Comparing Brick Options for Traditional House Extensions

Why the Brick You Choose Matters More Than You Think

A well-built extension can still look like a bolt-on if the brickwork doesn't sit comfortably with the original house. Two walls of different brick sitting side by side will read as two buildings, however neat the workmanship. The aim isn't a perfect replica — that's rarely achievable with new brick, and old walls are never uniform anyway — but a seamless join that the eye accepts without pausing.

The most common mistake is choosing a brick from a showroom panel under fluorescent light, or simply accepting whatever the local merchant has in stock. Matching takes a bit of detective work: colour, texture, bond pattern and mortar mix all pull their weight, and getting three out of four right still leaves a visible seam.

Reading Colour Properly

Look at the existing wall in three different lights before you commit: flat midday, low evening sun and dull overcast. Colour shifts dramatically. What looks like a rich red at noon can read as dull orange in shade, and a wall that seems uniformly buff usually isn't.

Stand back and study twenty or thirty bricks, not one. You're looking for a range: the base tone, the percentage of darker or lighter units, and the occasional burnt header or pale fleck. A brick that matches a single sample brick but lacks that variation will look flat and obviously new.

Brick tinting, where a permeable dye is applied after the wall is built and cured, is widely used on heritage and extension work and can take a new brick a shade or two closer to its older neighbours. It's not a substitute for choosing sensibly, but it's an excellent final adjustment.

Texture and Surface Finish

Under the same colour name you'll find bricks that behave very differently on the wall. A wirecut brick has sharp arrises and a slightly ridged or smooth face; a stock brick is soft, sandy and gently creased; a sandfaced or rusticated brick offers a coarser, more grainy surface.

A useful trick is to look at the wall in raking light — early morning or late afternoon. Texture that vanishes head-on becomes obvious when the sun grazes the surface. If the existing wall has a soft, crumbly face and you introduce crisp new wirecuts, the join will show even if the colour is spot on.

Reclaimed bricks offer instant age and texture, but they vary in size and composition, need more mortar to lay, and are considerably more expensive. Reproduction and blended new bricks — often sold as regional blends with names tied to a clay or county — tend to be the most practical middle ground.

Bond Pattern and Coursing

Measure before you buy. Take a tape to the original wall and measure ten courses, then divide by ten. Older brickwork is often imperial, with courses of 75mm or more, sometimes irregular. If your new brick plus a standard 10mm joint gives a different course height, the horizontal lines will drift out of alignment across the extension — and that mismatch is far more noticeable than a slight colour difference.

Bond matters too. Stretcher bond, English bond, Flemish bond and garden wall bond all produce different patterns across the wall face. An extension laid in stretcher bond against an English bond original will look wrong even if every brick is perfect. Also note the details: quoins, plinth, soldier courses over openings, and the depth and shape of reveals. These are cheap to copy and expensive to ignore.

Where the new wall meets the old, the bricklayer should tooth into the existing work properly rather than simply butting up to it, so the two read as a single fabric.

Mortar: Half the Visual Story

It's easy to focus on bricks and forget that mortar covers roughly a fifth of the wall surface. Get the mortar wrong and even excellent bricks look off. A hard grey cement mortar next to a soft, creamy lime mortar on an older house is immediately obvious.

• Sand colour drives the mix — sharp yellow building sand and red sand produce very different results.
• Binder type matters, but so does appearance: a lime-rich mix can be replicated in look on a modern extension where a stronger mix is needed structurally.
• Joint profile should match: struck, bucket handle, weatherstruck and recessed joints all cast different shadows.
• Joint depth should be consistent with the original, usually 8–10mm.

Always ask for a sample panel of a metre square or so, built in the proposed brick and mortar, and leave it to dry for a week before judging it against the house.

Sourcing, Spares and Letting It Weather

Reclamation yards are worth a visit for period properties, but buy the full quantity plus at least ten per cent spare before you start — batches disappear. Specialist brick matching services can survey the existing wall and recommend a blend, which is money well spent on a prominent elevation.

Order well ahead: a special blend can take six to twelve weeks. When the wall is up, don't seal it. Brickwork needs to weather, and a new extension usually settles into its surroundings within two or three years. Keep a few spare bricks in the garage for future repairs, and don't be tempted to pressure-wash the join in the meantime.