How to build an
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How to build an
I G L O O
Igloos are a traditional snow shelter that were constructed by native peoples of the far northern regions of
Canada and Alaska. Hunters built small temporary igloos when they were away from their homes stalking game,
and larger, more elaborate igloos were constructed in areas of permanent residence. Some were even large enough
for groups of people to dance inside.
Composed entirely of rigid blocks of compacted snow carefully fitted in a spiral, igloos are incredibly shielding
from mountain weather. Insulating in the same way as a Styrofoam cup, tiny air chambers between partially fused
ice crystals enable the body heat of just a few individuals to maintain relatively pleasant temperatures inside an
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igloo even when ambient conditions are well below 0oF. No mountain tent ever conceived by a human comes
anywhere close to the storm worthiness of igloos, which can withstand hurricane-force winds. Igloos are so
weather tight that you can slumber in complete bliss while a storm rages outside. The only evidence of the previous
nights intensity is that you must dig your way out in the morning! And you can even stand on top of your creation
in the morning, after the walls have frozen. Let’s see you do that with a tent.
Despite their great utility, igloos are not currently favored as a winter survival shelter simply because of the
time and effort required to build them. If you need swift winter shelter, build a snow cave or a trench. They are
quick and easy to construct with a snow shovel, and there is a great deal of literature out there to tell you how.
Other than their utility as a base camp shelter, the reason for the modern outdoor person to build an igloo is simply:
fun. Igloos are fun to build, fun to cook in, fun to sleep in, fun to climb on top of in the morning, fun to take
pictures of, and fun to brag about later.
Before you read on, ponder these photographs, all taken in the Washington Cascades.
Time exposures:
illumination by
a single candle
How to build an
Jeremy & Jesus
join in the fun,
Cabin Creek,
above
Tumwater Canyon
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August built
igloo
in the
high country
Let’s walk, snowshoe or ski
up to the deep snow
and begin
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Choosing a site
Select a level area with uniform, deep snow for the raw material and building site. Although igloos can be
constructed on slopes, it is simply easier to quarry (cut out building blocks) and build an igloo when everything is
flat and level. The potential for avalanches must always be considered when locating a building spot. Build far away
from slopes steeper than 30o, chutes, cornices and clearcut areas. Meadows and thinly forested areas are prime
building sites.
Site preparation
With the exception of firm summer snow, the block quarry will need approximately one hour of manual
compaction and refreezing before blocks can be cut. Conveniently, the quarry will be inside the perimeter of the
igloo footprint and thus, as you cut and remove blocks from your quarry you are lowering the floor of your igloo at
the same time.
The compaction process compresses some of the
air out from among snow crystals while
friction between crystals causes partial melting.
A thirty-minute rest following compaction allows
adjacent crystals to refreeze and the snow to set
up rigidly. Low water content snows in very cold
winters can be difficult to compact; the
snowflakes will slide around like dust. However,
that is rarely a problem in the wet Pacific
Northwest, especially if you will be waiting until
spring to make an igloo, when the snow cover is
thickest and has begun to settle.
Begin compacting the quarry site first with your
skis or snowshoes on, removing them and
switching to bare boots when the snow surface
becomes unyielding. Repeat the process with just
boots, another 10-20 minutes, until again the snow
no longer yields to stamping pressure. You are now
finished with the compaction process. At this point,
the quarry must not be disturbed for thirty minutes
while the compacted crystals refreeze,
consolidating the snow mass.
Compaction Process:
Begin with skis or snowshoes
and finish with boots
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Quarrying the blocks
Begin by cutting a straight line through the center of the igloo footprint, approximately 8”-12” deep. This cut will
form the faces of the first row snow blocks, i.e., the blocks closest to the igloo center line. Note that blocks are
formed as though they are standing on edge. This cutting configuration facilitates easy extraction of the blocks by
allowing them to be levered outward with the saw (See drawing, left). Four cuts must
be made on the first block removed from the quarry: the back face, lower edge
Blocks
and both ends. This primary block is the most difficult one to
remove and often it is damaged during extraction and cannot be
First
used. Set it aside and make the three cuts for the next block:
cut
one end, lower edge and outer face. Carefully lever the
block towards the trough with the saw inserted behind
the face cut. (Continued on next page)
D IG
12”
TR
O
UG
H
Use of snow saw
to cut blocks
Igloo Tools
The indispensable snow shovel and snow saw
can be purchased from ski and climbing shops.
They can also be fabricated from household and
hardware store items, as we did back in our
dirtbag climbing days. A garden spade, perhaps
drilled out to lighten it and the handle sawed short,
will function honorably in lieu of a modern high tech
version. A snow saw can be constructed with 1/8”
aluminum sheet stock. Make the teeth aggressive
and alternately bend them to produce an offset.
Essential Tools:
- Snow Shovel
- Snow Saw
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Building the igloo
What size blocks?
Block size is a function of snow
moisture content: wetter snow
means smaller blocks should be
made. A good rule of thumb for the
high moisture content snow of the
PNW is 30” x 18” x 6”. These
dimensions can vary considerably,
but blocks much larger than that
are heavy and awkward to work
with. Cutting the blocks too small,
while imparting a finer finished
appearance to the igloo, increases
the construction time considerably.
Compromise: cut large blocks at
the bottom and gradually shorten
your block supply as construction
moves upward and the igloo
narrows.
Place the first, large snow block on the perimeter of the igloo footprint.
