Matching materials: what similar appearance really allows

The matching materials extension planning condition does not say identical. Class A of the householder permitted development rights requires that materials used in exterior work be of a similar appearance to those used on the exterior of the existing house, and a planning permission will usually carry a condition in similar terms or ask for samples. Similar appearance is a lower bar than a perfect match, and it is judged from normal viewing positions rather than from a builder's hand. Knowing that changes what you specify and what you argue for.

Where the similar appearance condition sits

Two separate places, and people conflate them.

If you are building under permitted development, the requirement is a condition attached to Class A in Part 1 of Schedule 2 to the General Permitted Development Order 2015. Materials used in any exterior work must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse. Conservatories are excluded from that requirement.

Note the word existing, not original. If the house was rendered twenty years ago, the comparator is the rendered house you see today, not the brick underneath.

If you have planning permission, the requirement comes from a condition on the decision notice. That will either approve named materials on the submitted drawings, or require samples to be submitted and approved before the relevant works begin. Read which one you have, because a condition requiring approval has to be discharged and a condition naming materials does not.

On land covered by article 2(3) of the Order, which includes conservation areas, National Landscapes, National Parks and World Heritage Sites, cladding an elevation is taken out of permitted development altogether. That is a separate restriction from the materials condition and it catches people who assume a like-for-like cladding job is covered.

Similar against identical in practice

Officers apply a common sense test. Would an ordinary person standing on the pavement read the new work as part of the same building?

That allows a good deal. A modern brick within the same colour range and a comparable texture will usually pass on a rear extension even if a bricklayer could tell the difference. It will not pass on a front elevation in a conservation area where the original is a handmade stock with obvious variation.

What fails is a change in character rather than a change in shade. A smooth wire-cut brick next to a soft sand-faced stock reads wrong at any distance. A machine-made concrete tile next to natural slate reads wrong from the street. And render over one bay of an otherwise brick elevation reads as a repair.

Where you cannot match, say so in the application rather than hoping. An officer told about the problem will engage with the solution. An officer who finds out on a site visit will issue a breach of condition notice.

Sourcing a brick match on an older house

Three variables, in order of importance: format, texture, colour.

Format is the one that catches everyone. Bricks laid before the mid 1960s are usually imperial, around 9 inches long by 3 inches deep, against a metric brick of 215mm by 65mm. Lay metric bricks alongside imperial and the courses will not line up at the junction, which produces a visible stepped joint up the whole height of the wall. Specialist suppliers stock imperial-sized bricks for exactly this reason, and the cost difference is smaller than the cost of getting it wrong.

Texture next. Handmade, stock, wire-cut and pressed bricks all catch light differently, and the difference shows most in raking sunlight on a long elevation.

Colour last, and with a warning. A brick that matches a hundred-year-old wall on the day it is laid will not match in five years, because the old wall carries a century of weathering the new one does not. Better to choose a brick that matches the underlying colour of the old work rather than its current surface, and accept a period of visible difference.

Reclaimed bricks are an option and they carry their own problems: variable frost resistance, old mortar on the faces, and quantities that run out halfway through. If you use them, over-order and have them checked.

Mortar colour and jointing

Mortar is roughly a fifth of the visible wall surface, and it is the detail most commonly ignored.

Match three things. The colour, which comes mainly from the sand, so ask the supplier for the same sand source used locally rather than a pigment. The joint width, which on imperial brickwork is often wider than modern practice. And the joint profile: flush, bucket handle, weather struck or recessed. A bucket handle joint next to a weather struck one is obvious even where the colours agree.

On a solid-walled house built before about 1919, the mortar should normally be lime rather than cement. A cement mortar is harder than the brick, which forces moisture and salts to evaporate through the brick face instead of the joint, and the result is spalling. Historic England publishes technical advice on traditional mortars, and a conservation officer will expect the specification to follow it on any listed or locally significant building.

Roof tiles, slates and weathering

Roofs are read from further away and the patterns matter more than the individual unit.

Natural slate against fibre cement is visible from the street because the surface reflects differently and the edges are cut rather than split. Clay pantiles and plain tiles weather to a colour that new stock cannot reach, and on a small extension the simplest answer is often to strip and reuse the original tiles on the visible slope, with new material on the hidden one.

Check the pitch before anything else. Many traditional coverings have a minimum pitch below which they are not weathertight, and a shallow extension roof that was drawn for a matching tile may have to change covering entirely. At that point a different material, honestly detailed, is a better answer than a compromised match. The related question of when a change of external finish needs consent in its own right is covered in the notes on rendering or cladding a house.

Sample panels and the materials condition

Where the condition requires approval, build a sample panel on site. A square metre or so, in the proposed brick, laid in the proposed bond with the proposed mortar and the proposed joint profile, is worth more than any number of product photographs.

Put it somewhere the officer can see it against the existing wall, leave it up until the works are complete, and photograph it. Submit the discharge application with the photographs, a product data sheet, the mortar specification and the panel location. Most authorities will deal with a well-presented materials discharge inside the target period.

Two practical points. Apply to discharge before the bricks are delivered, not after, because a refusal after delivery is expensive. And if the condition is worded to bite before any works begin, starting without discharging it can put the whole permission at risk rather than just the materials.

When a contrasting material is the better answer

Sometimes matching is the wrong objective. On a listed building or in a sensitive conservation area, a conservation officer may prefer a clearly modern extension in a frankly different material, so that the historic fabric stays legible and the new work is not a pastiche of it.

The same logic applies to a large extension on a small house, where matching brick can make the addition read as a botched enlargement of the original rather than as an addition to it. A contrasting but quiet material, set back behind a recessed link, often reads better.

Make the argument in your Design and Access Statement with elevations and a materials board, and relate it to the character of the group rather than to the single house. The same character reasoning governs the terrace-scale decisions discussed in the notes on chimney removal and the character of a terrace and on extending a house that has already been extended.

Enter your postcode on PlanScope to see which reports your project is likely to need. 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.