5 Things About PU Injection Grouting

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18 March 2022 - 16:05, by , in PU Grouting, No comments

Cracks in your home are a common problem, but if left untreated, they can cause leaks, which can result in significant damage to your home. This can be fixed in many ways. The important thing is to find a solution that will prevent cracks from occurring again in the future. PU grouting may be one possible solution.

PU grouting, or polyurethane injection or grouting, is a waterproofing technique that injects polyurethane, a fluid resin, to prevent water leakage through cracks or gaps in the concrete of the building structures. It can be confusing because the process may be called by different names within the industry such as PU grouting, PU injection repair, PU waterproofing, PU injection grouting, but the procedure is the same. 

Its short curing time and low cost make PU grout an ideal solution for water leakage. As a result of its low viscosity, it is able to expand, sealing tiny cracks to prevent further leakage. Additionally, the resin retains its flexibility after injection, allowing subsequent movement in the structure while keeping the gaps sealed.

To fully understand the method of PU waterproofing, it is essential to first understand the causes of cracks in the first place, to give you a better idea of how PU waterproofing can help protect your home and property.

1) Cause of Cracks on Walls

Knowing what causes your structural cracks will help you determine the best solution to your leakage problem. Common crack causes include:

  • Bad Drainage
    Water is the main reason for building cracks. A bad drainage system allows water to seep through, causing building materials to become unstable and to wear away. If you plan to have PU injection grouting to repair the cracks in your property, it is also vital that you check if your drainage system is working properly.
  • Heavy Load
    In industrial areas, heavy load due to movement of machinery and vehicles like forklift trucks and lorries can cause cracks to form on the concrete after a while. Cracks will be more severe in areas with a high volume of traffic. Structures with tin roofs can experience leaking of water onto the flooring, and this together with a heavy load may lead to cracks, holes, and gaps.
  • Wear Tear
    If the structure is not well-maintained, cracks will appear due to wear and tear that happens as the structure ages. This is especially true in areas like roofs, balconies, and other damp areas usually exposed to water and humidity.

2) Process of PU Injection Repair

PU grouting, as mentioned earlier, is one of the most recommended waterproofing techniques. Following are the steps for PU waterproofing; though it should be done by professionals with professional equipment.

  1. Cleaning
    Cleaning helps the technician to check and analyze the area and determine the location and spacing of the holes. It also removes mineral deposits left from the water leakage.
  2. Drilling
    To inject the resin into the crack, drilling is a crucial process for the injection holes. The angle while drilling should be 45 degrees or less towards around 2/3 of the structure’s thickness. There should be a 20 cm to 30 cm drilling space between the holes.
  3. Insert Packers
    The technician will place a grouting nozzle injection packer in the drilled hole. They will also tighten it with a special hexagon wrench, leaving no gap between the nozzle and drilling hole for the water to leak into.
  4. Seam Cleaning
    Using a high-pressure cleaning machine, the technician will inject clean water into the mechanical packers, at the pressure of 6Mpa, to clean the dust in the seam of the area.
  5. Sealing Cracks
    The surface of the leaking cracks is sealed with a cement-based waterproof material during the washing stage so that the polyurethane will not seep out.
  6. Grouting
    Using a high-pressure injection grouting machine, the technician will inject the polyurethane into the hole. They will elevate the grouting machine bottom-up and start injecting the resin one hole at a time.
  7. Removing the Packers
    After grouting, the grouting nozzle will be removed by the technician if there is no more leakage and will then proceed to clean up the irrigation fluid that may have spilled and solidified.
  8. Sealing
    The technician will then repair and seal the injected area of the concrete with cement-based waterproof material.
  9. Waterproofing
    To fully fortify the area, the technician will smear the grouting area with a single component waterproof material, with a 10-20 cm width and 20-30 cm length at both ends.

PU Injection process

3) Advantages of PU Injection Repair

There are many ways to repair leaks, including PU grouting. You will however be able to take advantage of PU injection’s benefits over other waterproofing methods. PU injection has the following benefits:

  • Polyurethane is a versatile resin that can also be used for coating, maintenance, emergency repair, and insulation purposes.
  • It is a strong adhesive, which protects the concrete from building movement and exposure to sunlight, which makes it a suitable material for surfaces such as roof and balconies.
  • It is fast drying and can seal small cracks on the surface.
  • PU injection repair comes with a low construction cost.
  • This method requires little to no maintenance.

4) Different Types of Injection Grout

As well as polyurethane, you can choose from other types of grouts. Each type of grout has its own purpose. Understanding the characteristics of each is vital to making sure you are using the right type for your leak repair. Among the other types of grout you can use are:

  • Cementitious Grouts
    Cementitious grouts are the traditional grouting material for residential applications. It is composed of cement and water, with admixes or additives, based on its purpose. If used for porous tiles (quarry, slate, or natural stone tiles), there is a possibility of this grout staining the surface.
  • Epoxy Resins
    Epoxy resin contains resin and hardener, making it less porous than cementitious grouts. It does not bond well with wet surfaces, but it adheres well to metal, concrete, and ceramics. It is a perfect choice for areas with acids and greases like the kitchen because it is strong and resistant to chemicals.
  • Acrylic Resins
    Acrylic grouts form a permanent gel, with low adhesive and compressive strength, but high tear strength. Additives can be added to the mix to hasten or prolong the reaction of it. It is the usual choice for architectural coatings and product finishes.

PU Injection process

5) PU Grouting vs. Hacking

For cracks and leak repairs, PU injection grouting is a hassle-free and cost-effective solution. There is no need to hack away your floor or walls because it only involves inserting resin into cracks in concrete. In addition to having your home items covered in dust, spending money on new tiles and wall paint, and making constant noise while hacking, hacking methods can cause additional issues. This is not the case with PU waterproofing. You will save a lot of money, since it is a less labor-intensive, safer method.


Aside from waterproofing, the company also offers other services such as painting and coating, minor works in construction, and other general contract work, to ensure that ceiling leak will not be a problem for a long time. Singapore Waterproofing is a reliable waterproofing company that delivers high-quality service every time. 


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