Waterproofing of a flat roof

What is flat roof waterproofing?

Waterproofing a flat roof means protecting the roof surface against the penetration of water and moisture. This is a key element in the construction and maintenance of the longevity of the roof, especially in the case of flat structures that are more susceptible to water accumulation. In the past, bituminous membranes such as felt felt were used as the basic roof protection against moisture. Over the years, however, they degrade significantly, and new methods of securing flat roofs are being sought. Such methods include the application of liquid roofing membranes , such as , acrylic 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 capabilities. Water often retains on their surface, which can lead to:

• Moisture penetration into the building,
• Mold and fungi formation,
• Structural damage caused by long-term exposure to moisture.

Additionally, UV rays contribute to the formation of the above-mentioned structural damage. Selecting a waterproofing system is therefore very important to keep 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,
• Reducing the durability of building materials,
• Increased operating costs related to repairs and renovations.
• High temperature in attic rooms.

Types of waterproofing for flat roofs

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 the years, it is easily damaged and often cracks, which causes leaks. Bituminous coatings are black in color, which additionally absorbs heat, heating up and leading to high temperatures in rooms located on the top floors of residential buildings. Most often, roofing felt laid many years ago is protected with polyurethane , acrylic or polyurea .

Polyurethane coatings

Polyurethane coatings are a modern solution that create a uniform, seamless layer. They are perfect for roofs with irregular shapes. Thanks to their one-component structure, they are easy to apply - all you need to do is mix the liquid polyurethane membrane in the packaging and then apply it with a roller, brush or spray. Polyurethane membranes such as Neoproof® PU W-40 or Neoproof® PU Fast -30 are water-based, which reduces unpleasant odors and is also environmentally friendly.

Polyurea coatings

The most durable method of waterproofing a flat roof, which demonstrates not only excellent resistance to moisture, but also enormous flexibility of the material, up to 400%. This translates into almost impossible to break the coating, apart from intentional mechanical damage. Neoproof® Polyurea R , which represents this type of coating, is a material that ensures waterproofing of a flat roof for several to over 25 years. The two-component structure of the product translates into durability, but also mechanical and chemical resistance of the hardened coating. The product is also resistant to early rainfall, so it can be applied in uncertain weather without fear of the material flowing from the roof.

Acrylic coatings

This type of membrane is very similar to polyurethane membranes, because chemically these groups are very similar to each other. Neoroof, i.e. a hydrated acrylic membrane, is an ideal solution for, among others: flat roofs protected with PUR foam or sheet metal. Thanks to the low consumption of these materials, you can cost-effectively protect your flat roof against moisture. It is also worth noting that this membrane is hardened under the influence of UV rays. Therefore, not only is it resistant to them, but they are also necessary in the process of hardening of the coating.

Advantages of waterproofing a flat roof

• Protection against leaks : Effective barrier against water and moisture. Seamless construction, as well as the possibility of strengthening the entire surface or joints with a special reinforcing non-woven fabric, e.g. Neotextile . Thanks to this, the roof is protected for at least a dozen or so years, without fear of leaks.
• Improving energy efficiency : Appropriate insulation can reduce heat loss. The use of white roofing membranes such as Neoproof® Polyurea R , Neoproof® PU FAST or Neoproof® PU W -40 allows you to obtain the so-called "cool roof" effect. White coatings not only reflect light rays, lowering the temperature of the roof surface, but also lower the temperature of the rooms located directly under the roof. The described reflection of light rays also increases the efficiency of photovoltaic panels.
• Increased roof life : Protects the structure from moisture damage. Properly performed waterproofing significantly extends the life of the roof, but also of the entire building. Therefore, it is worth choosing modern waterproofing methods that are light materials and do not burden the building structure. This is an undoubted advantage over traditional roofing felt.
• Reduced maintenance costs : Long-lasting protection reduces the need for frequent repairs. However, if they appear due to mechanical damage or simply over time, repairs can be easily made, at least locally, by applying an additional layer of coatings.

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 used to protect the roof and identify any damage.

Removal of impurities

The roof surface should be cleaned of dust, debris and other contaminants to ensure good adhesion of waterproofing materials. It is also important to degrease the surface, because greasy contamination comes from, among others, from exhaust gases settle on the roof and significantly reduce the adhesion of all materials. You can use Sulfanol . It is worth remembering to remove fungi from the roof surface if fungus appears on it. Washing alone may not be sufficient due to the retention of mycelium in the pores of, for example, roofing felt. At the earliest opportunity and favorable conditions, the fungus will reappear. Therefore, it is recommended to use a special agent that will remove existing and visible mold, as well as protect the roof against its development in the future.

Damage repair

Any cracks, holes or irregularities must be repaired before applying the waterproofing. If there are visible blisters on the felt, moisture is probably accumulating underneath them. They should then be cut and the gaps filled using Jointex® in the case of water-based waterproofing membranes or Neotex® PU Joint if solvent-based membranes such as Neoproof® Polyurea R .

Choosing the right materials

The selection of technology and materials depends on the type of roof, its purpose and the investor's budget. The minimum durability of the coating and its subsequent renovation and maintenance should also be taken into account.

How to waterproof a flat roof?

Substrate preparation

The substrate should be dry, clean and free of loose fragments. They should be properly washed, preferably with a pressure washer, removed from mold and degreased. This will allow you to create adequate adhesion for the primer.

Application of the priming layer

A primer should be spread on the roof surface to increase the adhesion of the waterproofing. In the case of 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. In the case of substrates such as EPDM membranes, PVC, sheet metal, aluminum or concrete, it is necessary to select an appropriate primer.

Membrane installation or coating application

Depending on the selected system, the membrane is applied using a roller, brush or mechanical spray. The work begins with securing the joints between the sheets of the old waterproofing coating, chimney outlets, flashings and all connections between the verticals and the horizontal. Only in the next step 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 keep your roof in good condition. Recommended:

• Periodic cleaning of surfaces,
• Inspection of the condition of membranes or coatings,
• Repair of minor damage as soon as it is detected.