Polyurethane (PU) injection or grouting is a type of waterproofing solution to solve problems not limited to only water leakage, but also concrete cracks, depressed concrete slab, and settlement problems due to its high expansion properties and short reacting period. PU resin is a type of fluid resin that can expand in the concrete structure, and thus produce the polyurethane foam and fill the cracks or voids on it. However, the physical properties of PU will change from liquid to solid after undergoing a specific chemical transformation process.

PU injection has short curing and repairing time, therefore, it is highly recommended to be adopted in sealing the visible active leaks observed in the concrete slabs. PU injection is a type of cost efficient waterproofing method to solve the leakage issue in residential properties, especially if the water is coming from the outside. For industrial properties, PU injection can be used to repair flooring which the area being damaged after repetitive use of heavy machinery.

Polyurethane (PU) resin possesses many characteristics that are effective for waterproofing. The flexible properties of polyurethane allow the movement of resins with the wall during contraction and expansion while keeping the voids sealed.  PU is a versatile polymer that can also be used in industrial applications such as surface coating and insulation purposes. Besides, its fast drying properties enable it to stop active leaks that may not be achieved using other waterproofing solutions. The PU injection also requires lesser maintenance and therefore cost of repairing works can be saved. For the cons part, PU injection is a corrective measure instead of a preventive measure like the other waterproofing solution. It repairs only places where leakages occur. Therefore, other locations with potential water leakage issues may not be prevented in advance. Subsequently, trained and skillful labor is required in the PU injection process in order to ensure the correct and effectiveness of the waterproofing.

Firstly, decide the location to conduct the PU injection and clean the area. Then, drill the holes at selected locations for PU injection at 45 degrees angle or less and the drilling depth should be around 2/3 of the structure thickness. Then, insert the packers into the holes. After that, inject the PU grout from the lowest packer by using a high-pressure injection grouting machine. High pressure will raise the polyurethane resin from the lower side of concrete to the upper side of the concrete. After the leakage has stopped, remove the packers and clean the exposed resins. Lastly, patch the drilling holes with cement-based waterproof materials.

Thermoplastic membrane is made of polymers such as polyvinyl chloride (PVC), chlorinated polyurethane, or chlorosulfonated polyethylene. The glass-reinforced PVC is the most popular type of thermoplastic membrane. It has a typical lifespan of 22 to 30 years.

The thermoplastic membrane has many advantages. For example, it possesses elongation properties and high resistance to chemical and hydrostatic pressure. It can also be applied at seams with ease with solvent-based adhesives or with the aid of heat-welding. It can also be cropped to accommodate application in places with irregular shapes. Figure 2 shows the thermoplastic membrane is cropped to cover a column. However, it also comes with some shortcomings. When it is subjected to high temperatures, its strength will be highly affected. Besides, it will be degraded when it comes in contact with hydrocarbon materials, like asphalt, fuel, and lubricant oil.

Application of the thermoplastic membrane requires the contact surface reasonably free from defects like a floor with a steel trowel finish to ensure good adhesion. It is usually not suitable to be implemented on the rooftops due to the hot weather. Hence, it is more suitable to be applied in cool places, such as tunnel structures and underground structures. Its good chemical and hydrostatic pressure resistance also allow it to be applied at ponds, swimming pools, and water tanks.

A thermoplastic membrane can be used to tackle water leakage issues. It has elongation properties, high chemical resistance, and high hydrostatic pressure resistance, but it will be weakened in high temperatures. Hence, it is suitable to be applied in cooler places, such as tunnels and water tanks. In this way, its strengths are fully utilized, and its weaknesses are effectively minimized.

A waterproofing membrane is a membrane layer laid over a particular surface to prevent water leakage. Bituminous materials are made by combining organic materials with bitumen. It is viscous, liquid, adhesive, and waterproof. These membranes are usually manufactured in roll form and properly sealed in the factory, which will then be unfolded on-site and applied on the intended surfaces with tar-based adhesive with the aid of blowtorches. The bituminous sheet membrane is generally applicable to most parts of the building structure. It could be applied at the rooftop, balcony, substructure, and outer walls where water accumulation might happen.

