Seal a small concrete crack
Keep water out of a narrow, stable crack in a nonstructural outdoor slab.
Lawn & garden · 1–2 hr + cure · Easy
Before you start
Stop for widening cracks, vertical movement, exposed reinforcing steel or a sinking slab. Do not grind or dry-cut concrete for this repair. Wear eye protection and gloves; keep people off the wet repair until the product permits traffic.
Tools and materials
- Exterior pourable concrete crack filler rated for the measured width and approved backing for deep cracks
- Stiff brush, dust-controlled vacuum, scraper, measuring gauge, gloves, eye protection and barrier
Check the problem
Check width and movement
Measure the widest point and compare both sides with a straightedge. Height difference, ongoing widening or major branching needs assessment beyond filling.
Choose the correct filler
Select a pourable product for horizontal, stable cracks of this width. An expansion joint or moving crack needs a different system.
Steps
Plan a dry work window
Check the label’s temperature, rain and traffic restrictions. Block off the area before cleaning.
Remove loose material
Brush away dirt and loose particles without widening the crack or grinding the slab. Vacuum with suitable dust control.
Clean and dry as specified
Remove contaminants by the filler’s approved method. Let the crack reach the required dryness; water hidden inside can prevent bonding.
Prepare the filler
Shake or mix exactly as directed. Check whether this depth requires the maker’s permitted backing or staged applications; do not improvise deep fills.
Fill neatly
Apply a controlled stream into the crack. Allow only the slight overfill the label specifies for shrinkage, not a broad trip ridge. Follow the label for settled areas and repeat-coat timing.
Cure and inspect
Keep traffic and water off for the specified period. Check that the fill is bonded and continuous without a trip ridge. Monitor for reopening; filling does not fix ground movement.
Keep traffic and water off for the specified period. Check that the fill is bonded and continuous without a trip ridge. Monitor for reopening; filling does not fix ground movement.
Tips
Expect a visible repair
A filler will rarely match aged concrete exactly.
Sealing is not structural repair
It reduces water entry; it does not restore a failed slab.
Reopening is a warning
Investigate the cause instead of repeatedly pouring more filler.