Do You Need Drainage Behind a Retaining Wall
Do You Need Drainage Behind a Retaining Wall

Experts have found that retaining wall drainage systems are essential to prevent any failures. About 80% of the failures that occur are due to improper retaining wall drainage. Therefore, despite how useful and attractive retaining walls are in many yards, they can fail if proper drainage wasn’t considered. So, do you need drainage behind a retaining wall? Absolutely! Whether you have somebody else design your wall or you plan to do it on your own, make sure to understand how drainage from a retaining wall works to obtain the best results.

Why Do You Need Drainage in the First Place?

A retaining wall’s mission is to hold back soil and help prevent leaning, caving, or buckling. However, if you happen to have too much water behind the wall, this will cause the wall to lean, cave in, or buckle from all of the pressure. When this happens, it will develop in the weakest spot of the retaining wall. Make sure to remember its importance while planning your outdoor living.

Retaining Wall Drainage
Retaining Wall Drainage

Proper Drain for Retaining Wall

In order to drain properly, most retaining walls need soil compaction, weep holes, gravel backfill, and pipe or toe drains. Continue reading to learn about these four important features.

Soil Compaction

Not only does soil compaction create strength, but it also reduces the dirt’s permeability, restraining water from seeping into the space behind the wall. To compact the soil properly, it’s essential to use a plate compactor or any other similar tool.

Weep Holes

These openings at the front of the wall are necessary to let moisture escape. Depending on the drainage need, they can be either at the base of the wall or in a grid pattern all across the whole wall. Furthermore, moisture protection substances as varnishes or waterproof overlays are needed to protect the retaining wall, as the water flow could create stains if the material isn’t properly protected.

Gravel Backfill

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. With this backfill, water will be able to flow down the wall to the weep holes or drains when it gets into space, instead of becoming bogged down in the soil. Also, it’s possible to fill the top six inches of space with native soil, which allows you to design a garden and use the area for planting.

Toe Drains

A retaining wall drainage pipe or toe drain is a pipe with perforations that collects water all along the wall and then drains it to the exterior; either to the sides or through the front of the wall. While tall walls need multiple pipe drains at different heights, most pipe drains are located at the base of the wall, vented every 30 to 50 feet. Rodent mesh is commonly needed to prevent debris from getting into the pipes and clogging them.

Drainage From Retaining Wall
Drainage From Retaining Wall

Other Factors to Consider

It’s important to avoid the excess of humidity during the construction of the retaining wall, which is why it shouldn’t be installed when it’s likely to rain. Also, it’s sometimes required to divert drainage along the slope above the wall while construction is on.