To Build an Igloo

A step-by-step guide
for snow in New Hampshire
(loose snow)

The igloo described here has an inner diameter of seven feet. This is big enough for two people and gear, or four close friends in a crunch. Seven feet means you can lay flat in it and not have your feet or head up against the wall. The construction took 15-20 minutes to prepare the snow, a break of a few hours, and then about an hour and a half to build. This one was build solo.

Click on any image to see it full size.

  • Preparing The Snow The traditional arctic igloo is build of snow which has been wind packed. This is snow hard enough to walk on, but soft enough to cut -- not ice. But I have rarely found such snow where I live -- so I have to make my own construction material. It is not hard to do.

    First stomp down the snow in the area where you will cut your blocks. For this igloo that was an area 4 ft wide and 25 ft long. I generally wear snow shoes to do this. If the snow is crusty I'll first need to break it up by thrashing around in just my boots, and then packing it with my snowshoes. This may seem counterproductive. But I need the snow compressed all the way to the ground. I don't want a soft layer in the middle of my snow blocks. Now I shovel more snow onto my trod down area. This is my future "quarry". I'll heap it up and pack it down until it is about two feet thick. Its thickness is dictated by the length of the saw blade I'll use to cut the blocks with. I continue to trump on the snow and shovel until the snow is firm enough to walk on top of.

    At this point it is best to go away for awhile, usually about two to four hours depending upon how wet the snow is and how cold the day.

    Marking the base

  • Marking the base When I was digging I cleared the area where I will build the igloo. The traditional methods called for building on top of the snow. This works in the arctic with a deep snow pack and allows you to dig a low entrance tunnel out of the wind. But it doesn't work in loose snow. Your final igloo will weigh hundreds of pounds and so needs to be build on a firm foundation, which means the ground.

    I use my trekking pole to inscribe a circle in the snow, with a seven foot diameter or three and a half foot radius. This is the inside dimension of the igloo. The snow blocks will go outside this circle. If you put them inside your head will rest against the snow at night -- or you will have to sleep curled up. Also you want it to be circular for the strongest igloo.

    Cutting a block off the face

    Easing the block off the face
    with the saw-blade

  • Cutting Blocks This is an important skill. This igloo involved nearly fifty blocks. Shovel away the lose snow from one of the four-foot wide ends of your "quarry". This is the face you will cut from. Now cut vertically a slice about 8 inches from the face. Cut the block in half, and cut it off from the bottom and sides. In the end you have a cube about 20'' x 24'' x 8''. You will have breakage. Hopefully you have prepared extra material. There is nothing worse then almost getting to the end and running out of compact snow.

    When you are cutting the blocks the snow should be hard enough to need some sawing, but not so hard and icy that you have to work.

    When trying to get the large block out of the quarry, you can use your saw-blade to help tip it out, off the face.

    Trimming blocks to fit together

    Stabilizing the base with snow

  • First Tier The first tier is easy, but it is also a chance to develop the skill of getting blocks to fit together. Some builders recommend that the first tier is tilted inward. I don't do this, to give me a bit more head room. If your igloo really is a hemisphere, then a 7 foot diameter means 3 1/2 feet of head room, which isn't a lot. Also tilting at the start works well if you are building on hard packed snow and digging a pit in the middle. In the arctic the "quarry" is inside the igloo.

    So start placing your blocks on the outside of your inscribed line. Already you can see the problem of square blocks conflicting with a round structure (think of "square peg in round hole"). The ends of the blocks do not fit together. Set them next to each other, near their final position, and then trim the ends to match. Now shove the blocks snug to each other. You may trim a few times as you push the blocks together.

    The weight of the upper layers will push down and out on the bottom tier. Therefore I generally toss a few shovel fulls of snow against the base to stabilize it.

    Starting the second tier, the first tier is cut as a ramp. The pole guides the amount the block should lean in.

  • Second Tier, Ramp, Spiral and Leaning-In When you finish the first tier you want to cut the first few blocks into a ramp. The reason to do this is that you want to build in a continuous spiral. This way the row of blocks you are working on will have only one free end. While building, the last block is also the least steady. At a later stage you may need to hold onto the last block with one hand. If you are in a spiral, that means only one block. If you are building rows like bricks, you will have two end to hold up at once.

    You also need to start leaning blocks in at this point. I use either a trekking pole or a ski to guide me as to how far to lean my blocks, and to stabilize the blocks. I can adjust the length of the trekking pole to be slightly more then the 3.5 feet. This addition is to account for the fact that I didn't tip my first tier in. If I am using a ski, I clamp a small c-clamp to it. Both solutions guide the shape of the igloo and also work as an extra hand when things get tricky.

