Waterproofing Cape Town

+27 (0) 21 300 9899

+27 (0) 61 518 4148


Bloubergstrand, Cape Town

waterproofing cape town

Polyurethane Waterproofing

Polyurethane Waterproofing

polyurethane waterproofing


Polyurethane waterproofing is a type of waterproofing coating that helps to protect construction surfaces against water ingress. This is important because water damage can lead to serious structural problems, and in some cases, it can make buildings or infrastructures unsafe. In this article, we will explore what Polyurethane waterproofing is, its importance in construction, and its brief history.

Definition of Polyurethane Waterproofing

Polyurethane waterproofing is a protective coating used on concrete surfaces that helps prevent the penetration of water. This coating consists of a two-component system; the first component contains polyol resin while the second component contains an isocyanate hardener. When mixed before application, they form a chemical reaction which creates a durable, flexible, and seamless membrane over the surface.

Importance of Waterproofing in Construction

Waterproofing plays an integral role in preventing damage to buildings and infrastructures caused by water intrusion. Water can seep into buildings through cracks or joints in walls, roofs or floors leading to mould growth, corrosion of reinforcement steel bars compromising structural integrity and eventual collapse if not addressed on time. In addition to preventing structural issues, waterproofing also helps keep indoor environments dry and comfortable for people working or living inside the building. It reduces maintenance costs by minimizing water-induced damage like roof leaks which may require expensive repairs down the line.

Brief History of Polyurethane Waterproofing

The use of polyurethane for waterproofing dates back several decades when it was first introduced as a two-component system for roofing applications. Since then, technological advancements have enabled its formulation into several types such as preformed membranes and liquid applied membranes (LAMs), making it possible for use across many areas like basements, roof decks, among others. Over time polyurethane formulations have improved and are now more resistant to chemicals, UV damage, and other environmental elements. The technology has come a long way from its initial applications, and it is now widely used in the construction industry due to its durability, cost-effectiveness, and efficiency in waterproofing buildings’ surfaces.

Types of Polyurethane Waterproofing

Liquid Applied Membrane (LAM) – Liquid Perfection
Liquid Applied Membrane (LAM) is a popular Polyurethane waterproofing system used in a wide range of applications such as roofs, floors, walls, and balconies. It’s a monolithic membrane that forms an impermeable barrier upon curing. This system is typically applied with a roller or spray gun which increases the speed and accuracy of the application.

Description and Application Process

The application process for LAM starts with surface preparation, which involves cleaning the surface and ensuring its smoothness before applying the primer. The next step is applying the primer layer to improve adhesion between the substrate and the Polyurethane coating. After priming, apply two coats of liquid membrane material on top of each other perpendicular to each other. Ensure that you follow manufacturer guidelines on thickness.

Advantages and Disadvantages

One advantage of LAM is its high elongation capacity, allowing it to bridge cracks that occur in substrates without compromising waterproofing performance. It also has excellent resistance to temperature changes, UV rays, and most chemicals commonly found in construction environments. However, LAM can be challenging to apply evenly due to its liquid nature; therefore, it’s essential that experienced professionals carry out this procedure.

Preformed Membrane – Tough Sheets

Preformed membranes are an alternative form of Polyurethane waterproofing systems developed from high-density polyethene materials (HDPE). They come in rolls or sheets designed for specific applications such as roofs or basements.

Description and Application Process

The installation process for preformed membranes requires close attention to detail during surface preparation. You must ensure that there are no protrusions or sharp edges on the surfaces where you will install the membrane. After surface preparation, you can apply the primer layer to improve adhesion between the substrate and the membrane. The next step is placing the sheet on top of the primed surface, ensuring that you overlap panels in a shingle-like fashion to prevent water from penetrating through seams. Ensure that you adhere to each panel correctly using a warm air gun or flame torch.

Advantages and Disadvantages

Preformed membranes are exceptionally durable, making them ideal for heavy-duty applications. They are also easy to install in sections and can be suitable for challenging surfaces such as roofs with awkward angles or corners. However, preformed membranes require exact measurements during installation since any deviation from recommended imperfections could compromise the entire system’s waterproofing abilities.

