How to match old brickwork on an extension

Matching old brickwork is rarely a question of finding the same brick. Clay sources close, brick sizes changed across Australia when the country went metric, and decades of weathering have altered the wall you are matching to. What usually decides whether a junction reads well is the mortar and where you put the join — not the brick itself.

This is one of the few parts of an extension where the outcome is visible from the street forever, and it is routinely left until the bricklayer is standing on site asking what to order.

Most of the guidance available online is British, and it describes solid brick walls, lime mortars and imperial stock bricks. Australian houses from the 1950s onward are overwhelmingly brick veneer — a single skin over a timber or steel frame — and the brick sizes here changed in a way they did not in the UK. The principles carry across; the specifics do not.

Why is it so hard to match old bricks?

Clay is a local material. Brick colour comes from the chemistry of the clay it was made from and the temperature it was fired at. Brickworks drew from local pits, and a great many of those pits and works have closed. A brick made in 1962 from a clay seam that no longer exists cannot be reproduced, only approximated.

Firing varied. Older kilns produced more variation within a single batch than modern tunnel kilns do. That variation is part of what an old wall looks like — a uniform modern brick reads as flat against it even when the average colour is right.

The wall has weathered. Forty years of UV, dust, rain and pollution changes the face of a brick. Arrises soften, colour flattens, and organic growth and salts alter the surface. A new brick that genuinely matches the original as it left the kiln will still look conspicuously new beside it.

Texture is half the impression. Wirecut, pressed, dry-pressed and tumbled bricks all catch light differently. A colour match with the wrong texture rarely reads as a match.

Have brick sizes changed in Australia?

Yes, and this is the part that catches people out, because it is not a matter of taste. It is geometry.

Australia converted to metric during the 1970s, and the standard metric brick settled at 230 x 110 x 76 mm. Before that, bricks were made to imperial dimensions, and those varied by state, by works and by era — Federation and colonial-period bricks vary more again.

The practical consequence: if your house predates metrication, the courses will not line up. A small difference in brick height compounds with every course, so by the time you are a metre up the wall the beds are visibly out.

You have three ways to deal with it. Adjust the bed joints — mortar joints can absorb a little difference, but only a little, and joints that are noticeably thicker or thinner than the original look worse than the mismatch you were trying to hide. Cut the bricks, which is slow and shows on the cut face. Or break the wall — put a deliberate vertical junction between old and new so the two coursings never have to align.

The third option is almost always the right one, and it needs to be a design decision made early rather than a fix improvised on site.

Where do I find bricks that match?

Start with the bricks you are about to demolish. This is the best source and the most frequently overlooked. Forming an opening into the existing house means removing brickwork, and those bricks are a perfect match by definition. Set them aside carefully, clean them, and use them on the most visible new face — the front return, the corner, whatever the street sees. Use new brick where it will not be compared.

Say this to the builder before demolition, not after. Bricks removed with a jackhammer and put in a skip are not recoverable.

Brick matching services. Several Australian firms specialise in identifying and sourcing matches from salvage stock and current ranges. Send them a brick, not a photograph — colour cannot be judged from a screen.

Demolition and salvage yards. Genuine period bricks, though stock is unpredictable and you may need to buy what is available rather than what you wanted.

Manufacturers' heritage ranges. Most Australian brick makers produce ranges aimed at matching older housing stock. These are made to current metric sizes, so they solve colour and texture but not coursing.

The house itself, elsewhere. A rear wall, an old outbuilding, a chimney being removed, or a section being rendered anyway can all yield matching stock.

Does the mortar matter as much as the brick?

More, usually. Mortar joints make up a significant share of the visible wall face, and they are the element most often ignored.

Colour. Mortar colour comes largely from the sand. Local sands vary, and the grey cement mortar used today looks nothing like the softer, warmer lime-rich mortars of older buildings. A perfect brick match with the wrong mortar colour will still read as a patch.

Profile. Ironed, raked, flush, weathered, bucket-handle — the joint profile changes how the wall catches light and is instantly visible when it changes mid-wall. Match the existing profile, and make sure the bricklayer has actually looked at it.

