Most retaining wall failures are not masonry failures. Retaining wall repair that succeeds long-term starts with that premise. The brick or stone deteriorates, yes. Mortar joints erode and coping caps crack. But the force that pushes the wall outward, opens the joints, and eventually shifts brick courses out of their original plane is almost always water - specifically, water that accumulated behind the wall because the drainage system was inadequate, blocked, or absent.
This distinction matters because it determines what actually fixes the problem. Repointing mortar joints on a retaining wall that is still under hydrostatic pressure will not stop the movement. The wall will continue to lean. The new mortar will crack and open just as the old mortar did. The repair that lasts is the one that solves the drainage problem first.
Since 1987, we have rebuilt and repaired brick and stone retaining walls on properties across Chicagoland’s North Shore, Lake County, and northwest suburbs. This post covers why walls fail, what repair versus rebuild looks like, and the role drainage plays in every retaining wall project we do.
Why Retaining Wall Repair Starts Behind the Wall
A retaining wall is a gravity structure. It holds back soil by weight and by the structural integrity of the masonry system. That system manages specific loads: the weight of the soil and whatever sits on top of it, and any surcharge loads from structures or vehicles above the retained grade. TMS 402 - the reference standard for structural masonry design adopted by the International Building Code - defines the design requirements that govern both construction and repair of load-bearing masonry walls.
What the system is not designed to handle is prolonged hydrostatic pressure. Dry soil has a predictable weight per cubic foot. Saturated soil is heavier, and moving water exerts pressure on any surface it presses against. If a retaining wall is built without adequate drainage, or if the original drainage system deteriorates, the pressure loading behind the wall increases every time it rains and every time snow melts.
In Chicagoland, the freeze-thaw dimension compounds this. Water that has accumulated behind the wall does not just create hydrostatic pressure - it freezes. Frozen saturated soil expands, and that expansion pushes against the wall from behind with force that exceeds what the mortar joints and the footing system were designed to carry. The Great Lakes Integrated Sciences and Assessments program at the University of Michigan documents the Chicago region as experiencing dozens of freeze-thaw cycles each winter. Each cycle, if water is present behind the wall, applies and releases a heave force on the back face.
The result is progressive movement. The wall leans slightly after year one. After five winters, the lean is visible. After a decade, brick courses have shifted and horizontal cracks have opened. By the time most property owners recognize the problem, the wall has been under sustained pressure long enough that drainage correction alone is not sufficient. Rebuild is the only path.
The weep holes in a retaining wall’s lower courses are the pressure relief valve. For more on how weep holes work in masonry systems and why they matter, see weep holes in brick walls and drainage.
Retaining Wall Repair on Highland Park and Lake Forest Properties
Highland Park and Lake Forest are where we see the most retaining wall work on the North Shore. Both communities have significant topographic relief - homes sit above and below grade changes that would not exist in the flat suburban geography further west.
In Highland Park, the ravine corridor creates properties where grade changes of eight to fifteen feet are common. The city’s documented masonry challenges include chimney settlement on homes near ravine edges, where soil behavior differs from standard suburban lots. That same soil instability affects retaining structures: ravine-adjacent walls manage the grade differential between two levels of the property, sometimes with a structure or a driveway on the upper level adding surcharge load. The drainage situation behind these walls is complicated by the ravine’s own moisture dynamics - persistent groundwater, high humidity, and water flow during rain events that concentrates at the base of grade changes.
Homes near Highland Park’s ravines also show differential movement from soil behavior near ravine edges. A retaining wall that is cracking in a stair-step pattern on a ravine-adjacent lot may be responding to both hydrostatic pressure and soil movement. The root cause assessment requires looking at both conditions before specifying a repair.
Highland Park’s median home age is 1958, and the housing stock ranges from 1920s estates near the lake to 1990s colonials further inland. The variation matters for material specification: an original limestone retaining wall from the 1920s and a concrete block wall from 1975 require fundamentally different repair approaches. We do not apply the same mortar or the same drainage solution to both.
