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How to Make an Emergency Snow Shelter in 3 Steps

Being able to build a snow shelter quickly is a potentially life-saving skill — and one that’s a lot of fun to get out and practice.  Here’s how to build a simple shelter, called a Snow Trench, in about 20 minutes (for when the minutes count).  I’ll also cover a variation on the roof that earns this type of shelter the alternate name “Dog House”.

I like to teach the Snow Trench in 3 steps.  Read on for all the background and details, or check out our 3-part Snow Trench video lesson:

How Can Snow Keep Me Warm?  It’s Freezing (Literally)!

If you fill a can with fresh snow and let it melt at room temperature, how much water will you have?  While it depends on how ‘wet’ the snow conditions are, here in Colorado a fresh deep-winter powdery snow can yield only 10% water.  (So if your can is 10″ high, you’d have 1″ of water once the snow melts.)  Wha-?!  What makes up the rest of the volume of snow?

The answer is what gives (frozen) snow its ability to keep you warm:  air.

The supreme quality of insulation (be it in a sleeping bag, down jacket, wool blanket, etc.) is the dead air space.  And snow is full of it!  Snow makes a fantastic insulator – as long as you can keep it from melting (for example, from your body heat).

Safety & Comfort Tips

Snow can save your life, but it can also be deadly.  A handful of people die in avalanches in Colorado annually.  In descending order, the causes of death are asphyxiation (running out of oxygen), suffocation (airway clogged), and then trauma.  When digging a shelter, the snow isn’t typically chasing us at 40 mph, so death by trauma is unlikely, but asphyxiation and suffocation are very real dangers — especially if our shelter collapses.  In the event of a collapse, we have about 3 minutes to get that person out before they die due to lack of oxygen.

Here are my two biggest safety tips when building or sleeping in a snow shelter:

  • ALWAYS* have a safety buddy:  No one should ever be working on a shelter alone.  I recommend that when one person is head-first inside a shelter, at least one is standing-by, shovel in-hand, prepared to call for help and start digging immediately if the shelter collapses.  (*During practice.  If you’re alone in the wilderness you’re…well, on your own.)
  • ALWAYS maintain an air hole.  This is most important once you ‘close the door’ (see below) and turn in for the night.  It’s possible to build a snow shelter so air-tight that you’d cut off an outside air supply.  If that happens, you’ll slowly exchange oxygen for carbon dioxide with every breath you take (eventually leading to asphyxiation).

A Snow Trench is a good shelter to start with, because these safety dangers are drastically limited compared with a shelter like a Quinzhee or Snow Cave.  As you’ll see, the trench is wide open during construction and only roofed at the end (versus tunneling into snow as with the other two).

I’d also suggest dressing appropriately for the activity.  Sound silly?  You might be surprised at how few clothes you want to wear when building a snow shelter.  Digging a snow shelter is a rigorous activity that increases our respiration and heart rate, as well as our body temperature.  That can be great news if it’s really cold outside — but BE FOREWARNED:  you want to minimize your sweating and, more importantly, how wet you get your clothes, especially your insulating layers.

I typically shed a layer or two, opting for just a synthetic base layer and waterproof shell (if I’m working directly on the snow) OR my standard wool pants and flannel.  (Check out our separate post on clothing and materials.)  If you’re practicing at home, it may not be a big deal to get your clothes wet but if you’re in a more volatile situation, like far from infrastructure in the wilderness, you’ll want to protect your insulating layers — keep them nearby but safe and dry, to don once you stop moving and need the extra layers around your body.

What You’ll Need/Want to Build a Snow Trench

In a pinch, you can improvise with almost anything you can find (even your own hands to dig), but here are a couple items that will make this job much easier (and more fun!).  Best to learn and practice with the right gear.  In roughly descending order of importance, I’d want:

