Snow Mounding
Part of Emergency Shelter
Proper mounding technique determines whether your quinzhee stands solid or collapses during hollowing — the pile itself is the foundation of the entire shelter.
The Science of Sintering
When you pile snow, the individual crystals are loosely stacked with air gaps between them. Over time, the contact points between crystals begin to bond through a process called sintering. Temperature gradients within the pile, pressure from the weight above, and the natural tendency of ice to minimize surface area all drive crystal bonding.
This is why settling time matters: a freshly piled mound is just a heap of loose snow. After 1-2 hours of sintering, it becomes a cohesive mass that can support its own weight even when hollowed.
Factors that accelerate sintering:
- Warmer temperatures (closer to 0 C) — molecules move faster
- Mixing snow types — different crystal shapes interlock better
- Compaction — more contact points between crystals
- Higher humidity — moisture at crystal contacts promotes bonding
Factors that slow sintering:
- Extreme cold (below -20 C) — bonding slows dramatically
- Dry, powdery snow — uniform crystals with fewer contact points
- Large air gaps — crystals not touching cannot bond
Choosing Your Site
Ground slope: Flat or nearly flat (less than 10 degrees). A mound built on a slope will settle unevenly, creating thin walls on the uphill side and excessively thick walls on the downhill side.
Wind protection: Build in the lee of a hill, tree line, or rock formation. Wind erodes the mound during settling and during the nights you sleep inside.
Snow depth: You need enough snow within a reasonable radius to build your mound. For a 2-person quinzhee, you need roughly 8-10 cubic meters of snow. That sounds like a lot, but it is only a circle of snow about 5 meters in diameter scraped down 40 cm deep.
Hazards above: No dead branches, no steep slopes above that could avalanche, no overhanging snow cornices.
Mounding Technique Step by Step
Step 1: Mark the Base
Stamp out a circle in the snow to mark your mound’s footprint. For a 2-person quinzhee, make this circle 3 meters (10 feet) in diameter. Use a stick as a compass — hold one end at the center, stretch it to 1.5 meters, and walk a circle.
Step 2: Gather Snow
Start shoveling or scraping snow from OUTSIDE your marked circle toward the center. Work in a ring pattern, taking snow from all directions to avoid creating deep pits on one side.
Gathering radius: Collect from at least 2 meters beyond your base circle. This creates a shallow trench around the mound that also serves as your entrance corridor later.
Layering technique: As you pile, alternate between different snow layers if visible in the snowpack. The surface crust, the mid-layer, and the ground-level snow often have different crystal structures. Mixing them produces faster and stronger sintering.
Step 3: Build in Stages
Do not try to pile all the snow at once into a tall, narrow cone. Build the mound in stages:
Stage 1 (base layer): Pile snow across the full diameter to about 60 cm (2 feet) high. Pack it down by patting with the flat of your shovel or walking on it carefully (step lightly and distribute weight).
Stage 2 (middle layer): Add snow to bring the center up to about 1 meter (3.3 feet). Begin shaping into a dome — the sides should curve, not rise vertically. Pack this layer firmly.
Stage 3 (top layer): Build the peak to your target height (1.5-2 meters). The top should be rounded, not pointed. A pointed peak will be too thin to hollow safely.
Step 4: Shape the Dome
The ideal quinzhee profile is a flattened hemisphere — wider than it is tall. Viewed from the side, it should look like a turtle shell, not a cone.
| Measurement | 1-Person | 2-Person | 3-4 Person |
|---|---|---|---|
| Base diameter | 2.5 m | 3.0 m | 3.5 m |
| Height | 1.2 m | 1.5 m | 2.0 m |
| Height-to-diameter ratio | 0.48 | 0.50 | 0.57 |
Avoid these shapes:
- Too tall and narrow — sidewalls become too thin when hollowed
- Too flat — not enough interior height for sitting up
- Lopsided — uneven settling creates weak spots
Step 5: Pack the Surface
Once shaped, pack the entire surface by slapping it firmly with the flat of your shovel blade. Work systematically from bottom to top. Each slap compresses the outermost 5-10 cm, creating a denser, stronger shell.
Do not overdo this — extremely hard-packed surfaces can form an ice crust that prevents the interior from sintering properly. Firm but not glazed is the target.
Step 6: Insert Guide Sticks
Before walking away to let the mound settle, push 12-15 sticks into the mound from outside. Each stick should be exactly 30 cm (12 inches) long — the minimum safe wall thickness.
Space them evenly across the dome: roughly 4-5 around the base, 4-5 at mid-height, and 3-4 near the top. Push each stick perpendicular to the surface until it is flush with the outside. When hollowing from inside, hitting a stick tip tells you to stop digging in that direction.
Guide sticks prevent cave-ins
Without guide sticks, it is very easy to hollow the walls too thin, especially near the top where the dome curves sharply. Walls thinner than 20 cm are structurally unreliable and provide poor insulation. The guide stick method is the single most important safety measure in quinzhee construction.
Step 7: Wait
Set a timer or note the sun position. Minimum settling times:
| Temperature | Minimum Wait | Recommended Wait |
|---|---|---|
| 0 to -10 C | 1 hour | 1.5 hours |
| -10 to -20 C | 1.5 hours | 2 hours |
| Below -20 C | 2 hours | 3 hours |
Use this time to gather floor insulation (pine boughs, dry grass), collect firewood for an exterior fire, eat, hydrate, and rest. Mounding is hard physical work — you will be sweating. Change into dry base layers before entering the finished shelter or you will be dangerously cold.
Manage sweat during mounding
Shoveling snow is intense exercise. Open zippers, remove layers, and pace yourself to avoid soaking your clothing with sweat. Wet clothing in winter conditions can cause hypothermia once you stop moving. Change your base layer if possible before entering the shelter.
Estimating Snow Volume
A practical rule of thumb: your finished mound should be roughly 3 times the interior volume you need. Two-thirds of the mound remains as walls, floor support, and ceiling.
For a 2-person quinzhee:
- Target interior volume: ~3 cubic meters
- Mound volume needed: ~9 cubic meters
- Snow source area (scraped 40 cm deep): roughly 22 square meters — a circle about 5.3 meters in diameter
Key Takeaways
- Mix snow from different layers for faster, stronger sintering — different crystal types interlock better.
- Build the mound in stages (base, middle, top) and pack each layer before adding the next.
- Shape as a flattened dome (turtle shell profile), not a cone or steep-sided pile.
- Insert 30 cm guide sticks from outside before settling — they are your wall thickness safety margin.
- Settling time is mandatory: 1 hour minimum at moderate cold, 2+ hours below -20 C.