Do you need drainage behind a retaining wall? Yes, which means you need backfill too. This backfill is the soil that's located in the first 12 inches of space right behind the retaining wall in order to have proper drainage, and it can be either gravel or crushed stone.
Retaining wall drainage is essential to building a good retaining wall. During the wall's construction, a drainage system is built in to drain water that is absorbed by the soil behind the wall.
Dig A Trench To Outline The Space
Ensure the trench is wide enough to support both the retaining walls as well as any plants or flowers that will be added. Keep in mind that the fill dirt will act as a base for the entire feature, meaning any wall layers and plants should have a layer of fill dirt underneath it.
Don't Forget To Backfill Behind Your Retaining Wall
Neglecting to backfill properly can lead to reduced support, increased pressure on the wall, and the possible collapse of the wall.
Correct drainage is one of the essential elements to focus on when building a sleeper retaining wall, ensure that there is a sufficient gap behind the wall to install all necessary drainage before you commence wall construction.
Base Material for Stability
The foundation of any retaining wall is as significant as the visible structure itself. The base material, typically a type of gravel, is essential for establishing a strong and stable base.
Plan to backfill the wall with well-draining gravel or sand. Higher walls or areas with soil that stays wet may need a drainage pipe. Keep in mind that clay soil retains water and sandy soil drains too easily. You'll need a well-draining soil mix behind your landscape retaining walls.
With the permission of both property owners, a retaining wall can be built on property lines. But it's worth noting that the two parties still have responsibility for any of their actions that destabilises the wall's structural integrity.
Even for a 2-foot retaining wall, there are benefits to adding a footing: Enhanced Stability: A footing provides additional stability, reducing the risk of settling or tilting over time. Improved Drainage: Footings can include drainage features, preventing water buildup behind the wall that could weaken it.
Soil saturation is the most common external factor that causes retaining wall failure, but there are many ways to prevent it.
Rules of thumb commonly used by designers to establish the geometry of the wall include (refer to diagram): Base width = 1/2 to 1/3 of the height of the wall. Base thickness = 1/8 of the height of the wall but not less than 12 inches. Stem thickness = 6 inches + ¼ inch for each foot of wall height.
In most dry stone walls, water flows freely through them, so a drain pipe part way up the back is utterly useless. The cut stones in this wall fit tightly enough that water penetration will be slow, making it more imperative that there is good drainage.
As per the Code- IS 456 : 2000 Clause 20.1, the stability of the retaining wall against overturning should be ensured that resisting moment should not be less than 1.4 times the maximum overturning moment. If the dead load provides restoring moment , then as per code 90% of the dead load should be taken into account.
For proper drainage you need at least 300 mm of gravel or similar material directly behind the wall. If you're planning on landscaping behind the wall, allow for at least 150 mm of topsoil above the gravel.
Hydrostatic Pressure and Wall Failure
When water isn't properly drained, it can accumulate behind the wall, exerting pressure on the structure. This pressure can prompt the wall to shift, crack, or even collapse. To avert such failures, it's crucial to have adequate drainage behind the retaining wall.
Absolutely! Even a 2-foot retaining wall needs an effective drainage system. Without it, water can build up behind the wall, leading to pressure that might cause the wall to lean or even collapse. All walls need systems to manage water effectively, preventing damage over time.
One major thing to avoid when building your retaining wall is lining the back of your wall with plastic sheeting as this will surely result in the pooling of water behind the wall.
Gravity retaining walls
They are the simplest and earliest recorded type of retaining wall. Built of concrete, masonry, brick, blocks or mass cast-in-situ concrete, these hard-wearing structures rely on their large weight to resist toppling and sliding caused by the lateral earth pressure from the soil behind them.
Walls made of concrete retaining wall blocks less than 3 feet tall can be built by do-it-yourselfers, but anything taller requires a professional. Considerable knowledge and experience are needed before undertaking such a project. Research local building codes, especially if erosion and runoff are concerns.
The fabric prevents these coarse-grained materials from infiltrating drainage channels, including the gravel and drainpipes. In turn, this allows water a safe, streamlined path to outlets below and away from the retaining wall.
Excavation
Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.