Bricks can last over 100 years or more without repair. Unfortunately, the same isn't true for the mortar between bricks. Overtime this mortar can deteriorate, crack, come loose, and completely fallout. With the mortar damaged moisture can now enter these joints allowing for the bricks to become saturated with moisture. When bricks freeze with moisture inside them they will start to crack and then the faces of bricks will fall off and eventually the brick will crumble. Whole brick replacement is now necessary, costly, and matching bricks next to impossible. To avoid these costly repairs damaged motor needs to be repaired. This process is called tuck pointing and involves replacing the mortar.
Damaged mortar can also allow for moisture to enter behind the brick. If the brick wall has excessive mortar squeeze out on its back side then water can’t travel down easy to the weep holes. This can lead to rotting of wood sheathing behind the brick.
If the brick wall lacks weep holes and a rain screen then the potential for rot is even greater and unfortunately many homes are missing one or both of these components. That is why mortar joints can be so critical.
Missing flashing on top of a half brick wall is another major source of rotting behind brick. Unfortunately some builders failed to install this flashing and relied solely on caulking. Eventually all caulk will break down and fail and in this case the results can be severe rotting behind the brick. Large amounts of brick removal is usually needed to make repairs.
A broken or poorly pitched gutter, or missing flashing allows for excessive amounts of water to splash against a focused area of brick. This can lead to damaged mortar and brick in these areas. Again brick replacement is usually needed.