When designing and constructing buildings in regions with extreme climatic conditions (Central Asia, the Middle East), the choice of roofing waterproofing determines the durability of the entire structure. Surface temperatures on flat roofs in these regions regularly reach +80 °C, and intense UV radiation accelerates material degradation.

The main dilemma for designers and construction supervision engineers is whether to specify APP or SBS waterproofing membranes in the project. Let’s examine the physical and chemical differences between these polymers and determine the optimal solution.


Polymer Physics: Elastomers vs. Thermoplastics

The choice of modifier fundamentally changes the behavior of the bituminous binder:

  • SBS (styrene-butadiene-styrene) is a synthetic rubber (elastomer). It gives the material excellent elasticity and flexibility at subzero temperatures (down to -25 °C).
  • APP (atactic polypropylene) is a thermoplastic. It forms a strong, high-melting-point matrix within the bitumen structure, which is critical for performance in extreme heat.


Heat Resistance and Stability on Slopes

The key factor for southern latitudes is the heat resistance of roll-type waterproofing. For SBS materials, this is typically limited to +100 °C. When the roof is heated to +80 °C, SBS bitumen comes dangerously close to its softening point. This creates a risk of the material slipping at vertical joints and the membrane being punctured during roof maintenance.

APP modified bitumen exhibits a fundamentally different level of performance: its softening temperature exceeds +150 °C, and the guaranteed heat resistance of the finished membrane is at least +120 °C... +130 °C. The material retains its stable shape and rigidity even at midday under direct sunlight.


The Problem of Photo-Oxidative Aging

UV radiation is the main enemy of roofing membranes. When exposed to light quanta, a degradation process is triggered in the SBS modifier (due to the presence of carbon double bonds). The rubber loses its elasticity, becomes brittle, and develops microcracks.

The APP modifier (polypropylene) is resistant to photo-oxidative aging. The molecular structure of the thermoplastic does not break down under intense ultraviolet radiation. As a result, APP membranes retain their waterproofing and flexibility 1.5–2 times longer than SBS counterparts in arid and hot climates.


An Expert Solution for Southern Climates

Based on an analysis of physical and mechanical properties, the APP-class waterproofing membrane is the clear favorite for flat roofs in high-temperature environments.

For Mizemez Gadam projects requiring uncompromising reliability, the optimal engineering solution is to use the professional TM Membrane P3000/P4000 line. These hot-applied APP membranes are designed specifically for areas with high solar radiation. The high reinforcement density, combined with a premium APP-modified binder, guarantees a service life of more than 20–25 years between repairs without the risk of deformation or cracking.