Crack Reopens Only After Wet Season Following Injection Decision Tree

Why this matters

An injected crack that stays tight through the dry months and reopens every wet season is not an injection failure in the chemistry sense. The resin bonded; the structure moved. Reopening tied to seasonal moisture tells you a live structural or geotechnical driver is still working the wall, and the injection was treated as a final repair when it should have been a seal applied after the movement was arrested. This tree separates a true bond failure from active movement, because re-injecting an actively moving crack just buys one more dry season before the next callback.

Symptom presentation

The crack reopens during or just after the rainy/wet period, often at the same width it was before injection, and may close partially when the soil dries. You may see a hairline re-separation directly through the cured resin bead, fresh efflorescence or active seepage at the crack, or the resin intact but the concrete cracked alongside it. Reopening is frequently seasonal-cyclic: tighter in late summer, wider in late winter/spring depending on climate.

Quick checks

• Read the crack monitor or caliper across the crack now and compare to the post-injection baseline. Log width and any vertical offset.
• Note the season and recent precipitation. Check whether soil at the wall is saturated (probe), and whether gutters, downspout extensions, and grade slope are functioning.
• Inspect the resin bead: is the failure THROUGH cured resin (bond/movement) or in adjacent concrete (the wall flexed beside a rigid epoxy)?
• Was the original injection epoxy (rigid, structural) or polyurethane (flexible, water-cutoff)? Rigid epoxy in a moving crack will telegraph movement to the adjacent concrete.

Isolation tree

1. Is there measurable cyclic width change between wet and dry readings (the crack breathes)?

   • If yes, the crack is ACTIVE. Branch to step 2.
   • If the crack reopened once and is now stable, it was a one-time event (settlement or a single bond defect); re-evaluate as a static repair, not seasonal.

2. Is the movement primarily horizontal width change at a vertical/diagonal crack, with the wall otherwise plumb?

   • Likely expansive-clay shrink/swell lateral pressure cycling against the wall. Confirm with soil PI.

3. Is there vertical offset (one side higher than the other) that grows in the wet season?

   • Differential SETTLEMENT/HEAVE driven by seasonal moisture under the footing. Shoot an elevation survey wet vs dry.

4. Is the failure mode rigid epoxy in adjacent concrete with no soil moisture correlation?

   • The epoxy was too rigid for a working joint; the wall needed a flexible polyurethane or a control-joint approach, not a structural weld.

5. Is active water entering through the reopened crack with no width change?

   • Hydrostatic water path reopened a polyurethane seal; the seal shrank or the crack micro-moved. A water-cutoff re-injection plus drainage is the path.

Confirming diagnosis

• ACTIVE expansive movement: Install a crack monitor and read it across a full wet/dry cycle, or accelerate by soaking/drying the adjacent soil and watching the gauge. Soil plasticity index over 25 (Atterberg, ASTM D4318) confirms expansive potential.
• Differential heave/settlement: Two elevation surveys (manometer or laser), one in the wet season and one in the dry, that show the footing rising or dropping seasonally confirm a geotechnical driver under the foundation.
• Rigid-vs-flexible mismatch: Cored sample or visual confirms the crack reopened beside an intact epoxy bead, proving the wall flexed and the rigid resin transferred stress.

Remediation

• Arrest the driver first. For expansive clay, stabilize moisture: gutters and 6 ft downspout extensions, regrade to 6 in fall over 10 ft per IRC R401.3, root/moisture barriers, and address irrigation. Then re-seal.
• For differential seasonal movement at the footing, the crack is a symptom; underpin (helical or push piers) or stabilize the soil before any final injection. Injection alone will not hold.
• For a working joint, switch chemistry: flexible polyurethane that accommodates cyclic width, or convert to a routed-and-sealed control joint that is allowed to move.
• For water-only reopening, re-inject with hydrophilic/hydrophobic polyurethane and add an interior drain or exterior drainage to relieve hydrostatic head.
• Only re-inject with structural epoxy after movement is demonstrably arrested over at least one full season on the monitor.

Field notes

• The chemistry choice is the most common silent error here. Structural epoxy welds a crack rigid; if the wall keeps working, the epoxy does not fail but the concrete cracks beside the bead, and to the eye the "injection failed." It did not; it was the wrong material for a moving joint. When in doubt about future movement, flexible polyurethane tolerates cyclic width that epoxy will not.
• Seasonal direction is a strong diagnostic. Note whether the crack is wider in the wet season or the dry season. Expansive clay swells when wet and pushes the wall, so a crack driven by lateral clay pressure tends to widen in the wet season. A crack driven by drought-shrinkage settlement under a corner tends to open in the dry season. The timing points to the mechanism.
• Read the monitor at the seasonal extremes, not on a fixed calendar. The whole point is to capture the wet peak and the dry trough; a read taken mid-cycle understates the true range of movement and can make an active crack look dormant.
• Efflorescence and active seepage at the reopened crack tell you water is moving through it now, which steers you toward a water-cutoff polyurethane plus drainage rather than a structural epoxy weld.
• Do not re-inject with structural epoxy until the monitor is flat across a full wet/dry cycle. Sealing an actively moving crack just buys one dry season before the next callback.

References

• ASTM D4318, Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils.
• ACI 224.1R, Causes, Evaluation, and Repair of Cracks in Concrete Structures.
• IRC R401.3, surface drainage / grading away from foundation.
• ICRI Technical Guideline 210.1, Visual Inspection of Concrete (crack classification, active vs dormant).
• FEMA P-2090 guidance on expansive-soil foundation movement.