What are weep holes, and why does your brick wall need them?

If you look along the bottom of a brick wall you will often see small gaps in the mortar at regular spacing. Those are weep holes, and they are doing an important job even though they look like a mistake.

What they actually do

Most brick houses are built as a cavity wall: an outer skin of brick, a gap, then an inner wall. That cavity is there on purpose. Brick is not fully waterproof, and in driving rain some moisture gets through the outer skin and runs down the inside face. Weep holes let that water drain back out at the bottom, instead of pooling in the cavity. They also let the cavity breathe, so it can dry out and air can move.

Why they matter

Block the weep holes and the water has nowhere to go. Over time that leads to:

• Damp creeping into the inner wall and through to the inside of the house.
• Mortar and brick staying wet, which speeds up decay.
• Salt deposits and white staining on the brickwork.
• The right conditions for rot in nearby timber.

In Melbourne, with our wet winters and wind driven rain, a wall that cannot drain is a wall that stays damp.

Where you find them

Weep holes sit at the base of the wall and above openings like windows and doors, anywhere there is a damp proof course or a cavity tray collecting water that needs a way out. They are usually one open vertical joint every few bricks. Some are left as open joints, others have plastic vents or weep vents fitted.

Do not block them

This is the part that catches people out. It is tempting to fill or cover weep holes because they look like gaps that should not be there. Common mistakes:

• Rendering or painting over the base of the wall and sealing them.
• Building garden beds, paving or concrete up over them.
• Stuffing them with filler to keep insects out, with no proper vent.

If insects are the worry, use proper weep hole vents that let water and air through while keeping pests out. Do not just seal them up.

If yours are blocked or missing

If your wall has no weep holes, or they have been covered over, and you are seeing damp or staining inside, it is worth getting it looked at. Sometimes it is a simple matter of clearing or adding them, sometimes there is more going on behind the wall.

Not sure if your wall is draining the way it should? Send us a photo of the base of the wall and your suburb and we will tell you what we see.