These two terms come up regularly when speaking of outdoor clothing or hiking equipment, especially jackets and trousers. Different people can understand the word waterproof differently, which is why we’d like to clarify the terms.

First, a general and simplified definition:

• If a garment is made of waterproof material and all of its seams have been taped, you can call it waterproof.

• If a garment is made of waterproof material, but the seams have only been partially taped or not taped at all, we classify it as water-repellent.

• In addition, products made of a non-waterproof fabric that have been impregnated or treated with a water-repellent finish are classified as water-repellent.

What are waterproof fabrics?

A fabric’s waterproofness can be based either on a waterproof membrane laminated on the underside of the surface fabric or a surface treatment (such as the rubbery finish on traditional raincoats).

Waterproof membranes are often also breathable. This means that the moisture produced by the body can evaporate through the fabric even though liquid water cannot enter through it.
Read more about breathability.

There are differences between the various membranes and finishes, and some of them withstand water better than others. That’s why, in order to find the most suitable clothing for yourself, you should be careful when choosing an outdoor jacket or trousers.

How is waterproofness measured?

A fabric’s waterproofness can be measured with a water column test. In the test, a tube is placed tightly over a fabric, and water is entered into the tube until it begins to seep through the fabric. The height of the water column in the tube indicates how much water pressure the fabric can withstand.

The highest-quality membranes can have a water column rating of up to 28,000 mm – meaning that the measuring tube would have to be 28 metres tall to complete the test in the traditional way! Today, a device similar to a pressure washer can also be used to complete the test. The device simulates the pressure caused by a water column of a certain height.

The higher the water column rating, the better the fabric can withstand water.

What is a good enough water column rating?

In general, a water column rating of 5,000 mm means that the product can withstand normal rain showers in basic use, but if you spend longer times in heavy rain, you should acquire clothing rated between 10,000 and 20,000 mm. GORE-TEX products with a water column rating of 28,000 mm can withstand even the heaviest storms.

The rating you need also depends on how much the fabric will be pressed and stretched. For instance, if you carry a heavy backpack, sit on snow or kneel on wet ground, staying dry requires a higher water column rating because more pressure will be put on the fabric.