During commercial property inspections, retaining walls are often found at parking lots, along property boundaries, and where changes in site elevation create access to lower levels. Some walls serve only to retain soil, while others are integrated with stairways, ramps, or tiered landscape features. They range from large structures that span long distances and support significant changes in grade to smaller site walls used around building perimeters, service areas, or walkways.

This article reviews common types of retaining walls, inspection approaches, and common deficiencies buyers, owners, and property managers should understand.

Common Types of Retaining Walls

Retaining walls are installed to manage changes in site topography and are designed to hold back soil and prevent erosion on a slope or uneven surface. The way they achieve this depends on whether gravity alone is sufficient or whether additional supporting materials are required. For this reason, inspectors typically encounter either a gravity retaining wall or a reinforced retaining wall.

Gravity Retaining Wall

Gravity retaining walls are designed to hold back soil primarily through their own weight without additional reinforcement. These are often shorter walls constructed of poured concrete, concrete blocks, rock, boulders, or gabion systems. Most gravity walls are built with a slight backward slope, leaning toward the soil they are retaining. These walls typically do not include visible reinforcement. Although a concrete retaining wall may be reinforced internally with steel, it is not considered a reinforced retaining wall system unless it uses structural elements that extend and anchor into the surrounding soil.

Reinforced Retaining Wall

Reinforced retaining walls are often associated with taller walls or walls that must hold back larger volumes of soil or additional loads. These walls include some form of structural attachment to the soil to improve stability and resist movement, such as tiebacks, deadmen, or piles. Common construction materials include timber and poured concrete.

Wooden or timber retaining walls may make it easiest to determine whether reinforcement is present. Seeing a shift from the horizontal grain to an exposed end grain can indicate that a deadman or tie-back is present. Concrete retaining walls are more difficult to classify visually, as deadmen or tiebacks are often buried perpendicularly behind the wall, extending into the retained soil.

Inspection Approaches

The baseline scope of the International Standards of Practice for Inspecting Commercial Properties (ComSOP) is to inspect retaining walls when they are likely to adversely affect the structure. Two useful approaches are assessing stability through a plumb, level, square, and straight lens, and combining macro and micro viewpoints.

Structural Stability

Plumb, level, square, and straight (PLSS) is an inspection approach for visually assessing structural stability.

Plumb: Looking for vertical alignment along the full height of the wall.
Level: Looking at horizontal components for unevenness or deflection.
Square: Looking for walls that are slanted inward or outward.
Straight: Looking down the length of a wall to identify bows, waves, or irregularities.

Macro and Micro Viewpoints

Micro viewpoint: Assessing the structure from close proximity.
Macro viewpoint: Assessing the structure from a distance for a wide view.

Using both approaches can change how a condition is interpreted. A detail that looks like a defect up close may look less severeâ€”or more concerningâ€”when viewed in the broader context of the wall and surrounding site.

Common Deficiencies

Retaining walls can experience a variety of issues that may develop over time. The following conditions may indicate underlying problems that can compromise structural stability if left unaddressed.

Settling

A stable retaining wall relies on properly supported soil behind it. When the backfill settles or shifts, the surface above may dip or slump, placing added stress on the wall. Uneven grades, depressions, or separation near the top of the wall may indicate settlement or loss of support. These conditions should be noted, as ongoing movement can affect the wallâ€™s stability over time.

Improper Drainage

The drainage system is typically made up of openings placed along the base or slightly above the base that allow trapped moisture to escape from behind the wall. Some walls may have French drains or other accepted methods of de-watering installed behind the wall.

Water trapped behind the wall can build pressure. Clogged openings, blocked pipes, or compacted backfill can prevent water from escaping, saturating the soil and leading to material deterioration. Standing water, erosion, or signs of moisture should be noted, as these may indicate inadequate drainage.

Cracking

Cracks may be present from settlement, soil movement, or other forms of stress. Common types include:

Vertical crack: Runs up and down the wall. Evaluate for signs of movement, such as widening at the top or bottom. Concrete commonly develops vertical cracks, and a crack without evidence of movement may be less concerning but should still be documented.
Horizontal crack: Runs across the wall and should be evaluated carefully for movement and stress.
Stair-step crack: A stepped crack pattern commonly seen in masonry or block walls. This type of cracking may indicate movement or stress within the wall and should be evaluated with other observed conditions.

Wide and extensive cracks should be documented. Other potential issues include leaning or bulging walls, separation of segments, material deterioration, and clogged drainage.

A retaining wall that appears out of plumb, combined with settlement in the soil behind it, may indicate deficiencies related to wall design or backfill support and could adversely affect the structure. When observed, such conditions should be documented and may warrant further evaluation by a qualified professional.

Source: Certified Commercial Property Inspectors Association (CCPIA). PHW Inspections is a CCPIA member. Original article: https://ccpia.org/inspecting-retaining-walls-at-commercial-properties/

Inspecting Retaining Walls at Commercial Properties