The similar appearance condition and matching brick

Part 1 of Schedule 2 to the General Permitted Development Order 2015 attaches a condition to most householder extensions: the materials used in any exterior work must be of a similar appearance to those used on the exterior of the existing house. That is the whole of the materials similar appearance permitted development test. It says similar, not identical, and it is about appearance rather than specification. A brick that is the same colour, size and texture from three metres away satisfies it even if the manufacturer and the clay are different.

The condition is also the most common reason a householder gets a letter from enforcement about an extension that was otherwise within the limits.

What the condition actually says

The wording applies to exterior work under Class A, with a carve-out for a conservatory. Similar conditions attach to roof enlargements under Class B and to the upward extension classes.

Two points follow from the drafting. First, the comparison is with the existing house, not with the street, the neighbours or a council design guide. A pebble-dashed semi can be extended in pebble dash even if every other house on the road is brick. Second, the condition is absolute: breach it and the development is not permitted at all, so the whole extension becomes unauthorised rather than just the offending wall.

Breach also happens by accident more often than by design. A builder substitutes a brick because the specified one has a 14-week lead time, nobody tells the owner, and the result is a wall two shades lighter than the house.

Similar appearance, not an exact match

An exact match is rarely possible. Bricks weather, colours run out, and a 1930s multi stock has no current equivalent. Councils and inspectors accept that, and look at whether the finished work reads as part of the same building.

What usually passes:

• A current brick chosen for colour, texture and format against a cleaned sample of the existing wall.
• A reclaimed brick of the same type, laid in the same bond with a matching mortar colour and joint profile.
• Tiles of the same profile and colour range as the existing roof, where the original is no longer made.
• Render of the same finish and colour on a rendered house.

What usually fails:

• A brick of the right colour but the wrong format, so the coursing does not line through.
• A smooth machine-made brick against a sanded or textured original.
• A grey or buff mortar against a lime or dark mortar, which changes the appearance of the whole wall more than the brick does.
• Trying to match by name rather than by sample.

Mortar is the one people miss. Get the brick right and the mortar wrong and the extension still reads as new, because the eye reads the joint pattern before it reads the brick.

Render, cladding and timber on a brick house

A contrasting material on a brick house breaches the condition under Class A, and the practical answer is usually one of three.

Apply for planning permission for the extension you want, which lets the council assess the design on its merits. A well-designed timber-clad rear extension on a brick house is often approved, and the application fee for a householder development is modest compared with the cost of getting it wrong.

Or keep the contrasting material inside the conservatory exception, which only helps if the structure really is a conservatory.

Or confine the contrasting element to an elevation and a scale the council is unlikely to pursue, which is a risk-management choice rather than compliance, and one worth taking advice on before building.

Where the house itself is already mixed, say brick at ground floor and tile hanging above, you have more room. The condition compares against the exterior of the existing house as a whole, so a materially present existing finish is a legitimate reference.

Roofs, ridge lines and verge detail

Roof work is judged the same way, and the details that give it away are not the tiles.

The ridge line is the first. A new roof set 50 millimetres above the original ridge, or with a different ridge tile profile, reads immediately. The verge is the second: a flush mortar verge against a dry verge system with a plastic end cap changes the edge of the roof.

Then the plane. An extension roof pitched at 32 degrees against an original at 40 looks like a different building regardless of covering. Where the geometry has to change, matching the covering becomes more important rather than less.

Rooflights are outside the materials condition but have their own limits on projection above the plane of the roof slope, which is a separate matter from appearance.

The stricter position on designated land

On article 2(3) land, meaning conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites, Class A does not permit the cladding of any part of the exterior with stone, artificial stone, pebble dash, render, timber, plastic or tiles. That is a flat prohibition, not a similar-appearance question.

So re-rendering a rendered house in a conservation area under Class A is not permitted development even though the appearance would be identical. It needs an application. Side extensions and two-storey rear extensions are also excluded on that land, and an Article 4 direction may have removed more.

Check the designation before you design. The council's online mapping and the national planning data service will both show conservation area boundaries, and an Article 4 direction will be listed on the authority's website.

Outbuildings sit differently

Class E, which covers outbuildings and garden buildings within the curtilage, contains no materials condition at all. A black timber garden office behind a red brick house is unaffected by appearance rules under that class, provided it meets the other limits including the fifty per cent curtilage test and is for a purpose incidental to the enjoyment of the dwellinghouse.

That difference is worth using. A detached studio can be a different material from the house. An attached extension cannot.

Recording what you used

The burden of showing that works were permitted falls on the owner when a question is raised, often years later at sale. Keep the evidence while it is easy to get.

1. Photograph the existing wall before works, including a close-up with a scale.
2. Keep the brick and tile delivery notes, the manufacturer's name and the product reference.
3. Keep a sample brick and a note of the mortar mix and joint profile.
4. Photograph the completed work in daylight from the same positions as the before shots.
5. If there is any doubt, apply for a certificate of lawfulness.

A Lawful Development Certificate is the only formal way to confirm that works are lawful. You can apply under section 192 of the Town and Country Planning Act 1990 for proposed works, which is the less expensive and calmer route, or under section 191 for works already built. Where the certificate application needs a written case, a short Planning Statement setting out the class relied on, each limit and condition, and the evidence for each, is what the officer is looking for.

And if a council officer has already raised the materials point, get the samples photographed before anything is cleaned or repointed. The evidence disappears quickly once a wall is washed down. Enter your postcode on PlanScope to see which documents a householder application would need if you decide to apply instead.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope produces AI-assisted draft reports for planning applications, and reports should be reviewed before submission. PlanScope does not guarantee planning approval.