Water Leakages

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Leak Types & Possible Causes


There can be numerous causes of leaks. Leaks can occur from the outset during and after construction. We can pinpoint the exact locations of water leaks in walls, roofs, showers, balconies, sub floors, concrete slabs, planter boxes, decks, water features, facade and plumbing.

Typical Home Owners

  • Water Leakage & Water Seepage
  • Roof Leakage
  • Ceiling Leakage

Landed Property Home Owners

  • Structural Leakage and Seepage
  • Architectural Leakage and Seepage

Water Leak Repair

Why do homes have water leakage and seepage problems?

Brand-new properties should not have water leakage or seepage problems if they are built right. However, as these properties aged, repair and maintenance become necessary. Homeowners need to take note of any water leakage or seepage issues in the house. When such problems are first noticed, call in an expert to take over so that there will be less disruption to your daily life.

What are the water leakage and seepage problems faced by homeowners?

 Typically, homeowners are faced with the following concerns in their homes:

What is the most common leakage problem in Singapore?

The primary leakage issues faced by Singapore homeowners are cracks in their internal and/or external walls. While some contractors may tell homeowners that evacuation is necessary, we at Le Fong, have a better solution for you – Polyurethane (PU) Crack Injection.

What is a polyurethane (PU) crack injection?

A PU Crack Injection is a kind of repair work and waterproofing technique that is applicable only to poured concrete structures. The method makes use of a pressurised injection of resin (a type of waterproofing material) into a foundation crack. The pressure of the injection ensures that the entire crack is filled. That efficiently eliminate the crack and prevent water from coming into the house through your ceiling or basement.

This is the best solution for a crack found in a poured concrete wall. It is also economical as a form of repair work for a leaking concrete wall in your house or basement.

PU injection involves concrete crack repair and basement waterproofing techniques which are only applicable to poured concrete structures. Crack injection, or PU Injection, is used in the following applications:

  • To repair water seepage from  concrete cracks of virtually any size in poured concrete walls or ceilings;
  • To permanently seal actively leaking  cracks;
  • To repair basement cracks that have been previously repaired by injection or some other basement waterproofing technique; and
  • The repair of cracked poured concrete structures in general.

How does crack injection work to fix water leakages?

PU injection involves the pressurized injection of either epoxy or polyurethane resin into a foundation crack; these injections are referred to as epoxy crack injection and polyurethane crack injection. The injection pressures ensure that cracks are filled through the entire thickness of a ceiling wall which is typically 200-300cm thick, thereby effectively eliminating the crack and keeping water on the exterior of the foundation where it belongs so that you no longer have water in your basement. This type of concrete crack repair is all that is needed to accomplish basement waterproofing when a poured concrete crack is leaking, or if there is a concern that an existing crack may leak in the future. Pressurized crack injection is also the most economical means by which to repair a wet, leaky poured concrete basement; in reality, it is rarely necessary to excavate a poured concrete foundation wall.

Excavating and waterproofing a foundation is expensive and destructive. Crack injection is an effective and inexpensive way to put an end to foundation leaks and that wet basement.


We are well known among homeowners, waterproofing contractors, renovation contractors, and property managers in the Singapore, and surrounding areas, as the “Concrete Crack Injection Specialists” because we are the indisputable leaders in the domain of pressurized injection services for concrete foundation crack repair / foundation crack injection in both residential and commercial applications.

As the indisputable leaders in the domain of pressure injection services for concrete crack repair and crack injection in residential, commercial and industrial properties, we are the experts for any of your water leakage or seepage problems due to cracks on your internal and/or external walls.

Our experienced specialists are the leaders in the industry because of four key reasons.

  • We use the latest technologies and techniques;
  • We use highly customized equipment;
  • We use a variety of epoxies and polyurethanes that are the most appropriate for a given application; and
  • Our technicians undergo rigorous training before they can qualify to become journeymen and injection technicians.

Latest Technology and Techniques

We use only the latest technology and techniques

Highly-customised Equipment

We use highly-customised equipment that is not found in the market

Appropriate Materials

We have a variety of materials available to us and use only the most appropriate one for each job. We do not believe in a “one size fits all” mentality.

Qualified Technicians

We rigorously trained our new technicians before they are qualified to work alongside our experienced experts in the PU Crack Injection team.

It’s a fact, some of our competitors call us to do their foundation crack repairs and basement waterproofing in situations that they just can’t seem to resolve. With many of successful injections behind us, we have proven that we are able to handle the concrete foundation crack in your wet basement or any other cracked concrete underground structure.

We are the rescue team for water leakage and seepage issues. Even some of our competitors come to us when they are not able to solve the problem on their own.

Le Fong has proven our expertise in handling any cracks in the concrete foundation of your ceiling, basement or any other underground structure with all the success of our PU Crack Injections behind us.

