The durability of roofing and underground building structures directly depends on the proper calculation and selection of the components of the insulation layer. Modern torch-applied bituminous waterproofing is a multilayer composite material in which a modified bitumen-polymer binder ensures complete waterproofing, while the inner load-bearing base of the roll waterproofing membrane absorbs all external mechanical loads.
The proper selection of a reinforcing framework—whether polyester, glass fiber mat, or glass fiber fabric—determines how the waterproofing membrane will behave under natural foundation settlement, cyclic expansion of temperature joints, and constant operational deformations of the entire building.
Mechanical Behavior of Reinforcing Frames Under Static and Dynamic Loads
Different types of internal frames respond fundamentally differently to tension, shear, bending, and temperature fluctuations in the load-bearing structures.
Nonwoven polyester: ultimate elongation and crack resistance
Polyester fabric is formed from randomly oriented synthetic fibers bonded thermally.
- The elongation at break of polyester ranges from 30% to 50%.
- The material functions like an elastic spring: when cracks open in a concrete slab, the membrane stretches smoothly without breaking the continuous bitumen layer.
- This is a reliable option for structures subject to high dynamic, vibration, and wind loads.
Glass fiber mesh: high dimensional stability at low tensile loads
Glass fiber mesh consists of short, randomly distributed chopped glass fibers.
- It has minimal elongation at break—no more than 1.5–2%.
- It ensures ideal dimensional stability of the sheet during installation: the roll does not shrink or deform when exposed to a torch flame.
- It has low tensile strength, so it is used on stable, non-deformable structures or as a bottom backing layer in two-layer systems.
Woven fiberglass (fiberglass fabric): ultimate tensile strength
Fiberglass fabric is manufactured using a traditional textile weaving process involving strong glass fibers.
- The main technical advantage is the high tensile strength of the bitumen membrane (from 800 to 1,000 N/50 mm and higher).
- The relative elongation coefficient remains low—within 2–3%.
- The reinforcement structure withstands constant static pressure exceptionally well and protects the membrane from punctures and through-penetration mechanical damage.
The Dangers of Using Inelastic Substrates on Deformable Foundations
A common mistake in the design of insulation systems is selecting a material based solely on its high tensile strength, without taking into account the elasticity and mobility of the foundation itself.
If monolithic reinforced concrete, precast slabs, or profiled metal sheets settle or expand due to heat, microcracks will inevitably form in the structure. Membranes made of glass mat or glass fabric are unable to stretch along with the substrate due to the rigidity of the glass fibers. As a result, the membrane tears instantly, leading to a complete loss of watertightness.
In answering the practical question “glass-fiber mat or polyester: which is better?”, design practice provides a clear guideline: only elastic polyester is suitable for structures that are subject to movement, vibration, and shrinkage. Glass-fiber-reinforced substrates are economically and technically justified exclusively on rigid, stable screeds and precast substrates without the risk of deformation.
Selection Matrix for the TM and Orko Series Based on Specific Building Structures
To accurately match material characteristics with the requirements of project documentation, the TM and Orko product lines are categorized by structure type as follows:
| Structure Type | Recommended Series | Reinforcing Base | Notes |
|---|---|---|---|
| Trafficable flat roofs and top layers | TM Membrane | Nonwoven polyester | With protective slate coating |
| Standard stable roofs | Orko | Glass fabric or glass mat | Without slate coating |
| Deep foundations and stylobates | TM Foundation | Reinforced polyester | For groundwater pressure |
| Lower underlayment layers | Orko | Glass cloth or glass fiber mat | First layer of two-layer system |
| Inter-floor slabs and floors | TM / Orko | Depending on rigidity | Non-grained version |
Explore the recommended products for each application below:
TM Waterproofing Membrane 4mm – Polyester Carrier (APP Polymer)
Manufactured from modified bitumen with APP (Atactic Polypropylene) ad...
TM Waterproofing Membrane 3mm – Polyester Carrier (APP Polymer)
Manufactured from modified bitumen with APP (Atactic Polypropylene) ad...
Orko Waterproofing Membrane 3mm – Fiberglass Carrier (APP Polymer)
Manufactured from modified bitumen with APP (Atactic Polypropylene) ad...
Orko Waterproofing Membrane 4mm – Fiberglass Carrier (APP Polymer)
Manufactured from modified bitumen with APP (Atactic Polypropylene) ad...
Conclusion
Choosing the right reinforcing substrate involves striking a balance between strength, flexibility, and the project budget. Nonwoven polyester ensures resistance to structural movement, fiberglass mesh protects against puncture, and fiberglass fabric provides dimensional stability and affordability. A comprehensive approach to selecting products from the TM and Orko lines allows you to create a reliable waterproofing system with a design life of 15 to 30 years without the risk of emergency leaks.