How Waterproof Is Your Rain Jacket?
Breaking down hydrostatic head, fabric layers, membranes, and more.
Table of contents
A waterproof rain jacket is an essential kit component for hikers, backpackers, and a multitude of other outdoor adventurers. As with any gear category, there are varying levels of effectiveness within it, including breathability, comfort, and durability. The most important measure of any rain jacket, though, is how well it seals out moisture—and the term “waterproof” is more nuanced than you might think. To help you understand waterproofing levels, get up to speed on how membranes work, and how those factors (and other design elements) act in concert to keep you dry on the trail, we’ve put together this handy guide.
Hydrostatic Head, Explained
As you peruse rain jacket specs online or in a store, you might come across a number for a shell’s hydrostatic head, or HH. Simply put, this figure, which is measured in millimeters (sometimes abbreviated as mm, or K), indicates how waterproof a rain jacket’s material is. The higher the hydrostatic head, the harder it is for water to penetrate a jacket’s shell fabric and membrane. To determine a fabric’s hydrostatic head, a laboratory test is performed in which a swatch of the material is sealed tightly over a tube filled with water. The amount of water (and thus the pressure) inside the tube is steadily increased until it seeps through the material; when it does, the height, in millimeters, of the water column inside the tube is your hydrostatic head.
Generally, true waterproofing is thought to start around 5,000 millimeters (5K), and a 10K hydrostatic head is considered the minimum for a trail-worthy rain jacket. As you increase towards the 28,000-millimeter rating boasted by the category’s most premium models, you get even more protection from unrelenting, heavy precipitation. Hikers who hit the trail only occasionally or in dry environments can probably get away with shells that fall between the 10K and 15K marks, while dedicated long-range backpackers and those getting outside in notoriously wet climates will want the reliability (and dry base layers) provided by models around 20K and up.
Rain Jacket Layers, and Why They Matter
Understanding hydrostatic head is a good place to start, but if you have to pick one nugget of information to remember about rain jackets, it should be how different membrane constructions, or layers, affect performance. The specific design element that makes shells waterproof is a membrane filled with microscopic pores that are small enough to allow air to pass through, but not moisture. Wearing a jacket that’s just made from the membrane isn’t suitable for hiking (or most outdoor activities), though, as it would rip easily and would quickly become clogged with oils, dirt, and other grime. Thus, a nylon or (less commonly in rain jackets) polyester face fabric is bonded on top of the membrane, which greatly increases a jacket’s durability. That outer shell is the first “layer” being referenced when you hear about 2-layer, 2.5-layer, and 3-layer jackets; the second is the membrane underneath, although they appear and feel like a single material.
Performance—and price—generally increase as you add more layers to a rain jacket. A 2-layer shell, the most affordable of the bunch, has an additional mesh or taffeta lining on the interior to protect the exposed membrane from wear, tear, and your body oils. However, 2-layer designs, such as the REI Co-op Trailmade ($70), are heavier, bulkier when packed, and less comfortable and breathable than their more premium counterparts, and usually aren’t equipped with high hydrostatic head fabrics in an effort to keep costs down. (Also, a quick note: laminated, ultralight 2-layer jackets do exist, such as models made with the short-lived Gore-Tex Shakedry and its successors. They don't cover the membrane with a face fabric and are impressively light and breathable, although they suffer from durability issues.)
It’s 2.5-layer jackets where you start to see designs that are light, breathable, and comfortable enough for hiking and backpacking. A 2.5-layer shell consists of a face fabric bonded to the waterproof membrane, which then has an additional, extremely thin “treatment”—commonly referred to as printed, but which can also be laminated or sprayed on—attached to the interior. As with the mesh layer on a 2-layer shell, the print on a 2.5-layer jacket increases durability, but without as severe a weight and breathability penalty. It also results in a feel that’s more supple and less crinkly than 3-layer rain jackets, which have an additional, full layer of fabric affixed to the inside of the membrane for maximum durability.