This first block will be resting on the leveled snow surface on its lower
edge only. With this first block you should determine if you want to lay
this lowest whorl of blocks perpendicular to grade or angled slightly
inwards; either way works. An angled in first layer produces a smaller but
more graceful looking structure while a vertical first row will generally
produce a taller, more spacious abode.
Lay the next block with its lower edge at grade just like the first block,
adjacent to it and angled slightly. Since these blocks are angled slightly
relative to each other, to make their respective ends mate nicely, it is
recommended, but not entirely necessary, to custom fit the corner edges
with the saw (See photograph below). Simply laying the unfitted blocks
together at their raw corners is adequate strength wise for most PNW
snows, but you will need to fill in all those outside corner wedges with
snow later.
Martha struggles with
a monster block
Trimming corner
prior to fitting block
The block wins
The correct technique for fitting one block against another is in two
motions. First, gently set the block to be fitted on top of the lower row of
blocks (on grade if you are fitting blocks to the lowest portion of the wall)
approx. 6” away from its neighbor. Next, in one smooth but forceful
motion, slide the block into its neighbor so that the two trimmed corners
smack into each other. In minutes the mated corners will be frozen
together. This technique does take a bit a practice; if you ram the block
with too much force, one or both blocks will split. Important Point #1: A
split or tattered block cannot be salvaged. Discard it and begin again
with a fresh block. You may break a block or two before getting it right.
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Important point #2: New blocks should contact their neighbors on the three corner edges only. This is
counter-intuitive, but following this advice will reduce the number of damaged and slipped blocks. While not
critical on the lower, more vertical blocks, it will become important as the wall grows more horizontal and force on
the new block becomes perpendicular to its face. To reiterate: the new block should contact only at the three
corner edges. Facilitate this by cutting a very slight inward curve to the edge and the end that will be contacting the
established blocks (See drawing below). This will insure that contact is made only at the three corner edges.
Laying the blocks
Trim
Cut slight
inward curves
(exaggerated
for clarity)
corn
er
Trim off upper part
of first laid block
Continue laying
blocks around the
perimeter, joining
them in the manner,
and sloping the blocks
ever more towards the
horizontal as you
continue upwards.
You will probably
want to scale down
the block size as you
approach the finished
structure.
Ken demonstrates
lightweight blocks at Lichtenwasser Lake
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Almost finished!
Note use of saw to
fit corners of new block
Don and Martha
support from inside
while a third person
works the outside
It helps to have an extra pair or two of hands when laying the final few blocks, since there is a strong tendency
for these almost horizontal pieces to fall inward. Nevertheless, one person working inside the igloo with a saw can
finish up. Shape the final, smaller blocks so that their outer face is larger than their inner face, like a flattish cork,
and they will exert outward force against neighboring blocks that will stabilize the structure. This shaping can be
done with the saw in one hand and the block balanced in its final resting place in the other hand. Note that shear
stresses on these nearly-horizontal blocks are much greater than on the blocks of the lower, vertical section.
Furthermore, significant juggling and jostling occur during fitting of the final blocks, and thus it is a good idea to
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let the igloo “rest” for five or ten minutes before fitting the final blocks. So take a break, grab a bite to eat and
allow time for the blocks to freeze solid and stabilize the structure. Don’t get too bothered if the last block
collapses into the quarry as you attempt to set it in place. Make another effort with a fresh block, reshaping the
sides of the igloo hole if need be. This is definitely the most delicate maneuver of the building process and
sometimes you just have to work it a few times to get it right.
We have certainly had our problems in this regard, as the
photograph shows. Once the final blocks are in place, you can
put the finishing touches on the ‘gloo.
Final details
Minor frustrations
before the finish
Inside perimeter gutter: While you’re inside the igloo, you
might as well cut a shallow (2”-4”) gutter around the perimeter
to catch melt water that invariably trickles down the sides as
inside air heats up with cooking and breathing.
Ventilation: An open door is not adequate by itself to
provide fresh air circulation. You will definitely need to
provide cross ventilation to keep fresh air moving in this
airtight structure. Poke a few small holes near the top of the
ceiling, and keep some snow plugs or sticks handy to regulate
temperature. If you close off the door, also poke some holes
near the base of the igloo. Ideally, these lower holes should be
located 90o from the prevailing so they will escape drifting
snow.
Entrance: An entry way can be dug anytime after the first
layer of blocks has been laid. However, it is somewhat easier to
tunnel in an opening after the quarry area (igloo floor) has been
cleaned of a layer of blocks. Hollow out underneath the first
(lowest) layer of blocks. Plan ahead so that one block spans all
the way across the tunnel and no joint is suspended. Since the
Tunneling underneath
the igloo to form the
entrance. Note the
high-tech shovel
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threat of drifting snow burying the entryway while you sleep is very real, position the door facing partially into or at
90o to the prevailing wind. Additionally, bring the shovels and saws with you into the igloo for the night. You
just might need them to dig your way out in the morning.
Filling in the joints: Although it contributes little strength wise, it gives a sense of completion to fill in all the
cracks and joints on the outside with snow. You can toss shovelfuls of loose snow on the structure and then gingerly
tamp the snow into the hollows, or push in handfuls at a time.
Once completed, you will have a fun, warm shelter that will stand up to surprising abuse.
Ken is ready to
carve a few turns
down the side
Our first igloo,
Lower Eightmile Lake, 1975.