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What the Hell Do Those Ratings Mean?

Static-column test

Static-column testing is the most widely used waterproof test. A 1-inch-diameter tube stands vertically over a piece of material. The tube is filled with water, and the water's height in millimeters when leakage begins becomes the waterproof rating. A piece of fabric that can withstand 20,000mm of water pressure will have a rating of 20,000mm or 20K.

What do these ratings mean for real-life situations? Here's a general run-down:

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In spite of these ratings' seeming simplicity, it's best to take them with a good dose of salt. Widely varied testing conditions prevent across-the-board consistency. You'll see questionable 40000mm+ outerwear ratings from time to time, and many gearheads will argue that a fully taped 5000mm-rated jacket will keep you just as dry as a 20000mm-rated one. The most accurate ratings comparisons can be made between garments within the same brand.

Non-porous materials that will fail structurally before leaking. Think garbage bags, dry bags, tarps, rubber galoshes. These materials are literally waterproof, but they don't breathe. If worn as outerwear, they'll make you sweat your butt off.
Guaranteed waterproof during extended pressure and shallow submersion. Think surfing and sailing watches, high-end mountaineering jackets, and waders.
Generally waterproof, unless subjected to considerable pressure. Most high-end bike-messenger bags and rain and snow-sport jackets fall in this category.
Rainproof, but not under pressure. Think duct-taped wallets, leaky umbrellas, coated softshells, and low-tech snow-sport jackets
Rain resistant, but not rainproof. Think iPhones, basic stretch-woven softshells, and DWR-treated flannel.
Not waterproof at all. Think Grandma's panty hose, bad Christmas sweaters, old cotton tees.

How Does Construction Affect Waterproofing?

Short answer: Greatly

Ratings offer a vague notion of waterproof protection, but understanding construction is a much better tool for comparing and choosing outerwear.


A 2L (two-layer) garment consists of a face fabric bonded to a waterproof breathable membrane.

Pros + Cons

The upside: 2L pieces are lightweight, breathable, and packable. The downside: They leave the waterproof breathable membrane vulnerable to abrasion and soiling. A 2L jacket might be a good choice for you if a) you're not terribly concerned with long-lasting waterproof protection or b) you're very concerned with packability. Compare a 2L garment to a hardback book that's missing one of its covers.


2.5L garments protect the membrane with a partial protective spray or coating.

Pros + Cons

The upside: They're a compromise between 2L and 3L. The downside? See previous statement. A 2.5L might be a good choice for you if you're concerned about both packability and waterproof durability. Think of a 2.5L garment as a book with one hardback cover and one paperback cover.


3L garments consist of a face fabric bonded to a waterproof breathable membrane that's backed with a protective scrim.

Pros + Cons

The upside: They're very durable. The downside: They're generally thicker, stiffer, and less breathable. A 3L jacket might be a good choice for you if you plan to use it heavily and waterproof durability is your main concern. Think of a 3L jacket as a hardback book.

Taped Seams

There's not much point in springing for a high-tech waterproof breathable membrane if water can seep in past the stitching.

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Waterproof tape stops water from leaking through these potential entry points—kind of like caulking a bathtub.

Welded Seams

Welded seams join panels of fabric via gluing or ultra-tech sonic bonding for a seam that's stretchier and less bulky than a taped seam and significantly more resistant to water pressure.

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If you're serious about staying dry during downpours and deep days, fully taped or welded seams are the way to go.

PU Laminates

PU laminates move moisture via an absorption-diffusion-evaporation process.

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The downside: this evaporation is somewhat slower than the bead-and-roll-off effect, and in heavy precipitation some PU laminates can give you a damp feeling. The upside: PU is very durable, often not requiring a protective scrim, and leading PU laminates are giving PTFE membranes some stiff competition performance-wise.


This is the same stuff used to coat non-stick frying pans. PTFE membranes work by causing water to bead and roll off.

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The upside: These membranes have long been considered the holy grail of waterproof materials—think GORE—TEX ©, eVent, and Mountain Hardwear's Dry.Q Elite—though some PU laminates are offering stiff competition. The downside: PTFE isn't extremely durable, and when contaminated loses much of its waterproof power. PTFE membranes generally require a protective scrim.

DWR (durable water repellent)

This polymer is applied to virtually all face fabrics (i.e. a garment's outermost fabric). It penetrates the face fabric's fibers and causes water to bead up and roll off.

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DWR is a pawn in the waterproof game of chess—it serves as an initial defense, since water can still move through gaps in the face fabric's fibers.


Denier refers to a fabric's fiber density.

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A higher denier can increase water-resistance in backpacks and tent floors, but it's mainly a measure of a fabric's strength, and not really relevant when determining the waterproofness of outerwear.

How to Care for Your Waterproof Outerwear

Want to get the most out of your outerwear? Notice a decrease in waterproofness?

Step 1 Wash it Why?

Washing your jacket removes oils and grime that can compromise the waterproof breathable membrane.


A second rinse cycle will help clear away any remaining grime, oil, or detergent.


Front-loading washing machines are easier on seams.

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An outerwear-specific detergent, like Nikwax TechWash or Granger's Performance Wash, will help protect the DWR and the waterproof breathable membrane.

Step 2 Dry it Why?

Tumble drying helps redistribute DWR treatment, restoring your garment's water-resistance.

If after step 1 and 2 your jacket still isn't beading properly...

Step 3 Re-DWR it Why?

Repeated wear and washing will eventually deteriorate the face fabric's DWR treatment.


For best results, only re-DWR a freshly washed and dried garment.


Wash-in waterproofers are more likely to affect your garment's breathability than spray-ons.


Spray-ons are harder to apply evenly than wash-ins.

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Read the care label. Almost all waterproof shells benefit from washing and drying, but some garments have insulation, linings, or trims that require special attention.