Weep holes in Retaining Walls

What are Weep Holes

retaining walls

Water accumulating within the side of the retaining wall can place stress on its structural integrity. If the overturning movement caused by the increased water pressure is more than the resisting vertical forces of the retaining walls, it will collapse. To address this weep hole is used.

These are small openings that are in a circular or rectangular shape used in retaining walls to drain excess water introduced into the structure by capillarity, leakage, or infiltration. It is usually provided with the help of sand drainage channels that allow them to function properly. The main function of the weep hole is to relieve the hydrostatic pressure acting on the retaining wall. They also prevent moisture from becoming trapped in the walls. For ventilation, these holes enable air to reach the back of the wall inside the wall cavity. It also helps reduce the occurrence of dry rot and dampness that typically builds up when moisture enters an unventilated space.

When are weep-holes needed in retaining walls?

If you are building a retaining wall structure below the water table then there is excessive water pressure on the wall structure, you need a weep hole. This additional hydrostatic pressure can be reduced by providing weep-holes at the bottom of these structures. The weep-holes are placed in the bottom of the retaining walls. 

Their dimensions need to be carefully designed to control surface tension. The number of weep-holes that need to be installed in a retaining wall structure depends on the maximum possible height of water accumulation or natural ground water table.

retaining walls

Advantages of Weep-holes in Retaining Walls

  1. Weep-holes are small openings or drains that are incorporated into retaining walls. They serve several important purposes and offer a range of advantages. Some of the advantages of weep-holes in retaining walls include:
  2. Water drainage: Weep-holes allow for the effective drainage of water from behind the retaining wall. They prevent the build-up of hydrostatic pressure, which can cause soil saturation, erosion, and potential structural damage to the wall.
  3. Alleviate water pressure: Weep-holes help to reduce the pressure exerted by water on the retaining wall. By providing an outlet for water to escape, they alleviate the pressure that can accumulate behind the wall.
  4. Prevent soil erosion: Weep-holes allow excess water to escape from the backfill or soil retained by the wall. This prevents water from saturating the soil, which can lead to soil erosion, destabilization, and potential collapse of the wall.
  5. Promote air circulation: Weep holes allow for air circulation behind the retaining wall. This helps to prevent the accumulation of moisture and promote the drying out of the surrounding soil, reducing the likelihood of mold or mildew growth.
  6. Control groundwater levels: By providing a drainage outlet, weep holes help to control groundwater levels behind the retaining wall. This is particularly important in areas with high water tables or areas prone to heavy rainfall, as it prevents excessive water from exerting pressure on the wall.
  7. Extend the lifespan of the retaining wall: Weep holes play a crucial role in maintaining the structural integrity of the retaining wall. By preventing water accumulation, soil saturation, and erosion, they help to extend the lifespan of the wall, reducing the need for frequent repairs or replacement.
  8. Overall, weep holes are a vital component of retaining walls as they provide effective water drainage, prevent soil erosion, control water pressure, promote air circulation, and contribute to the long-term durability of the structure.

Types of Weep-holes in Retaining Walls

Open Head Joint Weep-Holes

These head joints are spaced at regular intervals at the base of the cavity wall and are the easiest type of weep hole to construct. They are placed in the upper wall joint to drain water only from that point. These are also quite effective in vapourising water from the cavities. For this type of weep hole, a plastic drainage structure is also provided around the drainage holes to prevent rain and inserts from entering the holes.

Cotton Rope Wicking Weep-Holes

These weep-holes are created using ropes that are less than 12 inches long. One end of the rope is placed at the joint and the other end extends to the cavity wall. The water from the back of the wall is absorbed by the cotton and on the other side, it gets evaporated.

round weep holes

Tubes Weep Holes

The tubes in the weep holes tubes are created using hollow plastic or metal tubes [spaced around 16 inches from each other]. The drain of the pipe is installed at a slight angle to facilitate the flow of water through the pipe.

Corrugated Channel Weep Holes

These types of weep holes help to quickly drain off water from the multiple channels. It is installed at the bottom side of the bed joint of the mortar.


A retaining wall weep hole is a passage for water to escape a building envelope. Weep holes serve an important purpose in a building. The primary function of these Weep Holes is to provide ventilation for the internal cavity walls and prevent them from water damage. Discussed above are different types of Weep Holes available; you can choose any of them that best matches your needs.

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