The top surface of the sill must be sloped. This is often called a "wash." A flat sill allows water to pool, which leads to saturation and leaks.
Here’s a full description, suitable for construction drawings or a spec section. This covers a typical through-wall flashing & weep system for a brick veneer over a wood or steel stud backup.
These are the industry standard for durability. Because they are a single piece of material, there are no joints to fail. brick sill detail
A small groove or metal edge on the underside of the projecting sill that breaks the surface tension of water, forcing it to drop to the ground rather than "wicking" back toward the wall. Common Brick Sill Orientations
The visible sill is only half the story. What happens behind the brick is what prevents a lawsuit. The top surface of the sill must be sloped
This detail uses bricks turned vertically (on edge) to form the sill. It creates a classic, heavy look often seen in Colonial or Craftsman style homes.
When rain hits a window, it runs down the glass and onto the sill. Without a proper projection and slope, that water sits on the brickwork or runs directly back into the wall. Masonry is porous; it absorbs water. If water is allowed to pool or track inward, freeze-thaw cycles will eventually destroy the brick and the structural components behind it. This covers a typical through-wall flashing & weep
A high-performance brick sill is more than just a row of bricks. It is a system of integrated parts:
A sill is essentially a roof for your wall. Beneath the sill material, you must install through-wall flashing. This membrane catches any water that gets through the brick or mortar and directs it to the weep holes. Without this, water saturates the wall cavity.