Retaining walls are structures that hold back soil and avoid corrosion. They are typically used in construction projects and remodelling to create smooth surfaces on inclined planes. A crucial aspect of retaining walls is adding weep holes, which are small voids purposely designed into structures, especially in retaining walls, to allow controlled water drainage. These inconspicuous holes help preserve the structure’s integrity and the lasting strength of retaining walls. This blog explores the functionality of weep holes, their types, and their significance in letting water drain from behind the wall and preventing harm to the structure.
What are Weep Holes?
Weep holes in retaining walls enable water to escape from small voids. They mainly help eradicate water build-up in the soil, which can cause improved lateral pressure and ultimately cause the structure to fail. These holes are located at regular intervals near the base of retaining walls. In taller walls, especially in older structures, you might find extra rows of weep holes positioned higher up to enhance drainage.
Functioning of Weep Holes
Retaining walls are equipped with weep holes to drain extra water introduced into the structure by capillary, seepage, or infiltration. When water plastering is used, these holes are required, and the extra water pressure on the structure exceeds the saturated and earth pressures.
Case 1: No Weep Holes, Water Table is Below the Structure
Weep holes are unnecessary if the water table is below the structure. Because the structure is above the water table, the earth pressure is considered when designing it.
Case 2: Structure Water Table is Higher Then Forget About Weep Holes
When water and soil are mixed, the saturated pressure—or earth pressure—transforms into a submerged load, which is lower than saturated pressure but higher than saturated pressure. Remember to consider soil and water pressure when designing this type of structure.
Case 3: Weep Holes Are Installed, and The Water Table Is Above the Structure
While the structure includes weeping holes to help with drainage, it is significant to recognise that the water table can still rise above these openings. These weep vents are intended to release the pressure caused by water, allowing it to escape through these voids. A crucial factor to consider is the height at which the holes are placed. The position of these holes affects water pressure on the structure; the higher they are, the greater the pressure.
Types of Weep Holes in Retaining Walls
Open Head Joint Weep Holes
Open head joint weep holes are regularly spaced at the cavity wall base to allow moisture to evaporate. These holes are created in the upper joint for extracting the extra water. A plastic drainage structure is added around the drain voids to prevent rainwater and insects from entering the holes.
Cotton Rope Wicking Weep Holes
Weep holes of this type can be made using ropes less than 12” in length. One rope end is positioned at the joint, while the other extends into the cavity wall. The cotton material absorbs the water from behind the wall, evaporating to the other side.
Tube Weep Holes
Tube weep holes are created in retaining walls by placing hollow plastic or metal tubes 16″ apart. Gravel is installed to prevent water flow from the blocked drain.
Corrugated Channel Weep Holes
These types of weep holes are designed using modern technology, which can pump extra water and extract it from various channels. These weep holes are installed at the base of the mortar’s bed joint.
Pros and Cons of Weep Holes
Weep holes are voids in walls that help with drainage and ventilation. They are useful for structural integrity, but they also have some drawbacks.
Pros
Weep holes can:
- Help prevent water build-up behind a structure and avoid structural damage
- Help with ventilation, which can avoid mould and mildew.
- Reduce the water pressure behind a wall, preventing structural damage.
Cons
Weep holes can:
- Become blocked with algae, plants, mud, leaves, and pests, which reduce their efficiency.
- Still enable water to infiltrate in extreme weather conditions
- Provide an entry point for pests
Bottom Line
Weep holes are significant in retaining walls’ latest construction, functionality and durability. By enabling the water extraction from the structure, they offer protection against multiple construction and appealing issues. They ensure the retaining walls’ solidity and minimise maintaining structures’ structural integrity for an extended period.
Remember that appropriate design, placement, and sustainability of these voids are necessary for successful retaining projects, making them vital in construction and engineering.
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