Width. If brick sizes differ, joint width becomes the compensating variable, which is another reason a deliberate break beats trying to blend.

Strength, on older walls. This matters beyond appearance. Older, softer bricks were laid in lime mortar that was intended to be weaker than the brick, so movement and salt damage were taken up by the joint rather than the brick face. A hard modern cement mortar reverses that relationship, and the brick fails instead. On a genuinely old wall, mortar specification is a technical question worth asking about rather than assuming.

Build a sample panel. A small panel, laid with the proposed brick and mortar and left to weather for a few weeks, tells you more than any amount of discussion. It costs very little and it is the only honest test.

What if I cannot match them at all?

Then stop trying, because a near-miss is the worst outcome available.

A wall that is obviously two different bricks reads as a considered decision. A wall that is almost the same brick reads as a mistake, and the eye finds it immediately. This is the single most useful principle in the whole exercise.

Deliberate contrast. A clearly different brick, chosen to complement rather than approximate, with a clean junction between the two.

Render the new work, leaving the original brick exposed. Common, and it reads as an addition rather than a failed match.

Render everything, which unifies the whole building but is a substantial commitment and loses the original face permanently.

Change material entirely for the addition — cladding, timber, or a lightweight system. This is the contemporary approach and it removes the matching problem rather than solving it.

Express the junction. A recessed vertical shadow line where old meets new, so the change is framed rather than hidden.

Where should the join between old and new sit?

Wherever the eye does not naturally travel.

At an internal corner or a change of plane, where the shadow does the work for you.

Behind a downpipe, a column or planting, which is a legitimate design move rather than a cheat.

At a setback. Recessing the extension slightly from the existing facade creates a natural break, and it is the reason so many well-resolved extensions step back from the original front wall.

Not in the middle of a flat street-facing elevation, which is the one place it will always be visible.

There is a structural reason to think about this at the same time. Two structures of different ages move independently, and masonry needs articulation joints to accommodate that movement — otherwise the wall cracks along the line of least resistance, which is usually the junction. Putting the deliberate visual break in the same place as the movement joint solves both problems with one detail.

Common questions

Will new bricks weather to match over time?

Partly, and never completely. New brick will dull and pick up dirt, which narrows the gap. But the two will always be at different points in that process, and a brick made from different clay will not age along the same path. Plan for the match you have on day one, not the one you hope for in a decade.

Can bricks be stained or tinted to match?

Yes. Proprietary brick staining systems exist and, applied well, can shift colour convincingly. Results vary with the brick and the operator, it is a specialist job, and it is not reversible — so ask for a sample on a spare brick from your own wall before committing to an elevation.

Should I clean the old brickwork first?

Test before deciding. Cleaning can reveal a truer colour that matches new brick far better than the dirty face did, which occasionally solves the problem outright. But aggressive cleaning damages older, softer brick and can trigger salt problems — see what efflorescence on brickwork is telling you. Clean a small hidden area first and look at it wet and dry.

How many spare bricks should I order?

Order the full quantity plus wastage in a single batch. Brick colour varies between firing runs, so a top-up order months later may not match the bricks you have just laid, let alone the original wall. Keep whatever is left over.

Does the bricklayer choose the mortar?

Often by default, which is why it is worth raising. Ask what sand and mix are proposed, ask for the joint profile to be matched to the existing, and ask for a sample panel. None of that is an unreasonable request and most bricklayers would rather be told before they start.

Is a visible junction a defect?

Not in itself. Unless the contract specified a match, a difference between old and new brickwork is generally a design outcome rather than defective work. If matching matters to you, it belongs in the scope of works in writing, before anyone orders anything.

Where to go next

Brickwork is the most visible junction between old and new, but it is not the one most likely to cause you trouble.

Read next: how a new roof ties into an existing one — the junction that actually leaks — or what order trades come in on a renovation to see where brickwork sits in the sequence. Or start at Renovations & Extensions for the wider picture.

The decision that matters most gets made before demolition: keep the bricks you are about to knock out.