Webertherm B-flex
Surface movement, thermal expansion, and cracking risks can significantly affect the performance of exterior wall systems. Webertherm B-flex is a fiber-reinforced, highly flexible, high-performance base coat render specifically developed for gypsum-based exterior sheathing boards and thermal insulation systems.
Its cement-based formula, elastic properties, and fiber reinforcement provide a durable, crack-resistant, and long-lasting surface for exterior applications.
Key Features
- Cement-based and fiber-reinforced formulation
- High crack resistance thanks to its elastic structure
- Excellent adhesion to gypsum-based exterior boards
- Fully compatible with thermal insulation boards
- Resistant to thermal shock
- Suitable for both manual and machine application
These characteristics make Webertherm B-flex an ideal rendering solution for surfaces exposed to movement and thermal stress.
Applications
- Gypsum-based exterior sheathing boards
- EPS insulation boards
- XPS insulation boards
- Mineral wool insulation boards
- Brick and insulated brick surfaces
- Concrete and fair-faced concrete
- Autoclaved aerated concrete (AAC)
- Pumice block and concrete block walls
Suitable as a single-coat base render for both interior and exterior applications.
Surface Preparation
- The substrate must be sound, clean, and dry.
- Boards must be firmly bonded to the substrate.
- Dust, dirt, and loose particles must be completely removed.
Proper surface preparation is essential for achieving optimum adhesion and long-term performance.
Application Procedure
Mixing
- Add 6–6.5 liters of clean water to a 25 kg bag of Webertherm B-flex.
- Mix using a low-speed mixer or trowel until a homogeneous consistency is achieved.
- Allow the mixture to rest for 10 minutes before application.
Application
- Apply the mortar evenly with a steel trowel.
- Embed the reinforcement mesh into the fresh render before it dries.
- The mesh should be installed vertically, kept taut, and free from wrinkles.
- Mesh overlaps should be at least 10 cm.
- Around corners, windows, and door openings, the mesh should wrap a minimum of 20 cm.
Waiting Time Between Coats
- Wait 3–4 hours before applying the second coat.
Consumption
- On thermal insulation boards: approximately 5.0 kg/m²
- On gypsum-based boards: approximately 3.5–4.0 kg/m²
Technical Performance Values
| Property | Value |
|---|
| Compressive Strength | Minimum 6 N/mm² |
| Adhesion Strength to Insulation Boards | ≥ 0.08 N/mm² |
| Adhesion Strength to Gypsum-Based Boards | ≥ 0.5 N/mm² |
| Thermal Conductivity | ≤ 0.45 W/mK |
| Water Vapor Diffusion Resistance Factor | μ ≤ 15 |
Application Conditions
- Ambient temperature: +5°C to +30°C
- Do not apply on frozen surfaces or where frost is expected.
- Avoid application under strong wind, direct sunlight, or excessively hot conditions.
Warnings and Recommendations
- Expansion joints must not be covered; suitable joint profiles should be used.
- Do not apply without reinforcement mesh.
- Reinforcement mesh is mandatory on AAC (aerated concrete) substrates.
Frequently Asked Questions (FAQ)
On which surfaces can Webertherm B-flex be used?
It can be applied to gypsum-based exterior boards, EPS, XPS, mineral wool insulation boards, and various cement-based substrates such as concrete and masonry.
Can it be used as a single-coat render?
Yes. Webertherm B-flex is suitable for single-coat render applications.
Is reinforcement mesh required?
Yes. Reinforcement mesh must be used to minimize cracking risk and ensure system durability.
When can the final decorative coating be applied?
A minimum curing period of 7 days is required before applying the final decorative finish.