fails the similar appearance test in almost any reading.
Roofs, dormers and what is visible
Class B carries the same materials wording, plus the requirement that the edge of the enlargement closest to the eaves is, so far as practicable, at least 20 centimetres from the eaves.
Dormer cheeks are where schemes come unstuck. Lead, zinc, tile hanging and render all appear on dormers, and whether each is of similar appearance depends on what is already on the roof and the elevation below. A tile-hung cheek on a tiled roof reads comfortably. A grey composite panel on a clay-tiled roof does not.
Flat roof coverings on single-storey rear extensions are treated more pragmatically, because a membrane laid behind a parapet is not visible from any public vantage point or from neighbouring windows. That is a practical accommodation rather than a stated exemption in the Order, so do not rely on it where the roof is overlooked from an upper floor next door.
Rooflights are not caught by the materials condition, though Class C has its own limits on projection.
Evidence a case officer will accept
- A materials schedule naming manufacturer, product, colour reference and finish for every external element.
- Photographs of the existing elevations taken in even light, with a sample of the proposed material held against the existing wall.
- A sample panel on site where the work is large or the match is contested, which some officers will ask to visit.
- Elevational drawings that annotate materials rather than relying on a hatch pattern.
- Where an older house has several brick types, a note saying which one the new work matches and why.
Submitting this with a certificate application is far more persuasive than submitting it after an enforcement officer has called. Our note on how previous extensions count against your allowance covers the other limitation that commonly bites at the same time.
When a full application is the safer route
If the design depends on contrast, apply. If the house is on article 2(3) land and the proposal involves any of the listed cladding materials, the right does not exist, so apply. If the existing house has already been extended in a different brick, the question of which exterior the new work should resemble has no clean answer, and a certificate application costs less than an argument about it later.
The classification questions around principal elevations and curtilage are worth checking at the same time, and our piece on curtilage and the principal elevation deals with those. The rear extension depth limits are the third thing to confirm before any of this matters.
Where an application turns out to be the right route, a planning statement that addresses design and materials against the local plan and any design guide does most of the persuading.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Does the materials condition require an exact brick match?
No. The wording is similar appearance, judged from outside as the building is seen. A slightly different shade of the same brick type passes. A different colour or a markedly different profile does not. New work being brighter than a weathered facade is accepted, because weathering is expected to close the gap over time.
Can I render a house under permitted development?
Outside conservation areas and other article 2(3) land, rendering can fall within Class A as an alteration, but the materials condition requires similar appearance and render over brick is not similar. Councils take different views on whole-house rendering. Apply for a lawful development certificate to settle it rather than relying on a reading.
Why are conservatories treated differently?
Class A excludes materials used in the construction of a conservatory from the similar appearance condition, which is why a glazed addition with white frames can sit on a brick house. The exception covers the conservatory's own construction only, and a structure with solid walls and an insulated roof is unlikely to qualify.
What happens if the materials condition is breached?
The development falls outside the Order entirely, because permitted development under Class A is granted subject to that condition. The work is then unauthorised and the council can take enforcement action, or require a retrospective planning application. It is not treated as a minor defect to be corrected by agreement.
Does the condition apply to flat roof coverings?
The condition covers materials used in any exterior work, so in principle yes. In practice councils take a pragmatic view of a membrane behind a parapet that cannot be seen from any public vantage point. Do not rely on that where the roof is overlooked from neighbouring upper floor windows.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.