PU Injection / PU Grouting Singapore: What Homeowners Need to Know About Waterproofing Leaks
- waterseepagesg
- May 29
- 3 min read
Updated: Jul 8
Water seepage is one of the most common problems affecting HDB flats, condominiums, landed houses and commercial buildings in Singapore.
Whether the leak appears on a ceiling, wall, basement, planter box or roof slab, simply repainting the affected area will not solve the problem. Moisture continues travelling through tiny cracks inside the concrete until it finds another exit.
One of the most effective non-hacking waterproofing methods used today is PU injection, also known as polyurethane grouting.
At Seepage Solutions, we combine thermal imaging leak detection with professional PU injection waterproofing to locate hidden leaks accurately before sealing them from within the concrete.
What Is PU Injection?
PU injection, or polyurethane grouting, is a waterproofing method used to stop active water seepage within concrete structures, walls, ceilings, and cracks.
The process involves:
drilling small injection points along affected areas
inserting injection packers
pressure-injecting polyurethane resin into cracks or voids
Once injected, the PU material expands and reacts with water to form a waterproof seal within the concrete.
Unlike surface coatings, PU injection repairs the leak inside the structure, making it highly effective for active water seepage.
Where Is PU Injection Used?
PU grouting is commonly used for:
Ceiling Water Leaks
Leaks from bathrooms, roofs, balconies, or planter boxes can cause staining, peeling paint, and concrete damage.
Toilet Waterproofing
PU injection is often used as a non-hacking waterproofing solution for leaking bathrooms.
External Wall Seepage
Rainwater can penetrate cracks in external walls and cause internal dampness.
Roof Waterproofing
Flat roofs and concrete roofs may develop cracks that allow water seepage during heavy rain.
Basement Waterproofing
Underground structures often require PU injection to stop active water ingress.
Spalling Concrete Repair
Water seepage can corrode steel reinforcement bars and cause concrete to crack or fall.
Benefits of PU Injection Waterproofing
Non-Hacking Solution
PU injection can often be carried out without removing tiles or major demolition work.
Fast and Effective
Most PU injection works can be completed relatively quickly compared to conventional hacking methods.
Stops Active Water Seepage
Polyurethane resin expands and seals water pathways inside the concrete.
Cost-Effective Waterproofing Method
PU grouting is usually more affordable than full replacement works.
Suitable for Many Property Types
Used in:
HDB flats
condominiums
landed houses
commercial buildings
industrial properties
PU Injection vs PU Coating
Many homeowners confuse PU injection with PU coating, but they serve different purposes.
PU Injection | PU Coating |
Stops active leaks inside concrete | Protects surface from water penetration |
Injected into cracks and voids | Applied onto surface |
Used for seepage repair | Used for preventive waterproofing |
Suitable for leaking walls and ceilings | Common for roofs and exposed areas |
In many projects, both methods may be used together for long-term waterproofing protection.
How PU Injection Waterproofing Works
A typical PU injection process includes:
Site inspection and leak assessment
Identification of crack lines or seepage areas
Drilling of injection points
Installation of injection packers
Pressure injection using polyurethane resin
Allowing resin to cure and expand
Removal of packers and patching works
Replastering and repainting if required
The correct diagnosis of the leak source is important to ensure effective waterproofing.
Why Waterproofing Fails in Singapore
Common causes include:
ageing waterproofing membrane
cracked concrete
poor workmanship
thermal movement
heavy rain exposure
water ponding
failed sealants
structural movement
Singapore’s weather conditions can accelerate waterproofing deterioration over time.
Frequently Asked Questions
Is PU injection permanent?
PU injection can provide long-lasting waterproofing results when the leak source is correctly identified and treated.
Is PU injection better than hacking?
For many seepage issues, PU grouting is a faster and less disruptive non-hacking solution.
Can PU injection stop ceiling leaks?
Yes. PU injection is commonly used for leaking concrete ceilings and wall seepage.
How long does PU injection take?
Depending on the severity of the leak, most projects can be completed within one to several days.
Is PU injection suitable for roofs?
Yes. PU injection is commonly used for cracked concrete roofs and roof slab seepage.
Request a PU Injection Inspection
If you are experiencing:
water seepage
leaking walls
ceiling leaks
mould growth
spalling concrete
roof waterproofing issues
Contact Seepage Solutions for professional inspection and waterproofing solutions in Singapore.
We provide PU injection, leak detection, roof waterproofing, wall seepage repair, and concrete waterproofing services for residential and commercial properties.
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