    The igloo is filled with blocks

    The pole steadies the wall and guides the angles

  • Blocks Mid-air The magic of an igloo starts to happen in the third tier. But before that, I fill the igloo with as many blocks as I can. If you are working with a partner, this is less important, but if you are working solo, you need to be inside to build, but your material is on the outside. So before finishing the second tier, while you can still step over the wall, carry lots of blocks inside.

    The angles of the blocks help lock them together
    In the third tier the blocks are leaning in by 45-degrees or so and it looks like they should fall in. Why don't they? The geometry of the blocks are getting more complicated. Not only do I bevel the sides of the blocks, but the top edge of the blocks will be shorter then the base, because my circle is spiraling in. This actually helps stabilize the wall. I get the blocks to stay up with two things, I bevel the side so that the most recent block layers on top of the previous block - a little bit. The other thing is that friction will hold them in place. They have to slide to the side -- not just fall down. The way you help friction is to cut those joining surfaces such that they maximally touch. That is such that they fit snuggly. Finally, when the block is in place I lean on the block to get the snow to stick a bit. After a time the snow will actually fuse. In fact if sometime it feels like my igloo is getting shaky (like when a row of two or three block cave in) I'll walk away from it for awhile. It becomes stabler with time.
    Trimming blocks to fit

  • Spiraling in - A Third Hand

    A ski and clamp or a trekking pole as a third hand.
    At this point it is nice to have a extra hand. If you have a partner, one of you is trimming and holding the last block, while the other person is gathering up the next block. But if you are solo (and when I am practicing in the back yard I'm usually solo), it is nice to have a third hand. I use either my trekking pole or ski for this. I can wedge my pole, set to the right length, to hold up the last block. If I am using a ski (and that depends upon the type of trek), I put a c-clamp about 3.5-4 feet up the ski and lean the block on the clamp. This is a third hand.

    Looking up at the sky and the forth tier

    The blocks may be wedge tight enough to self-support
    One of the most astonishing things is that near the top, when the blocks are leaning at 70-degrees or so, they may hang there mid air all by themselves! They are wedged in so tightly that they can not (except the last one) fall out, and the last one leans on top of the others.

    The capping block

    From inside an igloo

  • Closing the Top The blocks are getting harder to shape as time goes on. From the inside they appear as squares near the ground, and then trapezoids, and now almost triangles, and at some point you would just like to cap the whole thing off. For the last block, you can shape it while it is inside the igloo and then raise it, edge first, through the top hole and lower it into position. It should be too big for the hole at that point and you will want to trim and shape it. But holding a block over your head, while crouching, is not easy, and rarely will the "key stone", fit as you hoped. Still, it locks down all the blocks and you can breath a sigh of relief, your igloo will stand, and you can fill those remaining gaps at your leisure.

    The newly cut doorway

  • Doorway and Plastering If you brought enough blocks inside the igloo before the wall became too high, or your partner was handing you the blocks, you are now encased in snow, and need to cut a doorway. Usually I run out of blocks in the middle of the third tier and need to cut my doorway earlier. You can put your doorway in any direction, but think about which way the wind is blowing, which way is downhill, or is there a tree next to the igloo. You also want to cut out the door where you are confident in the strength of the wall. Since you will be removing some support, make sure a block from the second tier will not fall in. Now cut away with your most artistic arch.

    Plastering or caulking the cracks
    Once outside you want to fill all the cracks between blocks with snow. This is called "caulking" or "plastering". Sometimes the cracks around the cap block are hard to reach and so I will just dump a shovel full of snow on top, and smooth it with the back of the shovel.

    Back inside there is one last task. Some people building sleeping platforms of snow. The coldest air drops below the platforms. This is easier and more important in big family size igloos then in the one-night seven foot one described here. But where ever you are going to sleep, you want to smooth it out right now. If a broken block, or trimmed edge is allowed to sit for a long time it can get icy and leave a very uneven surface to sleep on. And sleeping in comfort was the point of making this igloo.

    The completed igloo with the tools used; 2 saws, a trekking pole and a shovel
    Some people build entrances to block the wind, some fill the door ways with cloth flaps or a snow block. That choice I leave to you.

    I do recommend a vent and a candle. Igloos, unlike tents, are fireproof. A single candle will make it glow! On the inside, the snow is so reflective that with a single candle you can easily read.