However, 2.5-layer shells, like the REI Rainier ($100) and The North Face Alta Vista ($160), which once made up the bulk of the affordable-yet-performance-oriented rain jacket category, are now being supplanted by 3-layer competitors. A full-featured, 3-layer shell is likely more comfortable than a 2.5-layer model (that extra layer of interior fabric generally feels better than a print backer, which can seem plasticky, and wicks moisture more efficiently), as well as tougher over the course of extended use—the interior won’t flake or delaminate like a 2.5-layer jacket’s will. And now, with the rise of impressive in-house membranes like Patagonia’s H2No, Outdoor Research’s AscentShell, and Black Diamond’s BD.dry that help keep costs down (as opposed to Gore-Tex), 3-layer jackets cost less than ever. For example, the Patagonia Torrentshell 3L comes in at a reasonable $189, while the Mountain Hardwear Threshold costs even less, at $180.
Yes, 3-layer jackets are usually a bit heavier and stiffer than 2.5-layer models, but the gap is growing smaller every year. And considering that 3-layer models provide better longevity (and thus, increased sustainability as well as bang for your buck), we usually lean towards recommending a reasonably affordable 3-layer hardshell unless you’re sticking to a tight budget or won’t be wearing your jacket that often. And if you plan to spend pretty much any amount of time on the trail rather than just around town, go for a 2.5- or 3-layer jacket over a cheap 2-layer one.
Other Factors That Matter
We’ve covered a lot so far, but knowing a rain jacket’s hydrostatic head rating and membrane construction won’t give you the whole story when it comes to waterproofing. As you investigate a given model’s build, pay attention to these design elements, which significantly impact how impenetrable it will seem when the sky opens up.
DWR Coatings and PFAS
Aside from membrane construction, this is the rain jacket feature that most people (and brands) mention most often when talking about waterproofing. A durable water-repellent coating, usually shortened to DWR, is the first line of resistance against moisture. It’s a polymer finish that’s applied to the outside of a jacket’s face fabric, and which causes precipitation to bead up and roll off rather than immediately soak into the material. (Material that has become sodden, and which rests uncomfortably on your body, is referred to as wetting out.) Brands usually apply their own proprietary DWR constructions to their rain jackets, which is to say that some are more effective than others. As with waterproof membrane quality, DWR performance usually improves with price.
It’s important to note that, over the last few years, more and more shell manufacturers are moving away from DWR coatings that are made with per- and polyfluoroalkyl substances, also known as PFAS. These chemicals, which are excellent at preventing shell fabric from wetting out during extended exposure, are also harmful to both humans and the environment and can remain in an ecosystem for years, earning them the moniker “forever chemicals.” It’s heartening to see the outdoor industry push to leave PFAS in the past—especially in DWRs and waterproof membranes—but the simple truth is that new, PFAS-free DWRs don’t last as long and cause face fabrics to wet out more quickly than past iterations. This isn’t the end of the world: The membrane beneath is still waterproof, and consistently washing and eventually reapplying DWR to your jacket is something you should do anyway (more on that at the end of this article).
Seam Taping
If you spring for a rain jacket that’s above the truly budget price range (basically any 2.5- or 3-layer model), it’s likely that it will feature fully taped seams. This refers to a process in which every single seam of the jacket—each of which is a potential leakage point due to tiny holes caused by the stitching—is sealed with waterproof tape to make sure that no moisture sneaks through. Low-cost, 2-layer models like the REI Trailmade or Columbia WaterTight aren’t completely seam-taped, and so you might get a little damp if you stay out during an extended rainstorm. Go up one price level, though, and you’ll find that most jackets, such as the REI Co-op Rainier, are fully sealed. (Again, we’ll repeat our recommendation to buy a 2.5- or 3-layer shell if you can afford it.)
Shell Fabric Thickness
The membrane beneath is more important for determining waterproofing, but the thickness of a jacket’s face fabric also has an effect on how well it keeps moisture out. We mostly covered this when discussing hydrostatic head, but it’s worth noting that, all other parts of their constructions being equal, rain jackets with higher deniers (a measurement of a given fabric’s thickness, often abbreviated as “D”) will feel more waterproof than lower-denier (i.e., thinner) competitors, and are also usually more durable. The flip side of those performance benefits is that thicker jackets are heavier and often less breathable, but if protection is what you’re prioritizing, a 3-layer hardshell with 60-denier face fabric will likely provide more shelter than a comparable model with 20-denier outer material.
Rain Jacket Price Tiers and Performance
As we’ve mentioned already, waterproofing tends to increase with a rain jacket’s price point. But what does that mean for real-world use? Here’s a quick breakdown to help if you’re deciding how much to set aside for a shell.
