Poured Concrete Maintenance: Sealing, Patching, Drains

Poured concrete maintenance is the annual routine that keeps water out of a wall: inspecting the face, sealing small cracks before they widen, patching spalls before the rebar corrodes, and confirming the drain still discharges. It is cheap against the alternative. Sealer costs $0.50 to $1.50 per square foot, and a replacement wall costs $25 to $60.

What Maintenance Can and Cannot Do

Concrete is strong in compression and weak in tension, which is why it is reinforced. Maintenance protects the two things that make the wall work: the steel, and the soil beneath the footing. Keeping water away from the steel prevents corrosion; keeping water out of the backfill keeps the load where it was designed.

Maintenance cannot restore capacity that has already been lost. A wall with a horizontal crack, a lean, or widespread honeycombing has a structural problem, and sealing the surface does not address it. Those belong to an engineer, not to a tube of sealant.

The Annual Inspection

Walk the wall once a year, in spring, when freeze-thaw damage is visible and the ground is still wet enough to show drainage problems. Take photographs with a ruler against anything you find, and write the date on them.

Check the face for new cracks, rust staining, spalling, and white bloom. Check the top for a cap or grade that has settled. Check the toe for wet soil, which means water is coming through or around the wall rather than out the drain.

Compare against last year’s photographs. A 1/16-inch crack that has not changed is a maintenance item. The same crack at 1/8 inch is a trend, and trends are what matter.

Crack Repair by Type

The distinction that matters is movement. Epoxy is rigid and strong, so it is right for a crack that has finished moving and needs its tensile capacity restored. Polyurethane stays flexible and foams on contact with water, so it is right for a crack that leaks or may still move.

Routing a hairline crack into a small V before sealing gives the sealant somewhere to sit. Smearing sealant over the surface of a hairline crack leaves it sitting proud of the face, where traffic and weather peel it off within a season.

Patching Spalls

A spall is a shallow or deep breakout, and the repair depends on whether rebar is exposed. If it is, the bar has to be cleaned to bare metal, inspected for section loss, and treated with a corrosion inhibitor before any patch goes on.

Cut the edges of the patch square and to sound concrete, not feathered. A feathered edge is too thin to bond and will lift. Wet the substrate, apply a bonding agent if the product calls for it, and place a repair mortar matched to the wall’s strength.

Deep patches may need formwork to hold the material. Patching overhead or on a vertical face with a stiff mix is slow work, and rushing it produces a patch that sounds hollow within a year.

Keeping Water Out

Water reaches a concrete wall from three directions: through the soil face, through the top, and through the exposed face. Each has a different control.

Soil face. The waterproofing membrane or coating applied during construction is the primary barrier. It is not renewable without excavation, which is why the drainage detail matters so much.

Top. The grade behind the wall should slope away, and the wall top should have a cap or a shaped detail that sheds water. Soil piled against the top of the wall is a direct path in.

Exposed face. A penetrating silane or siloxane sealer reduces absorption without trapping vapour. Film-forming sealers can blister when moisture behind them tries to escape, so they are usually the wrong choice on a retaining wall.

None of these substitutes for drainage. A gravel layer and a working perforated pipe relieve the water before it ever reaches the concrete, and they cost $5 to $15 per square foot.

Joints and Efflorescence

Control joints are supposed to open, so the sealant in them is a wear item. Check each joint annually, cut out failed sealant, and replace it with a flexible joint sealant. A joint that has opened wider than the sealant can span needs a backer rod and a larger sealant profile.

Efflorescence is cleaned with a stiff brush and a diluted acid or proprietary remover, then rinsed. It is cosmetic, but it is also a tracer: it shows where water is moving. Clean it, then find the water.

When to Bring In a Pro

Bring in an engineer for horizontal cracks, cracks over 1/4 inch, a lean of more than about 2 inches, or spalling that exposes significant lengths of rebar. Bring in a concrete repair contractor for epoxy or polyurethane injection, deep spall repair, and joint replacement.

The economic test is the same one used for walls generally. If the repair bid passes about 60 percent of replacement cost, replace instead. The problems guide explains which failure patterns fall on which side of that line.

A Five-Year Schedule

1. Year 1. Inspect, photograph, seal hairline cracks, and confirm the drain outlet discharges.
2. Year 2. Re-inspect the same locations, patch any new spalls, and clear the outlet again.
3. Year 3. Check joint sealant, replace failed sections, and clean efflorescence.
4. Year 4. Re-inspect, and have any crack that has widened injected by a contractor.
5. Year 5. Apply a penetrating sealer if the wall is in a freeze-thaw climate, and reassess the drainage.

For the repair methods behind each step, read retaining wall repair. For the drainage that does most of the work, see retaining wall drainage, and for replacement pricing when maintenance stops making sense, poured concrete cost.