The caveat is that not all brick is the same. A 1970s common brick wall, a face brick wall with a hard glazed surface, and a hundred year old sandstock wall laid in lime mortar are three completely different jobs, and treating them all the same is how walls fail.
Preparation is most of the job
Whatever else happens, the wall has to be clean, sound and able to be keyed into. That means a full wash down to remove dirt, dust, moss and any efflorescence, raking out and repointing any failed mortar joints, and dealing with anything that has sealed the surface.
On smooth face brick with a hard fired surface we key the wall mechanically or apply a bonding slurry, because there is very little for render to grip on its own. On common brick, which is far more porous, the mechanical key is usually already there.
Old brick needs a softer mix
This is the mistake that damages heritage buildings across the Inner West and inner city. Old sandstock brick is soft and it was laid in lime mortar for a reason. The mortar was designed to be weaker than the brick, so that when the wall moves the mortar cracks rather than the brick.
Put a hard modern cement render over that wall and you have reversed the relationship. The render is now stronger than the brick, so when moisture and salt need to escape, they escape through the brick face instead, and the brick starts eroding behind an intact render coat. You do not see it until the render finally comes off and takes the face of the brickwork with it.
On old walls we go softer and more breathable, with a higher lime content and lower cement content. It is a different mix and it is the correct one.
Painted brick
Render does not bond to paint. If your brick has been painted, that has to be addressed before anything else happens, and it will affect the price.
There are two legitimate routes. Mechanically remove the paint, by grinding, blasting or a chemical strip, which gets you back to a bare porous surface. Or use a bonding bridge system specifically designed to be applied over sealed surfaces, which is faster and less messy but costs more in materials.
What is not legitimate is rendering straight over paint and hoping. We see the result of that regularly and it is always a complete redo.
Garden walls, boundary walls and piers
A lot of brick rendering in Sydney is not the house at all. It is the front fence, the boundary wall, the garden retaining wall or the letterbox pier. These are small jobs with a big visual return and they are often the first thing we do for a client.
One detail matters more on these than anywhere else. A freestanding wall gets weather on both faces and on the top, so the top has to be capped or the render has to be detailed to shed water. An uncapped rendered wall lets water straight into the top of the brickwork and it will push the render off within a few seasons.
