Roof waterproofing and insulation – Materials and applications

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Waterproofing is the process of coating surfaces in buildings or other structures with suitable materials to prevent water penetration. Its main purpose is to keep water out of structures such as roofs, roof terraces, walls and basements.

Effective waterproofing is essential because water ingress can cause numerous problems within a building or throughout an entire building complex.

Waterproofing materials and application requirements

Two main categories of materials are used for waterproofing roofs and roof terraces:

A) Liquid-applied materials, such as elastomeric acrylic coatings, bituminous coatings, polyurethane products and cementitious slurries.

B) Waterproofing membranes, such as bituminous membranes, glass-fibre fabrics, PVC, EPDM and HDPE membranes, self-adhesive membranes and joint-sealing tapes.

During the construction of most buildings, specialist waterproofing is not usually given sufficient consideration, except in certain specialised structures. Over time, however, deterioration such as cracks in terrazzo roof surfaces or cracked render creates an urgent need to waterproof various surfaces.

The following factors should be considered when selecting the appropriate material:

  • the climatic conditions of the area,
  • the type and material of the surface,
  • and the available application budget.

Application materials

  • Liquid-applied elastomeric waterproofing coating for roofs and roof terraces
  • Primer for liquid-applied elastomeric waterproofing coatings
  • Fibreglass mesh
  • Polyester reinforcement fabric for waterproofing coatings

Tools

  • Spatula
  • Brush
  • Paintbrush
  • Roller with extension pole

Purpose and requirements

Waterproofing systems for roofs and roof terraces must provide watertightness, reliability, long-term durability, flexibility and strong adhesion, regardless of weather conditions.

Most liquid-applied elastomeric products meet these requirements by forming a continuous, flexible membrane without joints or seams. They provide effective adhesion, flexibility and resistance to UV radiation and weathering, while offering an easy and cost-effective solution—even for difficult-to-waterproof areas.

Roof and roof terrace waterproofing application

Complete waterproofing of a roof surface

  1. Thoroughly clean the surface, ensuring it is dry and free from loose material, dust and grease.
  2. Apply a suitable primer to create the correct substrate for the waterproofing material.
  3. Once the primer has dried (1–2 hours), apply the elastomeric waterproofing coating by brush or roller in two coats. Apply the second coat crosswise after the first coat has dried.
  4. Where cracks are present on the roof surface, locally reinforce the elastomeric membrane using polyester fabric or glass-fibre mesh tape.
  5. Once the reinforced areas have dried, apply one or two additional coats of the elastomeric waterproofing material over the entire surface.
  6. Extend the waterproofing coating onto all vertical and perimeter surfaces, such as parapets and upstands, to a height of approximately 10–15 cm, creating a fully sealed waterproof enclosure.

Local sealing of cracks

  1. Thoroughly clean the crack and remove all dust, loose material and grease.
  2. Apply primer along the crack over an area approximately 10 cm wide.
  3. Once the primer has dried, apply the elastomeric material and embed glass-fibre mesh or polyester fabric while it is still wet.
  4. Once the first coat has dried, apply one or two final coats of the elastomeric material.

Useful waterproofing and maintenance tips

Waterproofing work on the roofs or roof terraces of existing buildings can even be carried out as a DIY project, provided the surface is properly prepared beforehand.

Do not carry out waterproofing work when conditions are cloudy, humidity levels are high or rain is forecast. The ideal period for these applications is from May to September.

Pay particular attention to areas where standing water tends to collect. In these locations, the waterproofing system should be reinforced with polyester fabric or glass-fibre mesh tape.

The use of higher-performance elastomeric materials is also recommended for improved resistance and durability.