The membrane's porous network, formed through controlled stretching of EPTFE, must have pores sized to block liquid water while allowing water vapor or gases to pass. Manufacturers tune stretching parameters to create an interconnected pore system with consistent, optimized dimensions.

While EPTFE inherently has low surface energy, targeted treatments can enhance water repellency without blocking pores. Thin, low-surface-energy coatings strengthen the membrane's ability to repel water droplets without narrowing pore channels.

A thinner membrane boosts breathability but risks compromising structural integrity. Layered designs use a thin, highly porous inner layer for breathability and a slightly denser outer layer to reinforce waterproofness.

Manufacturing processes that maintain uniform stretching and avoid over-compression preserve pore connectivity, allowing vapor to move continuously through the membrane while maintaining waterproofness.