Proper drainage is critical to prevent water buildup behind the wall, which can lead to pressure and eventually cause the wall to fail. For effective drainage, the choice of gravel is paramount. Fractured rock is often the preferred choice for the drainage layer of retaining walls.
Crushed stone is the preferred material for use behind retaining walls. Check them out at http://www.grgravel.com/ Try to install a minimum of twelve inches of crushed stone behind your wall. It is best to place the stone as you go to ensure proper compaction on filling.
Gravel is a good filling materials and it will cover the voids in gaps and get consolidated well.
3/4'' clear gravel is typically used for drainage BEHIND the wall. It's excellent for this purpose.
Proper drainage is critical to prevent water buildup behind the wall, which can lead to pressure and eventually cause the wall to fail. For effective drainage, the choice of gravel is paramount. Fractured rock is often the preferred choice for the drainage layer of retaining walls.
We recommend a 10-20mm clean, free drainage aggregate such as river stones or coarse crushed rock. It is imperative that the material is free from any soil, sand or other fines to ensure that water can flow freely through the drainage area and away from the back of the 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.
Poured concrete is the cheapest type of retaining wall, in terms of materials. Pressure-treated pine is next, and wood retaining walls are becoming more popular now. If you prefer stone, granite is generally the least expensive option.
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.
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.
Filled Wall Blocks Promote More Efficient Drainage
Rainwater, snow, and ice can all accumulate inside precast retaining walls composed of hollow blocks.
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.
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.
A retaining wall should have AT LEAST 12" (30 cm) of gravel (or other similar material; see text for more info) behind its entire length and height. Should be equal to or slightly larger than wall length.
After each row is completed, you should use backfill to reinforce the retaining wall. Use crushed gravel to fill in the back and sides of your blocks. Backfill helps with water drainage.
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.
In order to provide proper drainage, at least 12 inches of granular backfill (gravel or a similar aggregate) should be installed directly behind the wall. Compacted native soil can be used to backfill the rest of the space behind the wall.
Add an angular aggregate — clean, crushed stone or gravel between 1/2- and 3/4-in. — as a base under the retaining wall and as back fill behind it.
The trench should be deep enough to bury at least half the height of your first course of blocks plus 3 inches of paver base. Depending on the size of your blocks, this depth could be 4 to 8 inches. The trench should be twice as wide as a single block.
You may be wondering what the situation is when a retaining wall might be necessary – let's take a look! In most cases, a retaining wall is needed when the slope of the land exceeds a certain angle, usually around 4:1.
Any reinforced wall or walls over 4 ft. (1.2 m) in height or with slopes or other surcharges above the wall will need a toe drain. In all cases wall rock is located within the cores of the block and a minimum of 12 in. (300 mm) behind the block.
Best Backfill Material for Retaining Wall
To reduce the pressure, a 3/4″ angular crushed clear stone (ASTM #57) is used to backfill a retaining wall. Clear stone is an important aspect of this aggregate. Clear stone refers to the stone being washed and clear of fines.
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.