What is construction joint waterproofing?
Construction joint waterproofing blocks the path water takes along the plane between two pours. In new work, this is done with waterstops cast into both pours (PVC or rubber profiles), hydrophilic strips that swell on contact with water, or injection hoses placed in the joint so resin can be injected later if needed. The joint surface is also prepared by removing laitance so the new concrete bonds well.
In existing structures, leaking joints are sealed by PU injection along their length. Where the joint also moves, a flexible tape system such as Combiflex can be installed over it.
Benefits
- Blocks the most common leak path in below-ground structures
- Low cost when detailed during construction
- Re-injectable hose systems allow future sealing without drilling
- Linear leaks in existing joints sealed without excavation
Common problems and applications
Problems it solves
- Long horizontal leaks at the raft-to-wall kicker joint
- Leaks at wall lift joints in retaining walls and tanks
- Cold joints caused by delays during concrete pours
- Seepage between slab bays in podiums and basements
Where it is used
- Raft-to-wall kicker joints in basements
- Retaining walls and shear walls cast in lifts
- Water tanks, STP tanks and swimming pools
- Lift pit walls and sumps
Our construction joint waterproofing process
Joint planning
For new work, we confirm joint locations in the pour sequence and choose waterstop type for each.
Fixing waterstops
PVC waterstops are fixed centrally in the joint and supported so they stay in place during the pour; swellable strips are bonded to the prepared surface.
Joint preparation
Laitance is removed and the surface roughened before the next pour.
Injection hoses where specified
Hoses are fixed along the joint with outlets brought out for later injection.
Repair of leaking joints
For existing joints, PU injection grouting is carried out along the full length.
Overlay for moving joints
Where movement is present, a tape system is installed over the joint after injection.
Materials and systems used
- PVC and rubber waterstops
- Cast into both pours to physically block water.
- Hydrophilic swellable strips
- Bonded in the joint; swell to seal on contact with water.
- Re-injectable hose systems
- Allow resin injection after casting if a joint leaks.
- PU injection resins
- Seal leaking joints in existing structures.
- Tape systems
- Such as Sikadur-Combiflex, for joints that move.
Products are selected from the approved specification. Coverage, thickness and curing follow the manufacturer's current data sheet.
Why professional waterproofing is important
Construction joint detailing costs very little compared with the concrete around it, but it is often skipped under programme pressure. The result is the classic basement with a wet line around its perimeter at kicker level.
A professional waterproofing contractor plans joints with the civil team, fixes waterstops so they do not fold during the pour, and inspects before concrete goes in. For existing joints, injection along the full length, not only at visible wet spots, gives a durable seal.
Why choose us
- Planned with the pour sequence
- We work with the site team so waterstops are fixed before each pour.
- Inspection before concreting
- Waterstop position and continuity are checked and recorded.
- Full-length injection repairs
- Existing joints are treated along their length, not spot by spot.
- Tape systems for moving joints
- Combiflex installation by trained crews where movement is expected.
Read more about our team and how we inspect and record work.
Frequently asked questions
How do you stop a leaking construction joint in a basement?
Leaking construction joints in existing basements, tanks and lift pits are usually sealed by PU injection grouting along their full length from the inside, not just at the wet spots. Crystalline treatment can then be applied over the joint. If the joint also moves, a flexible tape system is installed over it after injection.
What is the difference between a construction joint and an expansion joint?
A construction joint is where one pour meets another; it is not designed to move. An expansion joint is a deliberate gap that allows movement. They need different treatments. See expansion joint waterproofing.
Which waterstop is better, PVC or swellable?
PVC waterstops physically block water and are robust when properly fixed. Swellable strips are easier to install but must be protected from early wetting and correctly confined. The choice depends on the joint and the specification.
Can a leaking kicker joint be repaired from inside?
Yes. PU injection along the full joint length from inside usually stops the leak. Crystalline treatment can then be applied over the joint.
