Replace failed concrete-joint sealant
Renew a level slab joint with flexible sealant and correctly fitted backing.
Home · 2–4 hr + cure · Medium
Before you start
Block the area from traffic. Wear eye protection and chemical-resistant gloves. Use hand tools rather than uncontrolled grinding; do not cut into concealed membranes or remove the full-depth joint filler. Follow ventilation and cleanup precautions on the sealant label.
Tools and materials
- Exterior self-leveling concrete joint sealant, compatible closed-cell backer rod and masking tape
- Hand scraper, utility knife, vacuum, blunt backer-rod tool, caulking gun, gloves and eye protection
Check the problem
Check joint shape and movement
Measure width and depth and inspect for unequal slab heights or crumbling edges. Self-leveling material will flow downhill; use a different specified system for sloping joints.
Choose sealant and backing together
Match the joint width, movement and exposure to the sealant specification. Backer rod sets depth and prevents bottom adhesion; its diameter must fit snugly without damage.
Steps
Remove the failed sealant
Cut and lift out old sealant from the bonding faces with controlled hand tools. Remove deteriorated backing near the surface only; preserve deeper expansion filler and any membrane.
Clean and prepare the faces
Remove residue, loose particles and contaminants. Vacuum and achieve the dryness required by the selected sealant. Apply primer only if that system requires it.
Set the backer rod depth
Press an unbroken rod into the joint with a blunt tool, without stretching or puncturing it. Use the specified width-to-depth geometry; do not fill a deep joint solid with sealant.
Mask and dam open ends
Mask adjacent concrete if useful and close open joint ends with compatible temporary dams. Confirm there are no gaps where liquid sealant can escape below the intended depth.
Apply one continuous fill
Dispense slowly along the joint, keeping sealant in contact with both sides and avoiding air pockets. Let it level to the specified recessed profile. Do not overfill onto the walking surface.
Cure and check the bond
Remove masking at the instructed stage and protect from rain and traffic for the stated cure period. Inspect for voids, edge separation or an unwanted ridge; repair defects using the sealant maker’s method.
Remove masking at the instructed stage and protect from rain and traffic for the stated cure period. Inspect for voids, edge separation or an unwanted ridge; repair defects using the sealant maker’s method.
Tips
Backing saves more than sealant
Three-sided adhesion restricts movement and can make a new joint tear.
Read the actual label
Different versions of similar products have different moisture and cure limits.
Let it flow
Self-leveling sealant is not a substitute for non-sag caulk on a slope.