Advantages of Polyurethane Waterproofing


Polyurethane waterproofing systems are known for their exceptional durability. They can withstand harsh weather conditions and extreme temperatures without breaking down or deteriorating. This makes them ideal for use in both commercial and residential buildings, where they provide long-lasting protection against water damage. Polyurethane waterproofing systems also have excellent resistance to abrasion, impact, and other types of physical damage. This means that they can withstand heavy foot traffic and other types of wear and tear without showing signs of damage. In addition, polyurethane coatings are resistant to a wide range of chemicals, including acids, bases, solvents, and oils.


Another key advantage of polyurethane waterproofing systems is their flexibility. Unlike traditional roofing systems that may crack or split under pressure, polyurethane coatings can stretch up to 600% without tearing or breaking apart. This allows them to adjust to changing temperatures and movement within the building without losing their protective properties. The flexibility of polyurethane coatings also makes them ideal for use on irregularly shaped surfaces such as domes or arches. They can be easily applied over complex surfaces without the need for additional materials or special techniques.

Chemical Resistance

Polyurethane waterproofing systems are highly resistant to a wide range of chemicals, including acids, alkalis, solvents, oils, and fuels. This resistance is due in part to the fact that polyurethanes are made up of long chains of molecules that have strong chemical bonds between them. This chemical resistance makes polyurethanes ideal for use in areas where exposure to chemicals is likely – such as industrial buildings or chemical storage facilities. It also means that they are easy to clean and maintain over time – even if they become dirty from exposure to chemicals or other contaminants.

UV Resistance

One of the most key features of polyurethane waterproofing systems is their resistance to ultraviolet (UV) radiation from the sun. This is particularly important in areas where buildings are exposed to prominent levels of sunlight, as UV radiation can cause traditional roofing materials to break down or deteriorate over time. Polyurethane coatings are formulated with special UV stabilizers that protect them from the damaging effects of sunlight. This means that they can maintain their protective properties for many years without requiring frequent maintenance or repairs.

Polyurethane waterproofing systems offer a range of advantages over traditional roofing materials. They are exceptionally durable, flexible, chemically resistant, and UV resistant – making them ideal for use in a variety of settings and environments. Whether you’re building a commercial warehouse or a residential home, polyurethane coatings can provide long-lasting protection against water damage and other types of wear and tear.


Disadvantages of Polyurethane Waterproofing


Polyurethane waterproofing is an expensive solution for waterproofing compared to other traditional methods such as bitumen or acrylic coatings. The cost of polyurethane waterproofing is dependent on several factors such as the type of polyurethane system used, surface preparation, and application method. The liquid-applied membrane (LAM) system is more expensive compared to the preformed membrane systems due to its high application costs. However, despite being costly, polyurethane waterproofing systems offer excellent durability and provide long-term protection against water penetration, which can make it a cost-effective choice overall.

Difficulty in Application

Polyurethane waterproofing requires precise preparation and application techniques to ensure proper adhesion and effectiveness of the product. One common issue with polyurethane applications is improper mixing or application of the product. It requires a skilled technician to ensure that each component is correctly mixed and that the correct temperature and humidity levels are maintained during installation to avoid any issues with curing. Additionally, because these systems require specialized equipment for their application such as spray guns or rollers, they can be challenging for do-it-yourself projects. Therefore, it’s recommended that only professional contractors should handle these types of installations.

The Environmental Impact of Polyurethane Waterproofing

While there are no significant health risks associated with using polyurethane waterproofing systems once cured properly, improper handling and disposal methods can have environmental impacts. Some products contain volatile organic compounds (VOCs), which can be harmful if not disposed of properly or if exposed during installation. Therefore, proper safety measures must be observed when handling any chemicals associated with polyurethane products. While there are some disadvantages to using polyurethane waterproofing systems such as cost and difficulty in application, the benefits such as durability, flexibility, and chemical and UV resistance make it a popular choice in the construction industry. It’s important to note that proper installation and handling by trained professionals is critical to ensure the effectiveness and safety of these systems.

