Types of Retaining Walls: A Student's Guide
Walk through any hillside neighborhood, highway cut or riverbank and you'll see walls quietly holding the ground in place. Some are massive blocks of stone. Others are slim concrete stems with a footing hidden underground. Some look like stacked wire baskets full of rocks. They all do the same job, but in very different ways. Understanding the types of retaining walls is one of the first steps for any student interested in civil or geotechnical engineering.
In this article, you will learn the main types of retaining walls, how each one resists the pressure of soil, where engineers tend to use them, why drainage matters for every design, and how students can see retaining walls built with communities in the field.
What a retaining wall has to resist
A retaining wall holds back soil that would otherwise slide or slump downhill. The soil pushes sideways against the wall, and water trapped behind it adds even more pressure. According to the Federal Highway Administration's Project Development and Design Manual (Chapter 10), water that isn't drained creates hydrostatic pressure, which increases the load the wall must resist. Choosing the right type depends on the height of the wall, the soil, the space available and the budget, decisions that licensed engineers make for each site.
The main types of retaining walls
Gravity walls
Gravity walls rely on their own mass, using stone, concrete or other heavy materials, to resist soil pressure. They often lean back slightly into the slope for added stability. Short gravity walls are common in landscaping, while taller ones are usually built as composite structures today.
Cantilever walls
Cantilever walls use a steel-reinforced concrete or masonry stem, often shaped like an inverted T, connected to a large footing. The footing turns the sideways push of the soil into downward pressure on the ground below. They use much less material than gravity walls.
Sheet pile walls
Sheet pile walls are made of interlocking sheets of steel, vinyl, wood or other materials driven into the ground. They are typically used in soft soils and tight spaces. Taller sheet pile walls usually need anchors.
Anchored walls
Almost any wall can be anchored. Cables or stays are fixed into the rock or soil behind the wall to add strength. Anchored walls are useful where loads are high or where a slender wall would otherwise be too weak.
Gabion walls
Gabions are wire mesh baskets filled with rock. They are free-draining, which makes them a good option where groundwater is present.
Other approaches
Engineers also use soil nailing, where steel bars are inserted into a slope, mechanically stabilized earth, which reinforces soil with layers of mats or straps, and crib walls, built from interlocking cells filled with granular material.
| Type | How it resists soil | Often used when |
|---|---|---|
| Gravity | Its own weight | Sites with room for a heavy, wide wall |
| Cantilever | Reinforced stem and footing | When saving material matters |
| Sheet pile | Interlocking sheets driven into soil | Soft soils and tight spaces |
| Anchored | Cables or stays fixed behind the wall | High loads or slender walls |
| Gabion | Heavy, free-draining rock baskets | Sites with groundwater |
Source: FHWA PDDM, Chapter 10, section 10.4.
Why drainage and supervision matter for all types of retaining walls
Drainage protects every design
No matter the type, water is a wall's biggest enemy. The FHWA manual explains that drainage systems and weep holes relieve hydrostatic pressure behind the wall, which helps keep the soil and the structure stable. Even so, no wall type is safe without a design made for its specific site by a qualified professional.
Licensed engineers make the call
Retaining walls hold back tons of soil near homes, paths and people. That's why design and construction must be led by licensed professionals. Our article on licensed structural oversight explains why this matters so much in volunteer projects.
Seeing retaining walls built in the field
In Lima's hillside settlements, many homes sit on loose soil and rock, and retaining walls help protect families and paths below. Safe Homes Movement, powered by MEDLIFE, builds retaining walls with these communities. Every project follows a 50/50 model: residents identify the need and work on site, while local engineers lead the design and supervise construction.
For students, this is a chance to see the theory in action: how engineers read the slope, plan drainage and guide the build. Here are 5 reasons civil engineering students benefit from hands-on work abroad, and how to gain engineering volunteering experience with Safe Homes.
On the development service learning trip, students join projects in Lima, Cusco and Tena. Trips run in summer, winter and spring.
Learn how walls hold up hillsides
Understanding the types of retaining walls is easier when you see one go up on a real slope, guided by engineers and built with the families it protects.
Fill out the form to get dates, eligibility details and next steps for the Development Service Learning Trip.
Frequently asked questions
What are the main types of retaining walls?
The main types include gravity, cantilever, sheet pile, anchored and gabion walls. Engineers also use soil nailing, mechanically stabilized earth and crib walls.
Which type of retaining wall is strongest?
There is no single strongest type. The right choice depends on wall height, soil, groundwater, space and budget, and it should always be decided by a licensed engineer.
Why do retaining walls need drainage?
Water trapped behind a wall creates hydrostatic pressure, which adds load. Good drainage reduces that pressure and helps keep the soil and the wall stable.