De Neef®

Denepox 40

Structural Injections

Structural cracks

  • Overloading of the structure
  • Collision damage
  • Non compensated concrete shrink
  • Structural bearing capacity of the structure compromised
    – Usually small cracks
    – 0.2 to 1 mm
  • CE-marking for concrete injections required  Denepox 40
  • Cracks of 0.2 to 1 mm
  • Injection with high strength epoxy resin
    – Denepox 40
  • 2-component resins
    – Injected as single component
    – After mixing
    – Long pot life
  • Pure resins
    – Only for small cracks
    – Otherwise resins become too hot
    – Boils and degrades

Denepox 40

Pure epoxy resin

Dry or moist applications

Pot life (20°C) : 80 minutes

High structural strength

Tensile strength : 60 N/mm²

Compressive strength : 100 N/mm²

Adhesion to moist concrete : More than concrete cohesion

Low viscosity : 80 mPa.s

Deep penetration in small cracks


2 injection methods

High pressure / low flow

  • Screw down packers
  • Slow
  • Dangerous to cause more damage

Low pressure (2-3 bars)

  • Adhesion packers
  • Faster
  • Les critical on damaged structures

Mix quantities and pot life

  • Epoxies when mixed have an exothermic reaction
  • The more volume, the faster and stronger heat development
  • Pot life is much reduced with rising temperature
  • Product becomes very hot and can start fuming
  • Only mix small quantities that can be injected within the time to avoid heat building up
  • Refer to manufacturer recommendations
  • Eg : Denepox 40 has 80 minutes pot life
  • Only mix 600 g batches for crack injection
  • Use within 60 minutes at 20°C

High pressure injection

  • Install packer
  • Laced grid
  • Distance between holes depends on crack size
  • 45° angle until half substrate depth
  • Single component injection
    – Hand pump
    – Electrical pump
  • Lowest possible pressure
  • Inject from packer to packer to assure fill

Low pressure injection

  • Install the adhesion packers
  • Direct onto the surface using polyester paste
    – Or other fast suitable adhesive
  • Seal crack surface with adhesive
  • Distance depends on crack size
    – On average 10 cm spacing
  • Single component injection
    – Diaphragm pump for low pressure
    – Maximum 2 to 3 bars
  • Inject from packer to packer

De Neef® Injections

Special Techniques

Expansion joints with HA Safefoam NF

Expansion joints

  • Technically most difficult part to waterproof when leaking
  • Filling material needs to have following properties
  • Adhesion to sides
  • Correct modulus of stretch
  • Force to stretch material with opening joint < adhesive strength
  • Otherwise delaminates from sides
  • Resist compression when joint closes
  • Traditional method for open joints
  • GASFAR system
  • Only when joint is accessible from top

Alternative to GASFAR

  • Current version of HA SafefoamNF
  • Hydrophilic PU resin
  • Adhesion to wet or moist joint sides
  • Not possible with hydrophobic resins as they skin over and don’t penetrate concrete pores
  • Very ductile material in correct application
  • Assure 1/1 mixing ratio with water
  • Water filled joint
  • Inject 1/1 with 2C pump
  • Good adhesion to concrete
  • On average 1.4 MPa
  • For reference 2 MPa is considered structural bond exceeding concrete cohesion
  • Internal test report available


  • Injection at back of joint
  • Need to be allowed to drill through waterstop
  • Often difficult for engineers
  • Is failing already.

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Protect your home and office with our Waterproofing Solutions.

De Neef®

Gelacryl AR

(Acrylic Rubber)

Gelacryl AR

Gelacryl AR to reduce shrink in dry conditions

  • Poly-acrylate gels
  • Only in continuously humid conditions
  • In dry conditions shrink up to 75 % and loss of elasticity (80 days)

No changes in other properties

  • Remains more elastic when dry.
  • No glassification of the cured compound
  • Improved mechanical properties
  • Improved characteristics for injection into wet areas

Gelacryl Superflex AR applications

  • Screen injections behind structure for waterproofing
  • Screen injections behind masonry structures
  • Soil stabilisation (= coagulation)
  • Screen injections behind tunnel segments
  • Sealing tunnel liners (Superflex)
  • Moving cracks (elongation)
  • Sealing capillaries with small movements

In Applications with:

  • Fluctuating ground water levels
  • Wet – Dry conditions
  • Cracks open to the air


Gelacryl Superflex Resin – TE300


Gelacryl AR2 – SP200

  • Predosed set
  • Packaging adapted with coloured stoppers
  • Same method of formulation as standard Gelacryl Superflex

IP 2C-Gel = pneumatic pump

  • 2 pistons 1:1, powered by 1 airmotor
  • Separate flushing pump
  • Stainless Steel construction
  • Pressure up to 200 bar
  • Flowrate 14 l / min
  • Durable, easy cleaning
  • Low maintenance


