Gore-Tex hiking boots are supposed to be waterproof, right? Well, they are—except when they’re not.

My standard hiking footwear is a pair of Vasque Sundowner Classics, which include a Gore-Tex liner. I’ve worn them in nearly every outdoor condition imaginable and most of the time they have effectively kept my feet dry, yet I’ve found myself in certain situations hiking with soaking wet feet. There are two common reasons this occurs, as well as a third potential issue that can affect heavily worn or used footwear.

First of all, Gore-Tex is a completely waterproof barrier that blocks liquid water from passing through. So unless the Gore-Tex membrane has been punctured or damaged (see third point below), it will block water from entering the boot. Gore-Tex is also breathable—it allows a small amount of water vapor (i.e. your sweat) to pass through from the inside out.

Failure Point #1: Loss of Breathability
Even in good conditions, Gore-Tex doesn’t allow sweat to pass through faster than you produce it, especially when you’re exerting yourself. This is especially true for your feet, which are the second sweatiest part of your body after your armpits. And this limited breathability is completely eliminated if the surface of your boots gets saturated with water, which is inevitable in sustained wet conditions. Once this occurs, you’re essentially trapping all of your foot sweat inside your boots, which can build up enough over a day’s hike to make your socks feel noticeably damp.

Failure Point #2: Your Socks
The second common reason has to do with the fact that there is a giant hole in your boots. You know, that spot where you stick your feet in. Out of that hole emerges your ankle and lower leg, which are covered by a sock. And that sock is a moisture-sucking conduit straight into your boots. If you’re hiking for prolonged periods in heavy rain, postholing in snow, tromping through tall wet grass, or any other number of situations that expose your socks to moisture, they will get wet and start wicking water into your boots.

When it comes to hiking for prolonged periods in such conditions, you can wear rain pants that extend over the top of your boots, or waterproof gaiters that cover your boot tops and ankles, or you can even wear both. I’ve tried it all. And in my experience, these methods do help—but they only delay the inevitable.

If you’re just wearing rain pants, water slowly works in from underneath. If you’re just wearing gaiters, water slowly leaks in from the seals on top, bottom, and/or closure system. If you’re wearing both, you’re creating a sweat box around your lower legs that is both unpleasant and amplifies your own internal moisture production—and water still slowly works its way in through the gaiters.

Failure Point #3: Gore-Tex Damage
The final reason Gore-Tex boots leak is because the Gore-Tex membrane itself is compromised in some way, either from footwear use and abuse which results in a puncture or small tear or because of manufacturer defect (the least likely cause).

It generally takes a lot to damage a Gore-Tex membrane in hiking boots, given that it’s sandwiched between the boot liner and outer fabric and not directly exposed to the environment, so odds are this is not the reason why your feet are getting wet—even though this is the conclusion many folks first leap to.

Photo: Kathrin Marks; Flickr Commons