Without a doubt, a bituminous sheet membrane has good durability and a long lifespan up to 30 years. It also possesses high resistance against acidic corrosion and impact load. Other than that, it is elastic and can be stretched to cover small cracks. The membrane’s elastic properties also enable it to resist stresses caused by building thermal and structural expansion. For the cons part, the application of the bituminous sheet membrane involves high skilled labour as high-quality workmanship is needed to ensure proper sealing, lapping, and finishing at corners and edges. The applied surfaces must be ensured flat and smooth without any voids, protrusions, or honeycombs.

Some preparation works need to be done before the laying process of the bituminous sheet membrane can start. Firstly, clean the surface that needs to be covered with a bituminous sheet membrane. Before laying the bituminous sheet membrane, the membrane should be checked to ensure proper alignment and no wrinkles are allowed. During the laying process, the torch fire should be applied slowly and uniformly over the membrane roll. All lapping edges between two membrane sheets must be checked carefully to ensure proper adhesion and no air gaps are permitted. If air gaps are present, the respective sheets must be lifted and reinstalled. The membranes are recommended to overlap over one another for at least 3 inches at sides and 6 inches at ends.

Bituminous sheet membrane is the common waterproofing membrane used in the market nowadays. It is suitable for the concrete flat rooftop, underground structures, and also areas that are prone to moisture. It also has long lifespan up to 30 years as compared to its available waterproofing methods on the market. Its elastic properties not only cover any small cracks present on the surface but also enables it to resist stresses arising from thermal and structural expansion.

Cementitious waterproofing is one of the common waterproofing methods in the market. It uses polymer modified cement based coating to fill up the pores in the concrete and make the waterproof barrier. It is generally suitable to be applied in indoor areas such as kitchen floor, shower stall, bathroom floor, and underground structure where these places are shielded from the hot sun or less exposed to weathering, so thermal expansion and contraction processes are effectively prevented.

Cementitious waterproofing is a simple process and can be said that it’s the easiest waterproofing method to apply which the workers can simply apply with various tools, such as roller, brush, and trowel. It is durable, affordable, and readily available. However, proper mixing and enough layer thickness are required to form a good waterproof barrier. The quality of workmanship will directly affect the lifespan and typically last for 10 years, which is relatively low compared to the other waterproofing methods. Meanwhile, it has poor resistance to thermal expansion and contraction caused by movement joints.

Typically, cementitious systems are applied in two-layer coatings. Third-layer coatings are applied if additional protection is necessary. The cementitious waterproofing method is suitable to solve indoor water leakage problems due to its weak properties against thermal expansion and contraction. It is widely used due to its availability, low cost, and durability against chemical attacks.

Liquid-applied membrane can be easily applied by using a brush, spray, roller, trowel, or squeegee, and the solvent base typically contains urethane or polymeric asphalt (hot or cold-applied). The liquid-applied membrane is generally applicable to various types of structures and substrates, which can be applied at the rooftop, road, basement, and terrace. It is good in filling up cracks, gaps and voids to provide seamless protection.

The advantage of liquid-applied membrane is high strength and elasticity properties. It also has low in-place costs and can be easily applied at various surfaces. Its typical lifespan is around 25 years, which is relatively high compared to the other waterproofing methods. However, high-quality workmanship is required to assure the applied membrane’s thickness and uniformity. The possibility of air bubbles may occur as a result of improper substrate preparation. In addition, it has toxic and hazardous VOCs, so the workers’ healthcare needs to be concerned.

The liquid-applied membrane can effectively good to solve water leakage issues. It is particularly suitable at places with uneven surfaces or many complicated details. Its properties with high strength and elasticity as an advantages, however the obvious disadvantage is inconsistency in coverage. To ensure they can reach the minimum coverage, the applicator must take additional care when applying it.