Application Process for Liquid Applied Membrane (LAM)

Surface preparation

Before the application of any waterproofing system, surface preparation is crucial. The surface should be free of oil, grease, dust, dirt, and any loose materials. The substrate should also be structurally sound and completely dry. Any moisture present on the surface can cause adhesion problems and create bubbles or blisters in the membrane. The ideal temperature for applying a liquid applied membrane is between 5°C to 35°C. Concrete surfaces need to be cured for at least 28 days before applying the membrane. Any cracks or voids should be filled with epoxy resin or polyurethane sealant before applying the primer.

Primer application

The primer provides better adhesion between the substrate and the LAM system. Polyurethane primers are usually used for concrete substrates while solvent-based epoxy primers are used on metal substrates. The primer application process involves mixing two-component primer using a drill machine with a proper mixer attachment until it reaches an even consistency. The mixed primer should then be applied using either a brush, roller, or spray depending on manufacturer specifications. It is important to follow manufacturer instructions as over-application of the primer can cause problems with adhesion and curing.

Application of the first coat

After allowing sufficient time for curing of the primer (usually 24 hours), you can start applying your first coat of LAM material using airless spray equipment or rollers depending on substrate configuration. It is important to apply a uniform thickness across all areas being waterproofed following maximum coverage rates recommended by manufacturers to avoid under-coating or over-coating that might lead to unevenness in coverage.

Application of the second coat

After allowing sufficient time (usually between 4-8 hours) after applying the first coat, the second coat can be applied following the same procedure used for the first coat. It is important to apply the second coat as soon as possible to avoid any material degradation or contamination. The final thickness of the LAM should conform to manufacturer specifications and be in line with the job specifications. Proper curing time should also be observed before subjecting it to full water immersion or other forms of exposure.

Maintenance and Repair of Polyurethane Waterproofing Systems

Inspection procedures

Proper inspection procedures are crucial to maintaining the effectiveness of any waterproofing system. For polyurethane waterproofing systems, inspections should be conducted regularly to ensure that there are no cracks, leaks, or other damage. Inspections should be scheduled at regular intervals, such as once a year, and after any major weather event or construction work. During inspections, all areas of the waterproofing should be inspected for signs of damage or wear. The inspection should include a visual examination of the surface for bubbles, cracks or blisters which indicate poor adhesion. A moisture meter can also be used to detect moisture under the membrane before it becomes visible. In addition to inspecting the polyurethane membrane itself, it is important to examine all penetrations in the system like pipes and drains that penetrate through it since they can cause leaks if not correctly sealed.

Repair techniques

In cases where damage has been detected during an inspection or there is evidence that a leak may have occurred, repairs must be carried out immediately. The type and extent of repairs required will depend on the degree of damage.
For small areas with visible bubbles or blisters on Liquid Applied Membrane (LAM), an incision can be made with a utility knife to release trapped air; then it’s sealed again with more LAM applied over it.
For larger damaged areas (e.g., punctures), applying a patch is necessary which involves cleaning out the damaged areas first before applying patching material over them.
Preformed membranes can also be repaired by using patches for damage caused by punctures and their edges must then be sealed off properly with adhesive tapes. For both LAMs and preformed membranes, using sealants like liquid silicones is an effective solution for repairing gaps between existing membranes and newly installed penetrations.
In addition, it is important to ensure that proper surface preparation is carried out before any repair work is done to ensure the new material adheres correctly. Proper maintenance and repair of polyurethane waterproofing systems are crucial for keeping the building safe from water damage.
Regular inspections can help detect problems early on and prevent more significant issues down the line. When repairs are necessary, it is essential that they are carried out quickly and with appropriate techniques to prevent further harm.
By following these guidelines, property owners can protect their buildings from water infiltration and avoid costly damage down the road.

