Retaining walls look simple. Stack some brick or stone and the hill stays put.

That’s not how it works. Walls built without proper planning fail. Some lean. Some crack. Some collapse outright, taking soil and landscaping with them. A masonry professional can spot drainage and soil issues before they become expensive problems.

The fix after the fact always costs more than doing it right the first time.

Before this project starts, here’s what you need to know.

What a Retaining Wall Actually Does

A retaining wall holds back soil. That sounds straightforward, but the forces involved are serious.

The soil is heavy. Wet soil is heavier. When rain soaks into the ground behind a wall, the pressure on that wall multiplies. The wall has to resist that pressure constantly, not just on dry days.

Water management is part of the job too. Trapped water behind a wall is one of the most common causes of failure. A wall built without proper drainage doesn’t just struggle over time. It loses.

When You Need a Permit

Most local governments require a building permit for retaining walls over a certain height. In many areas, that threshold is three to four feet.

The International Residential Code (IRC) generally requires engineered drawings for walls over four feet, measured from the bottom of the footing to the top of the wall. That means a licensed structural professional needs to sign off before any ground gets broken.

Don’t assume a shorter wall skips the permit process. Check with your local building department first. Getting caught without a required permit means stopping work, applying retroactively and possibly tearing down what’s already built.

The Drainage Problem Most Homeowners Ignore

Poor drainage is the number one cause of retaining wall failure. Full stop.

When water can’t escape, it builds up behind the wall. That pressure pushes outward. Even a well-built wall struggles against constant water pressure over time.

Every retaining wall needs a drainage plan. That includes:

• Gravel backfill directly behind the wall to let water move through
• A perforated drain pipe at the base of the wall to carry water away
• Weep holes at regular intervals in the wall face to release pressure
• Proper grading behind the wall to direct surface runoff away from the base

Skipping any one of these puts the wall at risk. A mason who doesn’t bring up drainage during planning is a red flag.

Footing and Foundation Requirements

A retaining wall needs a concrete footing buried below the frost line. This base anchors the wall and spreads the load into stable soil.

Footing depth depends on local frost depth, soil type and wall height. In climates where the ground freezes in winter, a footing that doesn’t go deep enough will heave and shift with the freeze-thaw cycle. That movement cracks mortar joints and destabilizes the whole structure.

For mortared brick or stone walls, the footing is not optional. Dry-stacked walls have more flexibility, but taller dry-stacked walls still need a stable, compacted base to hold up over time.

Brick vs. Stone for Retaining Walls

Both materials work, but they perform differently depending on the wall’s height and setting.

Brick

Brick retaining walls work best for lower applications, typically under four feet. They suit formal garden settings, walkway borders and low landscape edges.

Brick walls require mortar for structural use. The consistent size makes them easier to lay in level courses, but mortar is less forgiving of soil movement than stone. If the footing shifts, the joints crack.

Brick also absorbs more moisture than dense stone. In areas with heavy rainfall or freeze-thaw cycles, this speeds up deterioration if the wall isn’t properly sealed and maintained.

Stone

Natural stone is a stronger choice for taller retaining walls, especially when dry-stacked. The irregular shapes interlock and the weight of the stone adds stability.

Dry-stacked stone walls flex slightly with soil movement without cracking. They also drain naturally through the gaps between stones, which reduces water pressure behind the wall.

Mortared stone walls give a cleaner finished look but require the same footing and drainage considerations as brick.

For walls over four feet or on steep ground, natural stone handled by an experienced mason is the more reliable choice.

Height Limits and What They Mean

Wall height affects everything: permit requirements, engineering needs, footing depth and material selection.

Walls under two feet are the most straightforward to build. Walls between two and four feet need proper footings and drainage. Walls over four feet almost always require a structural engineer’s input and a building permit.

Walls over six feet are serious structural projects. They require engineered designs, deep footings and in many cases reinforcement within the wall itself. That’s not a DIY project, regardless of how skilled the homeowner is.

Warning Signs a Retaining Wall Is Failing

Failures rarely happen without warning. Watch for these signs:

• Leaning or bowing in the wall face
• Horizontal cracks running across multiple courses
• Bulging at the base or middle of the wall
• Soil washing out from behind the wall after rain
• White mineral deposits on the face, which indicate water moving through the wall

A wall showing any of these signs needs professional assessment. Waiting makes the repair more expensive. In some cases a failing wall can be reinforced. In others it has to come down and get rebuilt from scratch.

Frequently Asked Questions

Do I need an engineer for a retaining wall?

For walls under four feet, an engineer is often not required, but local rules vary. For walls over four feet measured from the bottom of the footing, most jurisdictions require engineered drawings before issuing a permit. Confirm with your local building department before starting. The cost of an engineering review is far less than a wall that fails inspection or comes down.

Can I build a brick or stone retaining wall myself?

Low dry-stacked stone walls under two feet can be a manageable DIY project with the right preparation. Mortared brick or stone walls require masonry skills, footing work and drainage installation. Walls over three feet should be handled by a professional mason. The structural and drainage requirements at that height go beyond what most homeowners can safely manage on their own.

How long does a properly built retaining wall last?

A well-built masonry retaining wall with proper drainage and footings can last 50 years or more. Walls that fail early almost always have drainage problems, shallow footings or both. Material quality matters, but proper construction technique matters more.

What is the best material for a retaining wall in wet or rainy conditions?

Natural stone, especially dry-stacked, handles wet conditions well because water drains naturally through the wall. Mortared walls of any material need weep holes and gravel backfill to manage water. In very wet conditions, a perforated drain pipe at the base is standard practice regardless of which material is used.

How much does a brick or stone retaining wall cost?

Costs vary by wall height, length, site conditions and material. Brick retaining walls typically run $25 to $50 per square face foot installed. Natural stone walls range from $25 to $75 or more per square face foot. Taller walls with engineering requirements and drainage systems cost more. Get at least two written quotes from licensed masons before committing to any contractor.