Waterproofing

Polyurethane Based Waterproofing: Application method, Advantages and Disadvantages

2 years ago
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by David J
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Written by David J

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Polyurethane consists of two components: a base and a reactor. Polyol acts as a base, and isocyanide acts as a component of the reactor. The combination of both of these factors in a certain constructive ratio creates a liquid layer for waterproofing. Polyurethane is a fairly popular choice for waterproofing works due to its reliability and distinctive qualities, such as the absence of seams, good adhesion to different surfaces, etc. unlike other waterproofing systems, such as sheet and roll waterproofing membranes.

Advantages of polyurethane mastic for waterproofing

Polyurethane products and mastics can be double-component and single-component. Polyurethane waterproofing mastic has a number of notable advantages, including:

  1. Lack of seams – Unlike materials such as PVC membranes or surfaced types of waterproofing (according to the type of rolled materials from Technonicol), polyurethane mastic, when applied, has no seams, and as everyone knows, it is the seams that are the weakest point in any waterproofing system, since during shrinkage of a building, structural dynamics or screed, it is the seams that diverge in the first place.
  2. Coefficient of stretching – Most high-quality polyurethane mastics have a large coefficient of stretching, respectively, they do not crack and do not diverge when the building shrinks or the dynamics of the surface on which they are applied.
  3. Adhesion to the surface – Polyurethane waterproofing in the form of mastic, 100% adhesion to the surface on which they are applied, which means that under the waterproofing layer, there will be no cavities through which water can walk or stagnate. Unlike this type of mastic, membrane and surfaced waterproofing has voids between the waterproofing coating and the base, respectively, water can enter in one place, then walk under the waterproofing carpet and exit inside the building in a completely different place.
  4. The speed of work – most polyurethane compounds and mastics can be applied by spraying, which means that a working unit of 3 people can cover an area of 300-400m2 per day.
  5. Color scheme – Polyurethane compounds and mastics are usually available in different colors, which is important mainly when it comes to waterproofing the roof, open balcony or terrace as the final coating.
  6. Durability and wear resistance. Polyurethane mastics serve for at least 30 years.
  7. Ultraviolet and weather-resistant – Most polyurethane-based waterproofing mastics are UV-resistant, and accordingly can be applied as a finishing layer on the roof, terrace or outdoor balcony.

Polyurethane waterproofing for concrete

Detailed methods of preparation and application of polyurethane compounds to various areas, including concrete, are prescribed by the product supplier and are often controlled by him in large project applications. Waterproofing is an expensive and responsible business, respectively, it is best to entrust it to professionals.

When applying polyurethane based waterproofing on concrete, the following recommendations should be followed:

Preparation of concrete

  1. The outer layer of concrete is thoroughly dust-free and cleaned of any foreign substances. 
  2. Any cracks on the preparatory layer of concrete are stitched to a V-shaped section, cleaned and filled in layers with a special repair compound or expanding sealants of the HydroExpand type.

Applying material to the concrete:

  1. Before applying polyurethane product to the concrete surface, it is necessary to apply a special primer suitable for the selected material.
  2. After applying the primer, polyurethane material or mastic is recommended to be applied to concrete in 2-3 layers, depending on the design. The number of layers can be determined by a professional contractor, having studied the features of the concrete structure. Each layer needs to be dried before applying the next one.

Recommendations:

  • Polyurethane based waterproofing can be applied to concrete, both with a brush and a roller, and mechanized, by spraying the substance on the site. 
  • The polyurethane coating continues 150 mm up the parapets or walls. The approach to all elements, structures and pipes should be at least 100 mm. 
  • Some polyurethane coating, sprinkled with a layer of sand with a volume of 300 microns. 

Waterproofing of a flat roof with a polyurethane liquid membrane

Waterproofing of flat roofs, open terraces and balconies, performed both during the construction of the building and after it, should, in addition to ensuring complete water resistance, exhibit the following characteristics: 

  • Special resistance to atmospheric influences and ultraviolet radiation; 
  • Reliability and durability; 
  • Elasticity; 
  • Good adhesion to the substrate.

