Mistakes When Sealing a Balcony or Terrace with Two-Component Flexible Slurry

Balconies and terraces require special protection against adverse weather conditions, which can lead to significant structural damage. A commonly used solution is the application of a two-component flexible slurry for sealing. However, mistakes during this process can result in leaks and further damage. This article highlights the most common causes of balcony damage and key factors for effective waterproofing, ensuring these critical building elements are adequately protected from nature's destructive forces.

Mistakes When Sealing a Balcony or Terrace with Two-Component Flexible Slurry – In This Article You Will Learn:

In This Article You Will Learn:

• • • The Most Common Causes of Balcony Damage
    • Mistakes in Sealing a Balcony or Terrace with Two-Component Flexible Slurry
    • What to Focus On When Waterproofing a Balcony or Terrace
    • How to Waterproof a Balcony Using Flexible Mineral Slurries

We often don’t realize how crucial proper sealing and protection of a terrace or balcony is until we encounter the first problems. Changing weather conditions can adversely affect the structural elements of a building. There are many methods for insulating balconies and terraces, one of which is using a two-component flexible slurry for sealing.

The Most Common Causes of Balcony Damage

Balcony damage is often caused by adverse weather conditions such as rain, snow, and sudden temperature changes. These factors negatively affect the finishing layer and the structure of the balcony slab, especially if there is inadequate waterproofing or poorly sealed parapets. Additionally, the hygroscopic nature of the materials used in the construction of a balcony or terrace—their ability to absorb moisture from the air or ground—plays a significant role. It's also important to note that materials with a porous structure can draw water through capillary action, contributing to the development of damage.

What to Focus On When Waterproofing a Balcony or Terrace

Two-component flexible slurries are among the most popular materials for waterproofing balconies and terraces. They are particularly effective for surfaces with irregular shapes, as they fill all uneven areas seamlessly. However, special attention must be paid to details that are critical to ensuring effective waterproofing. Key areas to focus on include:

• • • • The junction between the wall and the floor
      • Handrail transitions
      • Connections between waterproofing materials and metal flashings
      • Expansion joints
      • Connections with drainage outlets
      • Ensuring a uniform thickness of the waterproofing layer across the entire surface of the terrace or balcony.

How to Waterproof a Balcony Using Flexible Mineral Slurries

• Surface Preparation for the Balcony/Terrace Plate
  Ensure the surface is even, crack-free, stable, and clean.
• Application of Balcony/Terrace Plate Waterproofing
  Use sealing slurries such as Flex Schlämme K11 | Bostik, Kerakoll Aquastop Flex, Schomburg Aquafin 2K/M Plus, Koester NB Elastik Grey, or Mapei Mapelastic.
  Extend the waterproofing layer: approximately 30 cm up the wall for unfinished facades or at least the thickness of the screed slope for finished facades.
• Thermal Insulation Installation
  Lay the insulation layer as needed.
• Slope Layer Construction
  Apply a screed layer (e.g., Baumit Solido 225 or Baumit Solido 160) on the balcony/terrace plate.
  Create indentations along the edges of the screed to accommodate drip profiles.
• Preparation of the Wall Element Surface
  Smooth the wall surface for extending the waterproofing using a cement mortar like BOSTIK Sperrmortel Fein or Baumit UniContact adhesive and skim coat.

• • • Note: A minimum extension of 10 cm is required, but Sanier recommends at least 15 cm.
  • Preliminary Placement of Drip Profiles
    Temporarily place the drip profiles to mark fixing points.
  • Installation of Drip Profiles
    Start installing drip profiles at the corners. Secure them using flexible polyurethane sealant or sealing mortar. Account for the thickness of the sealant when preparing indentations. Tighten the screws of the mounting dowels in the drip profiles.
  • Application of Flexible Slurry Layers
    Use products like Schomburg Aquafin 2K/M Plus, Koester NB Elastik Grey, or Mapei Mapelastic.
  • Accessories
    • Use appropriate accessories tailored to the waterproofing system, such as:
      • Butyl Tape, or
      • Fleece-Laminated Tape with Quartz Primer (e.g., BOSTIK A936).
    • Ensure the decorative plinth elements are sealed properly. If plastering the balcony plinth, seal the junction between the plaster and flashings.
    • For decorative plinth elements, Sanier recommends profiles such as RENOPLAST Pressure Strip C1 + C2.

This process ensures effective waterproofing of balconies and terraces, protecting them from water and weather-related damage for years to come.