Injection head

  • 2-component
  • Separate flushing system
  • Integrated true static mixer
  • New compact design
  • Easy to use and manipulate
  • Improved design of the non-return valves
  • Suitable for all Gelacryl system and CementGel W


Gelacryl AR

  • Same as standard Gelacryl injection
  • SP 200 needs to be mixed thoroughly in the AR2 component
  • Very suitable for crack injection, even larger cracks
  • => standard Gelacryl less suitable due to changed dry properties
  • Flushing requires more water to clean the AR2 piston on the pump
  • Used for injections into concrete joints and cracks
  • CE marked as a system.
  • Not just single components
  • Gelacryl Superflex AR CE marking
  • What does U (S2) W(1) (1/2/3) (5/40) mean:
  • U = intended use
  • S2 is resistant to pressures of 7 bars
  • W = crack width
  • 1 = starting from 0,1 mm
  • 1/2/3 = moisture state of crack
  • 1 = dry
  • 2 = damp
  • 3 = wet
  • 5/40 = range of application temperatures

Gelacryl Superflex AR system components

Concrete floor joint injection with Gelacryl Superflex AR

Cured Gelacryl Superflex on concrete surface


  • 1-component polyurethane resins are not suitable for this application
  • 1-component polyurethane resins are not void fillers
  • No confinement gives no garuantee of waterproofing
  • Needs adhesion to sides of joint
  • Development of new injection technique using standard resins available

Definition of large joint

  • X = Joint opening
  • Joint opening is minimum 4 – 5 cm
  • Size of Reinforcement Foam side widths
  • Or multiplication of this
  • Reinforcement Foam is mounted side by side

Definition of limited dilation

  • Y = Dilation of the joint
  • Opening or closing
  • Maximum 30 %

Installation of Reinforcement Foam

  • Build-up of waterproofing barrier must be correctly dimensioned
  • Observe enough free space to allow barrier expansion
  • Install injection tube in the middle between the foam
  • Make sure end pieces come above joint level


GASFAR installation

Lost formwork at bottom of joint   = Prevent large water inflow and resin dilution during injection

  • Cartridge foam
  • Pipe Plug / Dry Oakum / Impregnated rags
  • Closed cell backer rod for confinement
  • Clean the sides of the joint to assure proper adhesion of the GASFAR system


Maximum distance determined by gel time used

  • If possible, inject in 1 pass
  • Otherwise, create temporary forms between injection stages

Installation of Reinforcement Foam

  • Build up of the leak sealing solution
  • As much material as possible in the design of the joint
  • Respect an open space on top to allow for post-expansion of the gel
  • Install a SIS tube in the middle between the Reinforcement Foam
  • Injection ports need to protrude above the surface


Installation of top formwork

  • Creates injection pressure and improves adhesion
  • Cartridge foam
  • Closed cell backer rod
  • Wooden form


Injection ports need to rise to the surface



IP 2C-Gel = pneumatic pump

  • 2 pistons 1:1, powered by 1 airmotor
  • Separate flushing pump
  • Stainless Steel construction
  • Pressure up to 200 bar
  • Flowrate 14 l / min
  • Durable, easy cleaning
  • Low maintenance

Injection head

  • 2-component
  • Separate flushing system
  • Integrated true static mixer
  • New compact design
  • Easy to use and manipulate
  • Improved design of the non-return valves
  • Suitable for all Gelacryl system and CementGel W



Use Gelacryl Superflex AR

  • Reaction time set to fit the injection
  • The full joint
  • The compartiment in case of a segmented injection


Finishing the joint

  • Close the surface to keep the joint clean and moist
  • Colflex tape
  • Backer rod + Caulk
  • Non foaming poured polyurethane resin

Open joints in precast underpass

  • Open joints in bicycle tunnel
  • Bituminous membrane leaks
  • Filled with non expanding caulk which also fails

Drainage connectors to shafts

  • Old drainage replaced
  • PVC Connectors

Drainage connectors

  • Injection of Reinforcement foam with Gelacryl Superflex AR
  • No injection tube, conical packers directly into the PVC part

Points to remember/consider

  • Always install sufficient material to do the job
  • 5 to 10 cm high minimum
  • Reinforcement Foam sits loose into joint
  • Shallow joints : Curtain grouting or HA Safefoam NF behind waterstop
  • Always leave sufficient free headspace
  • Allow the material to swell when wet (150% afterswell)
  • Allow material to be compressed without coming out of joint
  • Joint need to remain moist, do not allow to dry for long periods : Finish joint with system to close
  • Colflex tape
  • Often used in Europe : Flame retarding mastic (public buildings)
  • Avoid water filling joint from top
  • The system was designed to keep water out of the structure, not in the structure
  • Injection system
  • Avoid pouring the premixed gel
  • Pot life can be reached without noticing