Waterproof Guide

Believe it or not, “100% waterproof” fabric doesn’t really exist. With enough pressure, water will pass through anything. This means that all fabrics are technically water-resistant. Synthetic materials like nylon will provide better water-resistance than more absorbent materials like cotton, but untreated fabrics aren’t designed to withstand blasting winds, heavy rain and snow. To be categorized as waterproof, a material must provide a higher level of sustained water resistance. This is accomplished by combining fabric with special waterproof membranes or coatings. When we label a product as waterproof, it must either be made of a waterproof material or include a waterproof breathable membrane (or a waterproof breathable laminate). We do not consider products that only have a DWR (durable water repellent) coating to be waterproof.

Waterproof Rating

A fabric’s waterproof rating is directly related to its ability to withstand water under pressure in a controlled, laboratory setting. In other words, more resistance to pressurized water equates to a higher waterproof rating. Waterproof ratings are measured in two ways:

1. pounds per square inch (psi)
2. mm/24 hours

Common water-resistant fabrics can withstand between 3 to 5 psi of water pressure, which is fine for a brief, light rain shower. A Gore-Tex® shell can withstand about 40 psi of water pressure. This higher rating can become necessary if you’re kneeling on snowpack or carrying a heavy pack in the rain, which puts additional pressure on the fabric.

A "mm/24 hours" rating refers to the amount of rainfall a fabric can withstand in a single day. Thus a 10,000mm waterproof rating means the garment can withstand 10,000mm of rainfall in a single day without letting moisture in. The higher the number, the more waterproof the item will be. Gore-Tex®, for example, has a waterproof rating of 28,000mm.

Sealed, Taped and Welded Seams

Needle-stitched seams create thousands of small holes that allow water to sneak inside, so most high-performance outerwear has sealed or taped seams to prevent leaks. Alternatively, welded seams are bonded using heat and pressure, which does not create any punctures in the material, and therefore won’t compromise the weather protection. In addition to the seams, zippers may either be welded or have storm flaps to prevent water from entering. There are two levels of seam-sealed construction:

1. Critical Seams Sealed: Only the upper body of a garment is sealed or taped. This protects the most vulnerable seams, but leaves lower areas less protected.
2. Fully Seam-Sealed: All seams are sealed or taped for maximum protection in harsh weather.

There are two types of waterproof fabrics:

1. Non-breathable waterproof fabrics are typically used for low-intensity activities in extreme weather conditions. Heavy-duty, PVC-coated rain suits used by commercial fisherman and dock workers are a good example. These garments offer very high weather protection, but don’t allow any internal moisture vapor to escape, which makes them a poor choice for activities like skiing and ice climbing.
2. Waterproof breathable fabric blocks external moisture and also allows sweat vapor to escape, making it appropriate for a wide range of activities. A fabric’s breathability is measured in g/m²/24 hours. This is an expression of how many grams of moisture vapor can pass through a square meter of material in a single day. The higher the rating, the more breathable the fabric.

Waterproof Breathable Membranes

At the heart of most waterproof breathable outerwear is a membrane that contains millions of microscopic "pores" per square inch. These tiny pores can be up to 20,000 times smaller than a water droplet, but are still large enough to allow vapor molecules to pass through. This pore size allows the membrane to be completely waterproof and still allow evaporating sweat to escape. Additionally, an oleophobic (oil-resistant) material is typically integrated into the membrane, preventing the penetration of body oils and other oily substances that can break down the membrane over time.

When a waterproof breathable membrane is laminated to the inside surface of nylon or polyester, it can be used to create waterproof outerwear that is much lighter and less bulky than old-school rain wear. These fabrics are sometimes called laminates. For added protection, most waterproof outerwear is also coated with a durable water repellent (DWR) treatment. This causes moisture to bead up and roll off the surface of the garment, which helps maintain breathability. A few examples of popular waterproof breathable fabrics are Gore-Tex® by W.L. Gore & Associates, HyVent® by The North Face, MemBrain® by Marmot and Omni-Tech® by Columbia Sportswear.

Waterproof Breathability Rating Chart

Below are some examples of several proprietary waterproof breathable fabrics and their different ratings.

For optimal weather protection during activities like hiking, skiing, snowboarding and climbing, waterproof breathable jackets and pants are ideal. Breathability is essential to prevent sweat from building up inside the garment, which makes it harder for you to stay warm. The level of weather protection you’ll need varies depending on the conditions. Below is a set of recommendations for choosing outerwear based on waterproof rating. Be aware that there is no industry standard for waterproofness, and these recommendations are meant to serve as a general guideline only.

