Flat roof waterproofing

What is flat roof waterproofing?

Flat roof waterproofing protects the roof surface from water and moisture infiltration. This is a key element in roof construction and longevity, especially in flat structures, which are more susceptible to water accumulation. Bituminous membranes, such as felt, were once used as the primary roof protection against moisture. However, over the years, these membranes have degraded significantly, and new methods for protecting flat roofs are being sought. These methods include the application of liquid roofing membranes , such as polyurethane coatings , acrylic coatings , or polyurea coatings (often called liquid rubber ).

Why does a flat roof require waterproofing?

Flat roofs, due to their low slope, have limited rainwater drainage capacity. Water often stagnates on their surface, which can lead to:

• Moisture penetration into the building,
• Formation of molds and fungi,
• Structural damage caused by prolonged exposure to moisture.

Additionally, UV rays contribute to the structural damage mentioned above. Choosing the right waterproofing system is therefore crucial to keeping the roof and the entire building in good condition for as long as possible.

What are the consequences of lack of waterproofing?

Lack of proper waterproofing can result in serious problems such as:

• Flooding of rooms under the roof,
• Decreased durability of building materials,
• Increased operating costs related to repairs and renovations.
• High temperature in attic rooms.

Types of flat roof waterproofing

Bituminous waterproofing

Bitumen is a traditional waterproofing material that can be used in the form of heat-sealable felt or bituminous masses. It is durable but requires careful application. Over time, it is easily damaged and often cracks, leading to leaks. Bituminous coatings are black, which additionally absorbs heat, heating up and leading to high temperatures in rooms on the top floors of residential buildings. Typically, previously installed felt is protected with polyurethane , acrylic , or polyurea coatings .

Polyurethane coatings

Polyurethane coatings are a modern solution that create a uniform, seamless layer. They are ideal for roofs with irregular shapes. Their single-component construction makes them easy to apply. Simply mix the liquid polyurethane membrane in the package and then apply it with a roller, brush, or spray. Polyurethane membranes such as Neoproof® PU W-40 and Neoproof® PU Fast-30 are water-based, which reduces odor and is also environmentally friendly.

Polyurea coatings

The most durable method of flat roof waterproofing, it demonstrates not only excellent moisture resistance but also enormous material elasticity, up to 400%. This translates into virtually impossible damage to the coating, except through deliberate mechanical damage. Neoproof® Polyurea R , which represents this type of coating, provides flat roof waterproofing for a dozen or even more years. The product's two-component construction translates into durability, as well as mechanical and chemical resistance of the cured coating. The product is also resistant to early rainfall, allowing it to be applied in unpredictable weather conditions without fear of the material running off the roof.

Acrylic coatings

This type of membrane is very similar to polyurethane membranes, as these two groups are chemically very similar. Neoroof, a hybrid acrylic membrane , is an ideal solution for flat roofs protected with PUR foam or sheet metal, among other things. Thanks to the low consumption of these materials, you can protect flat roofs from moisture at a low cost. It's also worth noting that this membrane is UV-cured. Therefore, it is not only resistant to UV rays but also essential for the coating's curing process.

Advantages of flat roof waterproofing

• Leak protection : An effective barrier against water and moisture. Seamless construction, along with the ability to reinforce the entire surface or joints with a special reinforcing fabric, such as Neotextile , ensures your roof is protected for at least a decade without the risk of leaks.
• Improving energy efficiency : Proper insulation can reduce heat loss. Using white roofing membranes such as Neoproof® Polyurea R , Neoproof® PU FAST , or Neoproof® PU W -40 allows for the so-called "cool roof" effect. White coatings not only reflect light rays, lowering the roof surface temperature, but also lower the temperature of the rooms directly beneath the roof. This light reflection also increases the efficiency of photovoltaic panels.
• Increasing the roof's lifespan : Protects the structure from moisture-related damage. Properly installed waterproofing significantly extends the lifespan of the roof, and the entire building. Therefore, it's worth choosing modern waterproofing methods, which are lightweight and do not burden the building structure. This is a definite advantage over traditional roofing felt.
• Reduced maintenance costs : Long-lasting protection reduces the need for frequent repairs. However, if such repairs occur due to mechanical damage or simply the passage of time, they can be easily repaired, even locally, by applying an additional layer of coating.

How to prepare a flat roof for waterproofing?

Assessment of the technical condition of the roof

Before starting work, check the condition of the roof surface, the material with which the roof was previously protected, and identify any damage.

Removal of impurities

The roof surface should be free of dust, debris, and other contaminants to ensure good adhesion of waterproofing materials. Degreasing the surface is also important, as greasy contaminants, such as those from exhaust fumes, settle on the roof and significantly reduce the adhesion of all materials. Sulfanol . It's also worth remembering to treat the roof surface if mold has appeared. Washing alone may not be sufficient because the mycelium is trapped in the pores of roofing felt, for example. The mold will reappear at the next opportunity and under favorable conditions. Therefore, it is recommended to use a special agent that will remove existing and visible mold and protect the roof from future growth.

Repairing damage

Any cracks, holes, or irregularities must be repaired before applying the waterproofing. If blisters are visible on the felt, moisture is likely trapped beneath them. These should be slit open and the gaps filled with Jointex® for water-based waterproofing membranes or Neotex® PU Joint for solvent-based membranes such as Neoproof® Polyurea R.

Choosing the right materials

The choice of technology and materials depends on the roof type, its intended use, and the investor's budget. The minimum durability of the coating and its subsequent renovation and maintenance should also be considered.

How to waterproof a flat roof?

Preparation of the substrate

The substrate should be dry, clean, and free of loose particles. It should be properly washed, preferably with a pressure washer, and degreased and fungicide-free. This will ensure proper adhesion for the primer.

Application of the primer layer

A primer should be applied to the roof surface to enhance the waterproofing's adhesion. For roofing felt and water-based coatings, the recommended primer is Revinex® , which also works well on concrete substrates. Neoproof® Polyurea R can be applied to roofing felt without any primer, after cleaning and degreasing the existing coating. For substrates such as EPDM or PVC membranes, sheet metal, aluminum, or concrete, it is necessary to select an appropriate primer.

Membrane installation or coating application

Depending on the chosen system, the membrane is applied using a roller, brush, or mechanical spray. Work begins by securing the joints between the old waterproofing membrane, chimney outlets, flashings, and all vertical-to-horizontal joints. Only then is the membrane applied to the entire prepared flat roof surface.

Quality control

After completing the work, a leak test should be carried out, e.g. by flooding the roof with water.

Care and maintenance of flat roof waterproofing

Regular inspections and maintenance will keep your roof in good condition. We recommend:

• Periodic cleaning of surfaces,
• Checking the condition of membranes or coatings,
• Repair minor damage immediately upon detection.