115g, 140g, 165g, 180g…
But the real performance of a membrane is not just about grams per m².
A good breathable underlay should also be assessed by
- tensile strength,
- tear resistance,
- elongation,
- water resistance,
- vapour permeability,
- UV exposure limits,
- and long-term durability.
This is where the technical data matters.
Two membranes can look similar on paper, but perform very differently on site.
Also, declared membrane weight can sometimes be misunderstood. A “165g” membrane is not always about the number alone — the full DOP/TDS should be checked to understand the actual declared performance values and tolerances.
In roofing, numbers are important — but performance is in the full specification, not just the label.
Performance is in the full declaration—not just the label.