  • Avalanche (“Avy”) Shovel – These are lightweight, compact shovels carried in the backcountry for use to dig victims out of avalanches in a hurry.  But they’re also the perfect tool to build shelters, get around in tight spaces, and slab out snow.  If you’re buying one (and want to count on it), avoid the cheap $20 shovels that are made to look like Avy shovels but are meant to keep in your car (like, ahem, the Lifeline brand).  A decent Avy shovel retails for $60 to $110.  I like Black Diamond’s shovels, but there are a lot of options out there.  Backcountry Access is another dependable brand I’ve used.
  • Tarp – makes the job of adding a roof to your trench MUCH easier.  I tend to avoid one-time-use tarps/ponchos like the $2.99 plastic roadside ponchos.  They just get trashed, even in the process of making your shelter, which means you’ll have snow falling through.  I favor a 6 x 8 or 8 x 10 heavy duty tarp.  They’re fairly inexpensive but the downside is, they’re heavy.  But they take a beating and keep going.  (In winter, I tend to pull my gear on a sled, so an extra pound here or there isn’t the same as on my back.)  A middle-ground choice would be a more expensive, lightweight ‘military’ style poncho, a backpacking tarp, or even a piece of Tyvek.
  • Roof Structure – Branches will work, but you can also use your ski/trekking poles, skis, sled, or anything else that’s rigid and long enough to cross your trench
  • Snowshoes or Skis – will primarily be used for stomping down the ground before you dig and for walking around your trench without caving-in the sides.  I use snowshoes more frequently that skis and prefer these lightweight military magnesium snowshoes, which are a modern version of the old-school wooden ones.
  • Probe – Definitely learn to improvise with a stick, but a proper avalanche probe glides in and out of the snow effortlessly.  In our case, we’ll be probing for rocks, downed trees, etc. but probes are specifically designed to search for bodies/victims after avalanches.  Most will also have a depth gauge along its length, so you can get a solid reading of how deep the snow is.
  • Snow Saw – I’ve never gotten into the habit of using a snow saw, but they quickly earn their value in conditions where the snow will slab out nicely (if you want to cut blocks for the Dog House roof or for building an Igloo, etc.).

I want to add SNOW to this list as a necessary item, but I think that goes without saying.  I’ve built a Snow Trench in as little as 8″ of snow, but 18″ to 24″ is ideal.

How to Build Your Snow Trench Shelter

Step 1 – Select a Location & Dig the Trench

Summary:  Dig a coffin-sized box in the snow.

Specifics:

  • Look around for a proper location, including all the usual campsite selection ideas (avoid windfall/widowmakers, protected from wind, etc.)
  • Using your probe (or a stick), poke around the area.  You’re feeling for any unseen obstacles, like boulders, fallen trees, etc.  If you hit something, move to another location, until you find a clear area large enough to dig your trench (coffin-sized).
  • Stomp around the area to slightly compress the snow.  This is where snowshoes really shine.  In a pinch, drop some tree branches/conifer boughs on the area and step on them.  (Anything to spread out your weight over a larger area.)
  • Early on, it’s helpful to trace out the area where you want to dig.  Be specific.  Make the perfect rectangle.  Your probe is helpful for this.  (Later on, you’ll be able to visualize the perfect coffin without drawing it.)
  • Dig.  The ideal trench will be slightly wider than the shoulders, slightly longer than the height, and deep enough for a bit of ‘nose room’.  For the average adult, that’s about 24″ wide, 7-feet long, and 18″ deep.  Note:  As with any body-heat-warmed shelter, the smaller the better.  But there’s a tendency for the roof to sag a bit (especially the first time you build one), so adding a bit of extra depth will make you happier the first time you sleep in one.
    • Pro Tip:  Use the blade of that Avy shovel to create clean, shear, vertical sides to the trench.  Shear sides will be stronger and will ‘ice over’ more quickly.

 

Step 2 – Add a Tarp or Snow Slab Roof

Summary:  Cover the trench by any means available.

Specifics:

  • Tarp Roof – if you have a tarp (or tarp-like item) you’ve got it easy
    • Collect branches, ski poles, etc. that are long enough to lay across your shelter and overlap about a foot on either side (i.e. for a 24″ wide trench, use branches at least 48″ long).  Longer is better, in this case.
    • Lay the branches across the top of your shelter.  The more the better.  It’s not too much to completely roof-in your trench with just branches.  (But usually 5-8 stout branches will support the weight of the roof.)
    • Optionally:  You can lay additional branches perpendicularly to the original branches (parallel to the sleeper) so that you form a grid of roof structure.
    • Cover the branches with your tarp.  Pull it taut.  It’s helpful to weight-down the outer edges/corners with rocks, branches, or chunks of snow.  You want it overlap at least a foot all around your trench.
      • Pro Tip:  If your tarp is long enough, leave enough to drape over the end that will be your doorway.
    • Cover with snow!  Provided that your roof structure is strong enough, start shoveling.  Aim to cover the tarp with at least 12″ of the white stuff.  More (insulation) is better.  Chunks are fine.  But you want the roof-snow to be consistent (no huge 6″ air pockets).  So busting down clumps, or aiming for loose snow can be best.
      • Pro Tip:  Just go for it.  No one likes a lazy-shoveler.  Haul some snow.
  • Flat, Natural Materials Roof – if you don’t have a tarp, no worries.  You just have a little more prep work ahead of you.
    • After creating that grid of branches, add more.  And then more.
    • Then cover those branches (structure) with tree branches.  Evergreen coniferous (pine, fir, spruce, cedar, etc.) boughs are best, as they maintain their foliage during the time of year that snow tends to fall (they’ll have more surface area to catch snow than their deciduous counterparts).  Here in the high-country of Colorado, that’s a no-brainer, as it’s about all we have to work with (on a large scale) in the mountains.
      • Go back and cover it with more.  And then more again.  You don’t want snow sifting down on you through the night.
    • Cover with snow!  (See above.)  You may wish to be a little more gentle with shoveling the snow, as pressure may force more snow through the boughs.
  • Snow Slab (Dog House) Roof – Impress your friends.  Amaze your enemies.  Build a peaked roof from snow.
    • If conditions are just right, you can cut out large blocks of snow that are cohesive enough to lean against one another.  They’ll structurally support each other, giving you a peaked roof (and higher ceiling — meaning your original trench could be shallower).
      • Pro Tip:  Before beginning your Snow Trench, search for a good ‘quarry site’, an area that will yield solid blocks of snow.  My goal is to cut slabs that are about 24″ x 24″ and around 8″ deep/thick.  Here in Colorado, finding a quarry site usually means scraping off the top 4-6″ of fresh, powdery snow and looking for the more solid, compacted snow.  If you’re in a wetter climate, you may be able to quarry right from the surface.
        • Cut a couple of test pieces, even 12″ x 12″ to check whether the snow is good for slabs.
        • Hint:  Ideally, you can locate a quarry site right next to the perfect campsite, so you don’t have to transport slabs very far.
    • To cut a slab:
      • Slide the blade of your shovel (or snow saw, survival stick, hand, etc.) VERTICALLY into the snow.  And again.  Carve a square in the snow.  Aim for 24″ x 24″.  Go around the perimeter again.
      • Slide the shovel HORIZONTALLY under the entire area you’ve just cut into.  You’re aiming to loosen the snow beneath.  If you’re using a snow saw, you can use a sawing motion.  With a shovel, continually reinsert the blade to separate the slab from below.  Once you feel you’ve separated it, move on.
      • Set aside your tools.  Carefully slide both hands/arms under the slab.  Lift the slab, supporting as much as you can.
        • If it breaks immediately, find a different area (or be gentler with your second attempt).
        • If only a corner breaks loose, you can still totally make use of the slab.
      • Move the slab to your trench.  I like to stand my first two slabs along the rim of the trench at opposite sides on the head end (opposite the door).  If you’re careful, you can balance each slab vertically.
      • Once you have two slabs:
        • I prefer to offset the two slabs by about halfway (to make leaning the future slabs easier).
        • Enter the trench and kneel down.
        • Begin to tilt both slabs towards each other/you.  Support them as you tilt.  This is arguably the most difficult part of the whole process.
        • Slowly tilt both together until they rest against one another.  Gently release and move away.
          • If they collapse, clear the debris and return to cutting slabs.
      • Cut and add additional peaked slabs.  If you offset the first two, you can add one at a time, alternately, overlapping it by half on the last one.  (You’ll see it’s much easier to add one at a time than two at once.)
    • Continue adding slabs until you’ve covered the length of your trench, and then some.  (If you’re cutting ~24″ slabs, it should take about 4 per side (8 total) to provide a roof for your Dog House.)

So, you’ve got a trench and a roof.  At the very least, you’ve got insulation around most sides.  But if you hope to actually sleep tonight, read on.

 

Step 3 – Door, Safety & Bed

Summary:  If you really want to survive in this thing (or be remotely ‘comfortable’), here’s how you do it.  Make a bed.  Poke an airhole.  Close the door.