In Lake Forest, many properties have estate-scale landscapes with formal retaining walls built as part of the original site design. Lake Forest’s median home age is 1964, but its historic estates predate that median significantly. When these walls need repair, material matching is important. A Lake Forest property with an original limestone retaining wall from the 1920s cannot be rebuilt in standard CMU block without affecting the character of the landscape. We source matching stone and use mortar specifications appropriate to the original material: NHL hydraulic lime or a lime-rich Type N rather than Portland cement-heavy mixes that can stain limestone and create incompatibility failures. Per NPS Preservation Brief 2, pre-1920 masonry should be repaired with lime mortar, and that principle applies to retaining walls on historic properties just as it does to building facades. Lake Forest’s Historic Preservation Commission reviews work on designated properties, and appropriate mortar specification is part of that review.
The Deerfield Project: A Documented Retaining Wall Rebuild
Deerfield illustrates the scope of a full retaining wall rebuild. The city’s housing stock is predominantly from the 1960s through 1980s suburban expansion era, and Deerfield’s documented masonry challenges include builder-grade mortar reaching end of service life. Retaining walls built in the 1970s on bi-level and split-level homes in Deerfield typically used concrete block with standard mortar application and, in many cases, inadequate drainage aggregate behind the wall.
Deerfield has a median home age of 1970. The bi-level configuration places the retaining wall at the grade transition between the lower entry level and the upper main level, and the wall often runs along the driveway or garage approach. Over 40 to 50 years, the combination of inadequate original drainage, freeze-thaw cycling, and soil movement from Deerfield’s clay-heavy ground pushes these walls toward failure.
A documented project involved a 1975 bi-level with a 60 linear-foot, four-foot-high retaining wall. The rebuild involved complete deconstruction of the existing failed wall, excavation behind the wall to expose the footing and the back face, installation of a drainage system with clean stone aggregate and filter fabric to prevent soil migration, construction of a new footing where the original had heaved, and rebuilding the four-foot wall height in new CMU block with Type S mortar at minimum compressive strength of 1,800 PSI per ASTM C270. Weep holes were installed at the base of the wall every 32 to 48 inches to provide ongoing pressure relief.
The drainage installation is as important as the masonry itself. A wall rebuilt without addressing the drainage behind it will fail again, on a timeline determined by how quickly the drainage deficiency reasserts itself.
Deerfield’s other documented primary problem is steel lintel rust causing brick displacement on its 1960s-1970s colonials - which means homeowners in Deerfield often face both lintel work and retaining wall work in the same inspection cycle. Scheduling a combined assessment is the efficient approach. See steel lintel repair for how those two problems intersect.
Repair Versus Rebuild: Making the Distinction
The decision between retaining wall repair and rebuild is about structural integrity and the status of the drainage system, not cosmetics.
Repair is appropriate when:
The wall is plumb or close to plumb, with no visible lean greater than one inch per foot of height. Mortar joints are eroded but brick courses have not shifted from their original plane. Weep holes exist and can be cleared or supplemented without major excavation. The footing has not heaved or settled significantly. Drainage improvement can be achieved without full excavation behind the wall.
At this stage, targeted mortar restoration using masonry repair techniques, weep hole maintenance or addition, and localized drainage improvement can extend the wall’s service life by 20 to 30 years. Pricing for repair work runs $500 to $2,000 in the Chicagoland market depending on linear footage and drainage scope.
Rebuild is necessary when:
The wall is visibly out of plumb with measurable lean. Brick or block courses have shifted from their original plane and the wall face is no longer flat. Horizontal cracks have opened through the full wall depth. The footing has heaved, settled, or cracked in ways that compromise the base of the wall. The drainage behind the wall has failed completely and cannot be corrected without full excavation.
At rebuild stage, the wall is deconstructed to the footing, the footing is assessed and replaced or repaired, drainage is installed to specification, and the wall is rebuilt with correct mortar type and weep hole placement. For Lake Forest and Kenilworth properties with original stone walls, this rebuild falls under stone masonry scope. Rebuilds in the Chicagoland market run $5,000 to $15,000 depending on wall length, height, and material.
Reading Cracks in a Retaining Wall
Crack patterns in retaining walls tell different stories. Understanding what a crack indicates helps distinguish drainage failure from settlement from frost heave.
Horizontal cracks running parallel to the courses on the outward wall face are the most serious pattern. They indicate that the wall is bending outward under lateral pressure - hydrostatic pressure or frost heave behind the wall is exceeding the wall’s structural capacity. A horizontal crack is not a cosmetic issue. It is a structural warning.
Stair-step cracks following mortar joints diagonally are more common in corners and at transitions. On retaining walls, stair-step patterns often indicate differential settlement in the footing below, or differential soil pressure at a point where drainage behind the wall has failed unevenly. For a fuller explanation of what different crack types indicate, see how to read cracks in a brick wall and stair-step cracks in brick walls.
