What happens to unrendered walls?
Walls act as the foundations for the roof of a building and they shelter the occupants from the weather when it rains, snows, becomes windy etc. Hence, walls are important and need to be maintained.
If walls are not given a render coat, they will be damaged by frost and wind.
Pic A – porous brick
Pic B – what the porous brick looks like on close inspection
Notice that most bricks have small holes in them (they are called porous bricks) and it is these small holes that allow water from rain to penetrate the brick which leads to erosion. When water enters the interior of the brick and is subjected to extremely cold temperatures during Winter, the water solidifies and becomes ice which expands and makes the small holes bigger until the holes are large enough to form cracks and break the brick apart (see Pic C for a visual aid of th).
Pic C – weathering of brick by erosion
Pic D – a cracked brick wall due to erosion