Seawall Foam Injection in South Florida: How It Works and When It Fits

It is permeation grouting with a polyurethane resin. NCFI describes the Terra-Lok line as single-component, low-viscosity, moisture-activated systems used as permeation grouts to stabilize non-cohesive soils by essentially gluing them together, and lists seawall and bulkhead repair among the applications. [ncfi.com]

The technical data sheet for Terra-Lok 24-120 calls it a low-viscosity, single-component, hydrophobic polyurethane used for increasing the load-bearing capacity of loosely bound soils and filling voids, and says it is ideal for stopping active or flowing water leaks and eliminating water seepage through cracks in stationary concrete structures. [ncfigeo.com]

In plain terms: the resin goes in as a thin liquid, finds the water moving through the fill, and turns that wet sand into a solid mass water cannot pass.

Terra-Lok 24-120 is injected through small ports and permeates the soil. When it meets the moisture in the soil, the polyurethane reacts and expands, binding the sand grains around it. [profoam.com]

Because the resin is hydrophobic, it reacts with water rather than mixing with it. NCFI lists high unconfined expansion, 100 percent solids and variable reaction times among its properties; a catalyst sets the speed, with rise times from under a minute to a few minutes, so the crew can match the foam to how fast water is moving. [ncfigeo.com]

NCFI's published results for the product cured in fine sand show a density of 55 pounds per cubic foot and a compressive strength of 2,490 psi at 10 percent deflection, with shrinkage under 4 percent. Those are laboratory figures on sand castings, not a promise for a specific wall, but they show why the cured mass behaves like a solid rather than a soft filler. [ncfigeo.com]

The result NCFI describes is a solid, water-tight barrier in the soil. Water stops moving through the joints and footer, and because water stops moving, sand stops moving with it. The hole in the yard was never the problem; the flow of water that carried the yard away was. [ncfi.com]

• Voids behind or under the wall found during inspection, with the panels and cap still sound.
• Sinkholes or settlement in the yard along the wall that keep coming back after being filled with dirt.
• Water and soil migrating through cracks, panel joints or a footer with gaps under it, especially where the leak is below the waterline and hard to reach from outside.
• Walls where digging out the yard to rebuild the backfill would mean removing a pool deck, a patio or landscaping that is otherwise fine.
• Walls where the owner wants to stay under the repair threshold that would trigger the city's current height standard; in Fort Lauderdale that is 50 percent of the wall's length or value. Sealing fill behind an existing wall is a repair, not a rebuild. [waterfronttimes.com]

Foam injection does not fix structural failure. It will not pull a leaning wall upright, replace a corroded tie-back rod, rebuild a cap that has separated from the panels, or restore a panel that has cracked through. Those walls need forms-and-rebar work, new tie-backs and anchors, or replacement, and injecting foam behind a wall that is about to move is money spent on the wrong problem.

Engineers list rotation and corrosion alongside cracking and soil loss as inspection triggers. Soil loss is what foam addresses; rotation and corrosion are what it cannot. [cumminscederberg.com]

It is not a substitute for drainage: if clogged weep holes are pushing the wall, the drainage has to be restored too. And it does not raise the wall; if the cap is being overtopped by king tides, that is a height question, covered in the seawall height rules guide.

It starts with an inspection. Langley Coastal's inspections include underwater photos and video, because the leak is usually below the waterline: an open joint, a seam below the mud line, or voids under the footer. The report shows where the water is getting through and whether the wall is sound enough to seal.

On the day of the work, the crew drills small injection ports through the cap or down through the yard along the wall, spaced to reach the voids the inspection found. The resin is pumped through the ports in sequence along the wall so each injection ties into the last.

Ports are patched when the work is done. There is no excavation and no forms to strip; the yard, deck and dock stay in place. A wall that also has cracks in the concrete usually gets hydraulic cement crack repair on the same visit. The seawall repair page lists the methods.

NCFI states that its single-component Terra-Lok systems are NSF-61 certified, making them safe for use near a potable water source, and that the cured product is inert and does not leach into the soil or groundwater. [ncfi.com]

On lifespan, the manufacturer says the cured foam is inert and built to withstand the test of time in challenging conditions. It does not publish a service life in years, and neither do we. [ncfi.com]

The honest answer is that the repair lasts as long as the wall stays sound. If the panels and cap hold, the sealed fill holds; the cured material is a solid, hydrophobic mass that does not wash out. If the wall later moves for a structural reason, new gaps can open and need attention.