Weeping holes are generally found in the bottom row of bricks around your home, usually every third brick.
Some inexperienced masons fill them in, thinking they’ve found another hole, when they’ve been asked to repair other holes.
Weeping holes provide a run-off point for moisture that condenses behind the brick wall in the one inch air space that is required by law.
Weeping holes also allow the air behind the bricks to interact with the outside air, keeping the humidity levels even. When the holes are blocked and the air inside gets too humid, the moisture begins migrating through the bricks, carrying mineral salts to the surface. This result is called Efflorescence. It’s near impossible to get rid of, although you can try repeatedly soaking the outside wall to wash away the exterior salts, and you do have to solve the cause of the problem.
So don’t let your landscaper build a stairway or patio structure that covers the weeping holes, they’re important to you. And replacing the bottom row of bricks is tricky and therefore expensive.