FAQ about Polyurethane Waterproofing

If you’re considering polyurethane waterproofing for your project, you may have some questions about its benefits, applications, and installation process. In this FAQ, we’ll answer some of the most frequent questions about polyurethane waterproofing.

What is polyurethane waterproofing?

Polyurethane waterproofing is a type of waterproofing that uses a liquid membrane made of polyurethane. This membrane is applied to the surface to create a barrier that prevents water from penetrating.

What are the benefits of polyurethane waterproofing?

Polyurethane waterproofing has many benefits, including:

  • Durable and long-lasting protection against water damage
  • Flexible, so it can withstand movements and vibrations without cracking
  • Seamless application, which reduces the risk of leaks
  • Easy to apply and maintain
  • Can be used on various surfaces, including concrete, metal, and wood

Where can polyurethane waterproofing be used?

Polyurethane waterproofing can be used in various applications, including:

  • Roof waterproofing
  • Basement waterproofing
  • Balcony waterproofing
  • Bridge and tunnel waterproofing
  • Swimming pool waterproofing
  • Waterproofing of water tanks and reservoirs

What is the installation process for polyurethane waterproofing?

The installation process for polyurethane waterproofing typically involves the following steps:

  1. Surface preparation: The surface must be cleaned and free of any debris, oil, or grease.
  2. Priming: A primer is applied to the surface to enhance the adhesion of the membrane.
  3. Membrane application: The polyurethane membrane is applied to the surface using a spray, roller, or brush.
  4. Curing: The membrane is left to cure for a specific period, depending on the manufacturer’s instructions.
  5. Inspection: The surface is inspected for any defects, and additional layers may be added if necessary.

Is polyurethane waterproofing environmentally friendly?

Polyurethane waterproofing can be eco-friendly, depending on the type of polyurethane used. Some manufacturers offer low-VOC (volatile organic compounds) and solvent-free polyurethane membranes, which are more environmentally friendly.

How long does polyurethane waterproofing last?

Polyurethane waterproofing can last for 10-20 years, depending on the quality of the membrane and the installation process. Proper maintenance, including regular cleaning and inspection, can also extend the lifespan of the membrane.

How much does polyurethane waterproofing cost?

The cost of polyurethane waterproofing depends on several factors, including the surface area, the number of layers needed, and the location of the project. It’s best to get a quote from a professional waterproofing contractor for an accurate cost estimate.


Summary of Key Points

Polyurethane waterproofing is a highly effective method of preventing water damage in a range of construction applications. Two primary types of polyurethane waterproofing exist liquid applied membrane (LAM) and preformed membrane. LAM is applied via a multi-step process involving surface preparation, priming, and multiple coats of material, while preformed membrane involves the installation of ready-made sheets to protect surfaces from water penetration.
The advantages of polyurethane waterproofing include its durability, flexibility, chemical resistance, and UV resistance. However, there are some potential drawbacks to consider as well. Polyurethane waterproofing can be costly to apply, and it requires skilled labour to ensure proper installation. Proper maintenance and repair are crucial for ensuring long-lasting protection against water damage. Inspection procedures should be carried out regularly to identify any existing issues or potential problem areas.
Repair techniques may involve re-sealing joints or cracks with new polyurethane sealant materials.

Future Developments in Polyurethane Waterproofing

As technology continues to advance in the construction industry, so too will options for polyurethane waterproofing improve. One development that has already occurred is the introduction of hybrid coatings consisting of both polyurea and polyurethane components.
These hybrid coatings offer greater versatility in application methods and cure time while retaining many benefits associated with traditional polyurethane coatings.
Another area where future developments may occur is in the production of more environmentally friendly materials used for polyurethane waterproofing systems. Some manufacturers have already begun exploring eco-friendly options including using recycled materials or reducing the amount of VOCs (volatile organic compounds) emitted during application.
Advancements in nanotechnology may lead to new breakthroughs in the creation of self-healing membranes that can automatically repair small cracks or gaps caused by wear and tear over time.
As the industry advances further into the future, it is certain that new innovations in polyurethane waterproofing will continue to emerge.