Specifics:

  • Make a door’way’
    • If you were fortunate enough to have enough snow to dig a trench/coffin straight down (four complete sides), you’ll need to make an opening at one end.  Often though, we’re on an incline/snow bank, or in shallow enough snow that one end is already open.
      • If you have a complete trench (no obvious doorway):
    • Carefully carve (shovel, saw, or stick) the smallest possible hole that you could fit through.  I like to try to remove the ‘door’ as one complete slab, similar to the Dog House roof, above, but you’ll be cutting it out vertically.  Set it aside.
    • When you’re ready to call it a night:  (After the bed and airhole, see below.)  Crawl inside and pull that snow-slab-door into place.  Plug any holes with chunks of snow and seal it off as much as possible.  (You’d be amazed at how small of a hole can create a draft — and lose you precious heat.)  Don’t have a cohesive door?  Plug the doorway with your backpack, tarp, boughs, or anything you can find.  Whatever you do:  seal it off.
  • Build a Bed
    • Collect sticks/branches/trees (here at our Field Site, Aspen is the go-to).  Ideally, they’re straight, around 2-3″ diameter, and mattress-length (6-7 feet).  Lay them into the trench, tightly against one another.  While it won’t provide a lot of airspace-insulation, it will get you off the snow.
    • Build a mattress out of finer branches, especially coniferous boughs.  Create a matrix, criss-crossing the logs beneath.
      • Trivia:  Ever hear the term ‘spruce it up’?  It comes from the history of building beds from spruce boughs.  Sure, spruce is pokey, but it’s way better than sleeping on the cold ground or snow.  After sleeping on boughs for 3 or 4 days, they lost enough loft (compress) that they begin to become uncomfortable.  ‘Spruce it up’ would mean adding a fresh layer of spruce boughs to the top (or replacing the mattress altogether).
      • Pro Tip:  Orient conifer boughs upside-down.  On genus’ like Firs (whose needles grow roughly in a plane), the needle-tips will then point down.  On the Spruces and Pines, whose needles grow all around, it won’t help as much but maybe a little.
  • Safety
    • Maintain at least one airway:
      • As noted above, it’s entirely possible to build a snow shelter so airtight that you can asphyxiate from oxygen/carbon-dioxide exchange.  While you want to seal your door against drafts, it’s absolutely necessary to maintain airflow.
      • Poke a hole:
        • Around 2-3″ diameter
        • On the leeward (away from the wind) side of your shelter
        • Relatively close to your head
      • Maintain it:
        • Keep a stick/pole inside your shelter.  Throughout the night, check that the airway is maintained by reaming it out from the inside.
        • Even a dusting of snow overnight can block your airflow.  Don’t let the stress keep you from the all-important sleep, but every time you wake, check the airflow.  Poking more than one hole is advisable.
    • Signage:  If you’re surviving in a snow shelter, it’s likely that you’re in a fairly remote location (far from other people/activity), HOWEVER, you need rescuers to both be able to find you AND not drive over your shelter.
      • Getting Found
        • If you’re near a trail/open area – Create obviously-human-disturbed signs.  Bright colors/clothing.  Signals visible from above.  Things that won’t be buried in additional snow.  If off-trail, create a simple sign post that indicates your direction.
        • Create a sign/disturbance immediately on top of your shelter.  “Here I am!”  Snow shelters have been known to be SO insulative that rescuers standing immediately outside the shelter screaming, can’t be hear from within.
      • Not getting crushed
        • While snow shelters can be ridiculously-strong, there have been multiple fatalities of snow-shelter-sleepers because of snow-mobile rescuers (or moose) traveling overtop the shelter and falling through.
        • Clearly demarcate the location of your shelter – vertical sticks/poles shoved into the snow creating a ‘fence’, skis poles in a vertical X, trail tape, etc.  Whatever you can do to create a “Hey, don’t go here” sort of sign.

 

So there it is.  Go out and dig yourself a survival snow shelter.  Practice hard and the rest will be easy.  Don’t wait ’til the snow hits the wind.  Get out and do it.  Or come see us for a course.

Dig hard.  Sleep fast.

 

Like this post?  Check out our video on How to Build a Quinzhee group snow shelter:

 

 

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