Waterproof & Breathability Ratings Explained

On most snowboard outerwear you should see a two number rating (if not, run) the first number is the waterproof, the second is breathability. The higher the rating, the more waterproof, and the more breathable the jacket or garment is. This is typically done in mm or for example you might see 20K/15K - This means 20,000mm waterproof and 15,000mm breathability.

Below is a guide on Waterproofing and how your garment should hold up depending on the conditions.

Waterproof Rating (mm) Water Resistance  Conditions
0-5,000 mm No resistance to some resistance to moisture.  Light rain, dry snow, no pressure.
6,000-10,000 mm Rainproof and waterproof under light pressure. Light rain, average snow, light pressure.
11,000-15,000 mm Rainproof and waterproof except under high pressure. Moderate rain, average snow, light pressure.
16,000-20,000 mm Rainproof and waterproof under high pressure. Heavy rain, wet snow, some pressure. 
20,000 mm+ Rainproof and waterproof under very high pressure. Heavy rain, wet snow, high pressure.


What is Breathability and Why do I Need It?

Breathability is normally expressed in terms of how many grams (g) of water vapor can pass through a square meter (m2) of the fabric from the inside to the outside in a 24 hour period. In the case of a 20k (20,000 g/m2) fabric, this would be 20,000 grams of moisture transfer.

Essentially, you want it where the raindrops can't get in but the evaporated sweat coming off your hard-working body can get out. Getting the size of the holes perfect to maximise both operations is tricky, plus expensive. Generally, the more breathable a fully waterproof membrane is, the more expensive it will be to produce.

What is Seam Sealing and Why Do You Need It?

Seam sealing, sometimes referred to as seam taping, covers the tiny holes made by the needle in the sewing process so they don’t leak. Sometimes seams are bonded together using glue or heat, but typically they are first sewn then taped. Jackets, pants, and other outerwear can be either “fully taped” or “critically taped” – the difference is that a fully taped garment has every seam taped, while a critically taped one has tape only on high exposure areas like the neck, shoulders, and chest. Without adequate seam sealing you’ll get wet even with the best waterproof/breathable fabric.