What is a liquid membrane and how does it work in roof waterproofing?

What exactly is a liquid membrane and what properties does it have?

Liquid membrane is a modern, flexible waterproofing material that, once applied, creates a tight coating that protects the roof from water, moisture, and UV radiation. It can be constructed from polyurethane, acrylic, or polyurea resins. It is used as a liquid alternative to felt, foil, and mechanically attached membranes. Its applications are extremely versatile—from flat roofs and pitched roofs to terraces and even hard-to-reach areas. 

What are the main components of a liquid membrane?

Depending on the type, the membrane may contain polyurethane resins (highly flexible and resistant) - Neoproof® PU W -40 and Neoproof® PU Fast -30 , acrylic (water vapor permeable) - Neoroof® , or polyurea (exceptionally durable and flexible) - Neoproof® Polyurea R and Neoproof® Polyurea C1 . Membranes can be water-based, e.g., polyurethane and acrylic, or solvent-based - polyurea membranes. Water-based products are often single-component, while solvent-based products are two-component, meaning they consist of a base and a hardener.

Is a liquid membrane the same as a polyurethane or acrylic coating?

A liquid membrane is a general term for a product applied in liquid form that, after curing, creates a waterproofing layer. Polyurethane, acrylic, and polyurea coatings are specific types. They differ in composition, technical parameters, and application areas. 

What are the advantages and properties of a liquid membrane?

• Creates a uniform, seamless coating, 

• Resistant to UV, standing water and extreme temperatures (both negative and positive), 

• Flexible, crack-bridging, 

• Simple cold application, without fire or the use of specialized equipment, 

• Adheres to various substrates (e.g. roofing felt, concrete, metal).

On which roofs can liquid membrane waterproofing be used?

Liquid membranes are a versatile waterproofing solution that can be used on almost any type of roof. Whether you're planning to protect a new project or renovate an existing roof, this technology offers a wide range of adaptability and works perfectly on both simple and complex roofs. 

Is liquid membrane suitable for waterproofing flat roofs?

Yes, this is one of the most common applications. Its ability to create a tight, seamless coating makes it ideal for low-slope roofs where water can accumulate. All waterproofing membranes offered by TrokenTech have excellent resistance to standing water, confirmed by water absorption tests. 

Can it be used on pitched roofs and roofs with complex shapes?

Of course, application with a brush or roller allows you to cover even hard-to-reach parts of the roof, such as installed photovoltaic installations, ventilation or air conditioning. 

Will the liquid membrane work on old roof coverings: roofing felt, sheet metal, concrete?

After proper surface preparation (cleaning and priming), the membrane bonds well to felt, concrete, metal, and most old coatings. Choosing the right primer is crucial, as it will vary depending on the surface; for example, one primer is used on concrete versus a metal roof. It's also worth remembering that primers may differ depending on the system used—solvent-based or water-based. Therefore, it's always worth checking the technical data sheet of the liquid waterproofing membrane, which lists recommended primers for specific applications, or contacting a technical advisor. 

Is liquid membrane waterproofing suitable for green roofs and terraces?

Yes, polyurea-based liquid membranes, such as Neoproof® Polyurea R, are primarily designed for use underground and under load. They protect against root penetration and mechanical stress. Polyurea liquid membranes are also suitable for waterproofing walkable patios. Polyurethane membranes, with the use of Neotextile® throughout the entire surface, can be used, for example, under tiles on spacers or as a waterproofing layer for composite flooring on a patio.

How to prepare a roof for the application of a liquid membrane?

For effective and durable waterproofing, proper substrate preparation is crucial. The adhesion, flexibility, and tightness of the applied coating depend on the quality of this step. This section describes the necessary steps to take before applying the membrane. 

Proper surface preparation is the foundation of effective insulation. Each step is crucial to the adhesion and durability of the membrane. 

Step 1: Assessment of the subfloor condition

Checking the stability of the structure, cohesion, moisture and the presence of cracks or bulges. 

Step 2: Cleaning and preparing the roof surface

Removing dirt, moss, dust, and old, flaking coatings. Regardless of the roof type, the surface should be washed and degreased every time. This can be done using a pressure washer and Sulfanol A. If lichens and fungi are present, it's worth using GrzyboStop , which not only inhibits existing microorganisms but also blocks their future development.

Step 3: Repairing roof damage and gaps

If there are gaps or damage to the roof surface, it is essential to fill them with flexible sealants that can be covered with liquid waterproofing membranes. Jointex® , an acrylic sealant that works well under waterproof membranes such as Neoproof® PU W -40 , Neoroof® , or Neoproof® PU Fast -30 . The second type is the polyurethane sealant Neotex® PU Joint , which is used to seal and fill gaps under polyurea membranes such as Neoproof® Polyurea R or Neoproof® Polyurea C1 .