• Less than 10,000mm: Minimal protection for activities like running and hiking in intermittent light rain and snow.
• 10,000 - 15,000mm: Medium protection for activities like hiking and skiing in moderate rain, snow and wind.
• 15,000 - 20,000mm: Excellent protection for most activities in moderate rain, snow and wind, with intermittent heavy rain and snow.
• More than 20,000mm: Extreme protection for persistent heavy rain, heavy snow, high winds and very wet environments. Ideal for activities like mountaineering, ice climbing, backcountry skiing and kayaking.

As outerwear has grown more advanced, new fabric technologies have been developed to offer added performance benefits in certain conditions. For example, Gore-Tex® Active Shell and Mountain Hardwear Dry.Q Active offer enhanced breathability for comfort during rigorous activities like skiing and backpacking. Alternatively, Gore-Tex® Pro Shell and Mountain Hardwear Dry.Q Elite provide superior durability and protection in extreme weather conditions. Other proprietary membranes have different advantages, and we do our best to explain these for each product we sell.

Similar to outerwear, waterproof membranes and other barriers can also be built into footwear. Waterproof performance depends on the type of barrier, the materials protecting the barrier and how well you take care of your footwear. For the best protection, look for boots and shoes that include one or more of the following features:

Waterproof Lining

In hiking boots and other footwear, a waterproof breathable membrane like Gore-Tex® is typically bonded to a lining material, which is inserted into the boot to completely surround the foot and prevent moisture from breaching the lining. However, the boot itself can still become saturated with water. To protect the outside of the boot from getting soaked and becoming heavy, a DWR coating or other treatment is usually applied.

Treated Leather

Treated leather, sometimes called “waterproof leather,” is treated with a topical coating to resist moisture, but it’s important to understand that no leather is fully waterproof (despite what some manufactures may claim). High-quality, waterproof leather footwear typically has sealed seams for extra protection, but still isn’t designed to be fully submerged in water for extended periods.

Watertight Construction

Sometimes manufacturers will use terms like watertight construction to designate seam-sealed construction or specialty stitching techniques that are designed to keep out moisture. This construction may or may not include a membrane or laminate material.

Similar to outerwear and footwear, gear can be waterproofed in a number of ways. In this section we’ll cover a few examples of how outdoor gear companies are making life easier and more comfortable in the great outdoors.

Tents

All three-season and four-season tents from reputable brands are designed to protect you from rain and moderate snow. Tent rain flies are made off waterproof or highly water-resistant materials like nylon taffeta, and usually treated with a DWR coating. For the best weather protection, look for tents that have “factory sealed” or taped seams. These tents have a waterproof material placed between overlapping seams, which are then double stitched. This technique fortifies the seam and helps eliminate any gaps where moisture could penetrate. For more information, see our Tent Guide.

Paddlesport Gear

For the best protection from ice-cold river water, kayakers should consider investing in a waterproof breathable dry top. These are loose-fitting, seam-sealed waterproof garments designed to layer over a wetsuit and completely seal out water. Dry tops often have rubberized gaskets at the neck and wrists to prevent water from penetrating during a roll. Dry bags, which are completely water-tight gear bags, are ideal for protecting food, clothing and other equipment. For more on paddle gear, check out our Kayak Guide.

Backpacks

Many backpack models now include integrated waterproof rain covers that shelter your pack from the elements as you hike and pack away when you don’t need them. Rain covers are usually made from nylon with a DWR coating, making them waterproof in moderate rain showers and snow. Check out our Backpack Guide for more information.

To get the most life out of your waterproof outerwear, you must keep it clean. Sweat, dirt and dust particles can make your gear wear out faster if you don’t clean it often enough, not to mention the funky odors that can start to develop.

Machine Washing

Most waterproof outerwear can be machine washed and dried, although you should always double-check the tag to be sure. Use a mild detergent and warm water. Avoid harsh detergents, fabric softeners and very hot water, as these can break down DWR coatings faster.

Water-Repellent Coatings

Unfortunately, you can't fix a waterproof membrane if your jacket starts to leak after several years. However, the durable water repellent (DWR) finishes on waterproof gear will start to wear out long before the membrane does. When this happens, you’ll notice that moisture no longer beads up on the surface and appears to absorb into the fabric. This will cause a reduction in breathability, and also make your outerwear feel clingy and cold.

Fortunately you can usually renew the DWR finish by laundering your waterproof outerwear according to the garment's care instructions and ironing it on a low steam setting. This will often revitalize the DWR coating, as long as it hasn’t worn off completely. If steaming no longer works, there are spray-on and wash-in DWR products available on the market that can replenish the water-repellent finish on your gear. Nikwax is a great example, and has several different products for jackets, pants and footwear. You can also check out the video above for more info.