Vertical cracks at corners or at the wall end are often the result of differential thermal expansion or differential settlement between two sections of wall with different drainage conditions behind them. Isolated vertical cracks may be repairable without full rebuild.
Bulging or bowing without obvious cracking usually indicates that brick or block courses in the middle of the wall have shifted outward while the courses above and below remain in their original position. This pattern typically means mortar joints at the bulge location have fully failed and the section is acting as a free body under soil pressure. Section rebuilding of the affected area, combined with drainage correction, is the appropriate response.
Mortar Specification for Retaining Wall Work
Retaining walls are one of the few applications where Type S mortar is the correct choice for standard residential work. The minimum compressive strength of 1,800 PSI per ASTM C270 provides the structural capacity needed for a wall managing lateral soil loads. Type N at 750 PSI minimum is appropriate for above-grade walls with no significant lateral load. It is not appropriate for retaining wall applications.
For walls holding back heavy soil loads or walls with significant surcharge above, Type M mortar at minimum compressive strength of 2,500 PSI may be specified. This applies in commercial applications or on walls carrying heavy live loads. Standard residential retaining walls do not typically require Type M.
One critical exception applies: retaining walls built in historic lime mortar as part of a landscape that predates 1920 - particularly on North Shore properties in Lake Forest, Kenilworth, or Winnetka where original estate walls were built in natural limestone with lime mortar - should not be rebuilt or repointed with Portland cement-based mortars. Per NPS Preservation Brief 2, pre-1920 masonry should be repaired with lime mortar or lime-rich Type O. The wall was designed around lime mortar, and that system is what should be maintained. BIA Technical Note 7B covers joint preparation and workmanship standards that apply to the repointing of both historic and modern retaining walls.
The Role of Weep Holes in Long-Term Wall Performance
A retaining wall without weep holes is a reservoir. Water accumulates behind the wall until it finds another path: over the top, through failed joints, or by pushing the wall outward. In the Chicago region where winter freeze-thaw cycling adds a heave mechanism to the hydrostatic pressure, a wall without pressure relief deteriorates faster than almost any other masonry structure.
Weep holes should be placed at the base of the wall, typically in the first or second course above grade, at intervals of 32 to 48 inches. They should pass through the full wall thickness to the drainage aggregate behind the wall. They should be sized to drain freely without allowing soil migration through the opening, which is why filter fabric behind the drainage stone matters.
On walls that were built without weep holes, they can often be cored through the wall at appropriate locations without dismantling the masonry. This is one of the least disruptive interventions available on a retaining wall showing early signs of hydrostatic pressure buildup.
Blocked weep holes are almost as problematic as no weep holes. We clear blocked weep holes as part of every retaining wall assessment and recommend cleaning them annually as part of routine property maintenance.
Understanding the Structural Context
Retaining wall failures connect to the broader category of structural masonry problems. Why Bricks Crack: Common Causes covers the freeze-thaw and lateral-load mechanisms that drive retaining wall deterioration alongside other masonry failures. How to Read Cracks in a Brick Wall gives you the vocabulary to distinguish what type of stress is producing each crack pattern. For the winter seasonal dimension, see What Winter Does to Chicago Masonry for the full picture of how freeze-thaw cycling affects masonry structures across the region. And if your retaining wall shares a drainage path with a stepped masonry structure at grade, step and stoop masonry repair covers that adjacent scope.
Scheduling Retaining Wall Assessments
Retaining wall repair is best assessed in late spring or early fall when soil moisture conditions reflect the seasonal average and any frost heave from the previous winter is fully visible. Fall inspection before winter is particularly valuable: identifying a wall that is nearing rebuild threshold before it goes through another season of freeze-thaw cycling can preserve the option for repair rather than full replacement.
We serve retaining wall projects throughout the North Shore and northwest suburbs, including Highland Park, Lake Forest, Deerfield, Northbrook, and communities across Lake County.
Call (847) 713-1648 or contact us online to schedule a free retaining wall assessment. We evaluate drainage, mortar condition, structural integrity, and footing status before recommending any repair scope. Delta - Masonry and Tuckpointing, serving Chicagoland since 1987.
Repointing a retaining wall that is still under hydrostatic pressure is not a repair. It is a delay. The wall will move again.