The purpose of the outer skin of a building is to keep moisture out of the house structure.
A damp proof course, in the brick veneer example shown below, has two purposes:
- It prevents moisture from the ground rising up through the external brick skin. (This moisture can cause effervescence which stains the brickwork)
- It ensures that moisture that penetrates the brickwork runs down the wall and is discharged to the outside through the weep holes.
The DPC, which is usually polyethylene, should be the full width of the brickwork. The other edge of the DPC should be fixed to the face of the bottom plate of the wall frame.
The drawing shows a DPC 75mm (one brick) above the ground. This is an absolute minimum and 150mm is preferred.
For other DPC details see this Clay Brick link.
For other similar posts see Construction