10 March 2022 - 10:32, by , in Basement Waterproofing, No comments
  • Waterproof membrane refurbishment.
  • High-pressure leak sealing injection of hydrophilic polyurethane resin into floor/wall joint.


When we have a decent amount of rainfall, there are many buildings experiencing water ingress. Rooftops, basements, lift pits and underground car parks are particularly vulnerable during and after heavy rainfall or prolonged periods of rain.

When the soil gets saturated with rainwater, cold joints, floor/wall joints, cracks in concrete and masonry basement walls or floors can turn into active water leaks.

The hydrostatic pressure from the rising water table and the lateral pressure from saturated soil are pushing the excess water into basement slabs, foundations and retaining walls making them susceptible to water ingress through cracks, porous building materials, holes, joints and/or inadequate waterproofing.

hydrostatic pressure entry points. Typical water ingress points in basements

Typical water ingress points in basements.






Some common signs of water ingress:

  • Damp patches on plaster walls
  • Damp skirting boards
  • Discolouration and black spots of mould on inside walls, near skirting board
  • Peeling paintwork
  • Blistered (hollow sounding) plaster
  • A damp and musty odour


Mould or damp patches are not always visible and you may have hidden mould or damp if:

  • There is a mouldy/earthy odour
  • There is regular condensation indoors
  • The room feels regularly humid


This room (pictured) is situated in a partially below ground area of the house and our client had identified that they were experiencing water ingress in some areas of the room. Our Waterproofing Singapore inspector observed that there were signs of water ingress through the floor/wall joint and the walls.Water seepage into basement room through wall/floor joint and walls

Image: Water seepage into basement room through wall/floor joint and walls. You can see the water damaged skirting boards and parts of the lower areas of the walls.













  1. Surface preparation: Remove existing bitumen waterproofing membrane.
  2. Perform leak sealing injection into floor/wall joint.
  3. Install a reverse side cementitious waterproofing membrane to the walls in multiple layers on top of a primer system.
  4. Prime and seal the vertical gap in the wall with mastic joint sealant and apply membrane NSM100+.


  • Surface preparation of the walls: After the wall sheeting was removed to provide access, our leak sealing specialist mechanically removed the existing bitumen waterproofing membrane back to the substrate. Any holes and deep grout lines were filled with a suitable concrete repair mortar.


  • Leak sealing injection of floor/wall joint: Our leak sealing specialist intersected the joint at intervals and injected a flexible polyurethane at high pressure into the joint. After allowing the polyurethane to react and bind with any water present in the joint and surrounding concrete to form a flexible seal, the injection ports were removed, and holes filled with a suitable concrete repair material.


Polyurethane Concrete Crack Injections step by step.

Image: Example of leak sealing injection with polyurethane resin into a concrete wall.

The leak sealing process, or polyurethane injection, involves the high-pressure injection of flexible water-reactive polyurethane (resin) into targeted areas to form a durable seal. This system is ideal where a long-lasting waterproof seal is required to stop the passage of water or other liquids through gaps, cracks, joints, and penetrations – typically in concrete and masonry constructions.

It is a highly specialised process, requiring the skills of experienced operators. At Singapore Waterproofing our technicians perform polyurethane injection works frequently. They receive ongoing training from industry leaders which equips our technicians with expert skills and knowledge.

We use the best Polyurethane (PU) product available as our primary injection resin. This resin offers superior performance. Its main features include permanent flexibility; very low shrinkage; water potable; low viscosity; and a hydrophilic reaction – it is the same product that is pre-approved by major traffic authorities around the world for major infrastructure assets.

This system can be installed in any weather – in fact,  the wetter the better, as it reacts with water right before your eyes. In dry weather, flooding the source of water entry (where possible) may have a similar effect.

Singapore Waterproofing’ proprietary injection system exceeds the highest injection process and safety standards in Australia and internationally throughout Europe and the USA.

We continually review and reassess the method, always striving to hone and improve our systems. Our proprietary leak sealing system forms a long-lasting flexible seal against water ingress which also withstands normal building movement between construction elements and details.


  • Walls: After the leak sealing injection of the floor/wall joint was completed, a primer was applied to the wall before the reverse side cementitious waterproofing membrane (NSM100+) was installed in multiple layers.

Our waterproof membrane (NSM 100+) is a two-component acrylic modified cementitious coating that is flexible so that it can handle a small amount of movement.

This membrane is a hardwearing, seamless waterproofing membrane for effective concrete protection. It also provides an effective barrier to waterborne salts and atmospheric gases.

The NSM 100+ system is breathable. Whilst repelling water, it allows moisture to pass through it slowly as a vapour, allowing the substrate to breathe.

It is water-based, so any vapours are non-toxic and ideal for potable water usage and it can be painted over in water-based breathable paints (e.g. low sheen or matt acrylics) and most water-based after-trades such as direct stick, tiles or render.


  • Vertical gap: The vertical gap in the wall was primed and a backing rod was inserted, followed by the application of mastic joint sealant to fill and seal the gap. This area of the wall had additional applications of the cementitious membrane NSM100+.

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