Waterproof Membranes
Waterproof membranes block rain and wind while allowing sweat vapour to escape.
Membranes such as GORE-TEX and Pertex use microscopic pores that are small enough to stop liquid water, yet large enough to let moisture vapour pass through. This balance keeps you dry from the outside while preventing sweat from building up inside the jacket.
Why it matters for climbing: Climbing often involves short bursts of high effort followed by static belays. Without a breathable membrane, sweat builds up quickly, leaving you damp — and potentially cold — when you stop moving in exposed positions.
Two-Layer vs Three-Layer Construction
Layer count describes how the waterproof membrane is built into the jacket fabric.
Two-layer jackets bond the membrane to the outer fabric and use a loose lining for comfort. They're typically lighter and more packable, making them a good choice for occasional climbs or as an emergency shell.
Three-layer jackets sandwich the membrane between the outer fabric and an inner scrim, creating a tougher, more stable construction.
Why it matters for climbing:
Two-layer jackets prioritise low weight and pack size. Three-layer jackets are more durable, breathe more consistently under harness pressure, and stand up better to rock, rope, and repeated use on long or technical routes.
Hydrostatic Head (Waterproof Rating)
Hydrostatic head measures how waterproof a fabric is.
Measured in millimetres (mm), this rating shows how much water pressure a fabric can withstand before leaking. For example, a 20,000mm rating means the fabric can resist a 20-metre column of water.
For climbers: 15,000–20,000mm is suitable for most UK climbing. For alpine routes, winter climbing, or prolonged exposure in heavy weather, 20,000mm or higher offers greater reassurance.
RET (Breathability Rating)
RET indicates how easily heat and sweat vapour escape through a jacket.
RET stands for Resistance to Evaporative Heat Transfer. Lower numbers mean better breathability and more efficient moisture management during physical activity.
For climbing: RET 0–6 is ideal for technical climbing and high-output leads. 7–12 works well for general mountaineering. Above 20 suits slower-paced or very cold conditions where heat retention matters more than ventilation.
Packability & Weight
Packability describes how small and light a jacket is when carried in your pack.
Climbers often carry a waterproof "just in case," so weight and pack size matter. Lighter jackets pack down smaller but usually sacrifice durability and features.
General guide: Around 300–500g suits most climbing use. Lighter shells suit fast-and-light ascents, while heavier jackets offer better abrasion resistance and protection for harsher conditions.
PFC-Free DWR
DWR helps rain and snow bead and roll off the outer fabric.
Modern climbing jackets increasingly use PFC-free DWR coatings, delivering effective water repellency without the long-term environmental harm linked to older treatments.
Good to know: If a jacket wets out, it usually means the DWR needs cleaning and reproofing — not that the membrane has failed.
2026 update
Lower-impact membranes & modern laminates
For 2026, many climbing waterproof jackets are shifting toward lower-impact membrane systems, including PFAS-free laminates and recycled face fabrics.
These materials aim to reduce environmental impact while maintaining the durability, weather protection, and breathability required for real climbing use.