For these purposes, in most cases, it is recommended to use imported polyurethane materials, such as PolyFlex from the German company HYDRO or the BASF plant. Today, it is imported materials that have all the necessary qualities for a long service life on the elements of the building, not to mention the fact that most companies involved in waterproofing, including roofs, give them long warranty periods.

Materials and mastics of the PolyFlex type fully satisfy all technical requirements. They demonstrate excellent adhesion to the substrate, flexibility, resistance to weathering, as well as resistance to ultraviolet radiation. The above mentioned materials have good resistance to water pressure, so they can be used on flat roofs without particularly good slopes. They provide a simple, reliable and easy solution for complex sealing points (e.g. corners, edges, joints with roof outlets, etc.).

Polyurethane waterproofing of the roof creates a continuous elastic membrane with excellent mechanical strength, without joints and seams. This composition is used both for complete sealing of flat surfaces and for local waterproofing of cracks.

You can read more about the methods of waterproofing the roof in the following articles:

Single-component polyurethane based waterproofing 

Single-component polyurethane waterproofing is a single-component waterproof polyurethane coating consisting of ingredients such as isocyanates, and polyesters, with some additives.

Characteristics of single-component product:

1. Single unit packing, use up at one time, avoiding low stability to the quality of the waterproof coating. 

2. The feature of the film-forming mechanism, the single-component composition can be used on a dry surface basis. 

3. Single-component mastic made of pure polyurethane, good excellent physical and mechanical properties, excellent flexibility, high intensity with rubber characteristic. 

4. Thick coating, dense coating, no pinhole, no air bubble. 

5. The single-component material goes without benzene solvent, and coal tar components, respectively, the single-component membrane will not pollute the environment. 

Double-component polyurethane based waterproofing

Double-component coating refers to hardening waterproof materials. 

Group A: is an isocyanate pre-finished polymer, polycondensed with polyester and isocyanate. 

Group B: is a colored liquid consisting of a plasticizer, hardener, thickeners, coagulant, and filler. With uniform mixing of groups, A and B in speed and volume on the surface of the waterproofing substrate, an elastic and rubber-like film is formed, which plays the role of waterproofing.

Characteristics of two-component polyurethane based waterproofing: 

1. High elasticity and extensibility. Double-component polyurethane waterproofing has a higher coefficient of tension and elasticity than single-component compositions. 

2. Seamless lining. 

3. Weather resistance, acid-alkali resistance. 

4. UV resistance. 

5. Double-component polyurethane mastic, has strong adhesive properties. 

6. High performance. 

7. Wear resistance. 

8. Harmless to the environment.

Double-component PU waterproofing, suitable for waterproofing: 

  • Balconies; 
  • Terraces; 
  • Roofs; 
  • Swimming pools; 
  • Basements; 
  • Roofs; 
  • Ponds and reservoirs; 
  • Tunnels, bridges, and pedestrian crossings. 

Prices for Polyurethane based waterproofing products 

The price of polyurethane waterproofing depends on the manufacturer, quality, properties, and characteristics. As with most waterproofing materials, the lower the price to buy the material, the less effective and durable it is.

Comparison of prices and characteristics of the world’s most famous products of polyurethane based waterproofing

Name of the materialConsumption per 1m2 per kgPrice per 1kg of material in $Price per 1m2 in $
Basf PCI Apoflex1,6 kg2642
Hydro PolyFlex1,6 kg2439
Mariseal 6002 kg1836
Hyperdesmo2,5 kg1435

The cost calculator for polyurethane liquid membrane application

Where to buy polyurethane based liquid waterproofing and not get caught on counterfeit

It is not so difficult to buy for an ordinary person at an affordable price. You can buy polyurethane waterproofing at an affordable price, mainly from dealers selling manufacturers’ products in a particular region for a certain price. Most dealers offer to buy polyurethane waterproofing, in any volume and for any purpose. You can buy with delivery or pickup from the supplier’s warehouse.

Not all major manufacturers follow the path of retail trade, some factories do not sell their products at retail, respectively, it is quite difficult for an ordinary person to buy them. For example, German company HYDRO sells its products in bulk and in large batches, only to large construction companies that can buy it in large quantities, having their own warehouses and performing waterproofing work in large volumes. 

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