Step 4: Priming the roof surface

Depending on the surface and the chosen waterproofing system, you should select the appropriate primer. The most popular primers are: 

For concrete:

• Neopox® Primer WS - for damp concrete, for solvent-based systems
• Revinex - for water systems

To Papa:

• Revinex - diluted with water in a ratio of 1:4, for water systems
• Neopox® Primer BM – for use under solvent-based systems when the roofing felt has no grit or is in poor condition. If the felt is undamaged, polyureas can be applied directly to the prepared substrate.

For metal:

• Neopox® Primer 815 - epoxy, solvent-based anti-corrosion primer for two-component systems on trapezoidal sheet metal, black steel,
• Neotex® Metal Primer - water-based anti-corrosion primer recommended for water-based waterproofing systems,
• Neotex® Inox Primer - water-based adhesive primer for smooth substrates such as galvanized steel or aluminum, for both water-based and solvent-based systems.

See also: Case study - Waterproofing two roofs with an area of 1600 m2 using the Neoproof Polyurea R membrane

How to properly install liquid membrane waterproofing on a roof?

Correct application of a liquid membrane creates a durable, uniform coating that protects the roof from water and weather. Regardless of the product type chosen—acrylic, polyurethane, or polyurea—following the application instructions ensures maximum effectiveness and longevity of the insulation. 

What tools and equipment are needed for application?

Rollers, brushes, mechanical mixers, buckets, and scales are the basic tools needed for applying liquid waterproofing membranes. It's also worth remembering that these products can be applied by spray, which significantly shortens the application process. However, it requires specialized equipment, making this an optional solution. 

How to properly mix and prepare the product?

Thoroughly mixing the contents of the package ensures the proper consistency of the material. For two-component products, such as Neoproof® Polyurea , it is necessary to combine the base (component A) and hardener (component B) in the correct ratio. A scale will be necessary to measure smaller portions.

How many layers of liquid membrane should be applied for optimal protection?

Depending on the substrate and product, two layers are most often applied crosswise, with a consumption of 1.5-2.5 kg/m². There are exceptions, such as PUR foam, where Neoproof® Polyurea C1  can be applied in a single layer, with a consumption of 0.75 kg/m², ensuring the durability of the entire waterproofing system.

What are the optimal weather conditions for application?

Depending on the product, this will be a temperature range from +5°C or 12°C, to +35°C - 40°C, no precipitation for at least one ( Neoproof® PU Fast -30 , Neoproof® Polyurea R ) to even a dozen ( Neoproof® PU W -40 , Neoroof® ) hours, relative humidity below 80%.

How to protect roof details when installing a liquid membrane?

In critical areas, Neotextile® between the first and second layers of the liquid waterproofing membrane. The membrane is applied in such areas using the "wet-on-wet" method.

The most common mistakes when applying a liquid membrane to a roof

Although liquid membrane technology is considered simple and intuitive, in practice, mistakes are easily made that can reduce the insulation's effectiveness. In this section, we describe the most common mistakes made by contractors and DIY enthusiasts, and provide tips on how to avoid them. 

Incorrect preparation of the substrate

A dirty, damp, or unprimed surface reduces adhesion and causes loosening. Improper primer selection can also result in reduced adhesion and, consequently, problems with the curing or durability of the coating. 

Bad weather conditions and rushed application

Application in unfavorable weather conditions can significantly impact the application and curing process. Too low a temperature, too high a humidity, and even rainfall extend the curing process. In unpredictable weather, it's worth choosing solutions that guarantee resistance to early rainfall after just one hour, such as Neoproof® PU Fast -30 or Neoproof® Polyurea R/C1. 

Inappropriate reinforcements

Neotextile® reinforcements on flashings, skylights, downspouts and edges may result in leaks.

How to care for a roof protected with a liquid membrane?

Properly installed liquid membrane waterproofing can last for many years, provided it's regularly maintained and cared for properly. Learn what steps you should take to ensure your roof remains airtight, aesthetically pleasing, and resistant to external factors for a long time. 

Does the liquid membrane require special maintenance?

No, but inspections are recommended at least once a year and after heavy rainfall, hailstorms, or windstorms. Cleaning can extend their lifespan.

What are the possibilities for repair and renovation in the future?

Liquid membranes can be spot-repaired. Simply clean the surface, prime, and apply a fresh coat. You can also apply another layer of membrane to the entire roof to seal it and extend its lifespan. 

How long does a liquid membrane retain its properties?

Depending on the type of product and thickness used: from 10 to even 25 years, with proper maintenance and regular inspections.

What is a liquid membrane and how does it work in roof waterproofing - frequently asked questions

If you're considering using a liquid membrane, you likely have questions about its durability, range of applications, and differences in application compared to other methods. In this section, we answer the most common questions and dispel myths about this type of waterproofing. 

Is the liquid membrane resistant to structural movement and cracking?

Yes, especially polyurea-based products bridge cracks up to 1 mm. 

What are the main differences in liquid membrane application compared to traditional roller methods?

No joints, easier access to hard-to-reach places, faster work pace and no fire. 

Can a liquid membrane be used as the only waterproofing layer or does it require additional protection?

It can be used on its own, if the system requires it. For utility roofs, it may require a protective or finishing layer (e.g., flakes, topcoat resins).