Budget ($150 and under)
The most affordable end of the rain jacket spectrum is a fine place to look for a shell that will keep you dry during brief drizzles, misty days, and perhaps even a (very) short cloudburst. These models probably have hydrostatic head ratings between 10K and 15K—definitely err on the higher side of that range if you don’t want to be overcome by moderate rain—and include 2-layer and some cheaper 2.5-layer jackets. Fully taped seams aren’t as common, and far from guaranteed.
It’s not just waterproofing that’s lower in budget rain jackets. Comfort, breathability, durability, and overall construction quality lag behind even the most reasonably priced mid-range competitors, and in truth, we really only recommend them to those who are building their kit from scratch and want to save money where they can, are going to use their jacket only in town and not on the trail, or who live in very dry environments and want a just-in-case shell. If you do go the budget route, though, we’ve vetted REI Co-op’s Trailmade and Rainier jackets, and the Marmot PreCip Eco is another popular pick.
Mid Range ($151 - $249)
Here’s where the best values in the category reside. As we touched on earlier, improvements in various brands’ proprietary membrane and fabric tech mean that there are plenty of well-made, 3-layer rain jackets out there that you can snag for less than $250. If you want to guard yourself against “average” inclement weather outdoors without breaking the bank, this is the price range to prioritize. There are 2.5-layer shells in here that are slightly less comfortable and durable than their 3-layer cousins, but the majority of the models within this range will keep you dry during, say, the quick afternoon storms that are the hallmark of monsoon season in the Rockies, or perhaps a misty day in the Northeast. Expect hydrostatic heads between 15K and 20K.
Some of our favorite rain jackets reside within the mid-range price tier. The Patagonia Torrentshell, with its 3-layer H2No Performance material, retails for only $189, and the 2.5-layer Black Diamond Fineline Stretch, with its supple feel and sub-10-ounce weight, is one of the most well-rounded models in the category. If there’s a common drawback to mid-range rain jackets, it’s usually relatively lower breathability compared to premium competitors, as well as bulkier packed sizes. But for the majority of hikers, backpackers, and other outdoor-lovers who want a do-it-all shell, you’ll probably be happy sticking in this section.
High End ($250 and up)
The most expensive jackets in the category are often specialized models, in one respect or another. We won’t go into the ultra-breathable or ultralight shells that make up part of this category—they have different priorities other than just pure protection. But for the utmost in waterproofing, which is essential if you spend lots of your leisure time in the woods or high up in the mountains, no matter the weather, you’ll probably be thankful you spent the money on a shell in this price range. A 3-layer build is guaranteed, and various versions of Gore-Tex are de rigeur.
These premium rain jackets should be on the list of any mountaineer, Pacific Northwest hiker, or conditions-be-damned backpacker. With durable materials, excellent construction quality, and hydrostatic heads that range from 20K up to about 28K, they’ll keep moisture from soaking through even during sustained, driving rain. Any of Arc’teryx’s Beta series, including the SL ($500) and the vanilla version ($400), are standout (if expensive) examples in this category, while the Patagonia Granite Crest ($289) is a more palatable alternative, price-wise.
How to Wash Your Rain Jacket and Extend Its Lifespan
If you’ve owned and used a rain jacket for multiple seasons, you might have noticed that its performance starts to suffer over time—usually, that’s in the form of the face fabric wetting out quicker than when the garment was new. That’s because dirt, body oils, and other residues can damage the jacket’s DWR or clog up the pores of the membrane, making it much less effective at beading and shedding water. Nobody wants a shell that feels soaked and lies cold and clammy against their body (even though the waterproof membrane still works), but thankfully, it’s easy to revitalize a jacket and get it back into fighting shape.
To do so, we first recommend running your shell through a normal wash, which will go a long way towards reviving the DWR and clearing the pores. Mild laundry detergents will get the job done (you don’t want a detergent that will leave residue), and you can also use a dedicated gear detergent like Nikwax Tech Wash. Make sure to avoid fabric softeners—they can clog the pores of the jacket’s membrane, making it less breathable. After you’ve dried the jacket (follow the manufacturer’s instructions on the label), hit it with a product like Nikwax TX.Direct (either the wash-in or spray variety) or Storm Care’s Eco Proofer to restore the DWR to its original power. Repeat this process at least once per hiking season—particularly the washing portion—and your jacket will live a long, fruitful, and protective life.
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