The Problem
The backyard retaining wall on this Wagner Farm area property had been moving for several years. When we inspected, a 12-foot section of the wall had developed a forward lean of approximately 2 inches at the top, two courses of brick near the center had displaced forward and separated from the courses above, and the cap units on that section had rotated and cracked. The seven-step garden stair that ran perpendicular to the wall had open mortar joints on every tread nosing and two step cap units that had cracked through.
The cause was drainage failure. The wall had no weep holes in the lower courses - none were specified when it was built in 1985, which was common practice. Hydrostatic pressure from groundwater and surface runoff had accumulated against the back face of the wall with no outlet. That pressure had pushed the center section forward progressively. The drainage problem had to be solved before any masonry repair would hold.
Our Solution
We addressed drainage first. We excavated behind the wall’s displaced center section, installed a 4-inch perforated drain tile in a gravel bed at footing level, and brought the drain tile to daylight at the garden bed edge. We also drilled 1-inch weep holes through the mortar joints at the base course on 32-inch centers along the full wall length to give future groundwater a path out.
With drainage corrected, we rebuilt the displaced section. The two separated courses were dismantled, the footing was inspected and found sound, and we relaid those courses plumb with Type S structural mortar - the correct specification for a load-bearing retaining wall in ground contact. The displaced cap units were reset and fully bedded. We used a 4-foot level and a plumb bob string line to bring the rebuilt section back to alignment with the undisturbed sections on each side.
The full wall was then repointed in Type S mortar at 3/4-inch depth. The seven garden steps had their tread nosing joints ground out and repacked, and the two cracked cap units were replaced with matching brick set in full Type S mortar beds with a positive forward slope to shed water off the tread.
The Result
The retaining wall is plumb and fully repointed. Drainage is now functional - we observed water running from the new weep holes during a watering test before we left the site. The garden steps have sealed nosing joints and correct tread slope. The homeowner has a structurally stable wall rather than a wall that was one heavy rain away from a larger displacement event.
Frequently Asked Questions
Why do brick retaining walls fail without weep holes? A brick retaining wall holds back soil and everything that drains through it - groundwater, irrigation, and storm runoff. Without weep holes, that water has nowhere to go and builds hydrostatic pressure against the back face of the wall. Brick and mortar are strong in compression but relatively weak in tension. Sustained hydrostatic pressure eventually overcomes the wall’s lateral capacity and pushes it forward. Weep holes at the base course let water out before pressure builds.
Can a retaining wall that has leaned forward be pushed back into position? Not reliably. Once a masonry wall has displaced and the mortar joints have cracked and opened, the internal bond is broken. Pushing it back compresses the cracked joints but does not restore bond strength. The correct approach for a displaced section is to dismantle those courses, correct the underlying cause, and relay from a sound footing. Trying to push and pin a leaning masonry wall is a short-term fix.
Why Type S mortar for the retaining wall but not for above-grade repointing work? Type S has higher compressive and bond strength than Type N and better resistance to moisture in ground contact. A retaining wall is a structural element in contact with soil and groundwater. It needs mortar rated for that environment. Above-grade repointing on older residential brick uses Type N or Type O because the lower strength mortar stays softer than the brick and allows freeze-thaw movement to be absorbed in the joint rather than in the brick face. The application drives the specification.
