Architecture for Better Future

Starting Construction

With several uniform sized snow blocks cut, it is time to place them in a shoulder-to-shoulder circle on the circular building site that was prepared earlier. Again, make sure that these blocks are placed on a solid foundation and won't shift under the weight of the additional blocks that will be later placed on top of them. To improve the strength of the igloo, each of these blocks should be mitered, or cut at matching angles, so that they fit tightly together.

After the first ring of blocks is in place it is time to cut away a portion of several of those blocks to create a circular, vertical ramp. This ramp provides two points of contact: (1) a "shoulder" and (2) a base, which will support the inward-sloping blocks that will be added to create the dome shape of the structure. To form the ramp, start at a joint between two blocks and, block by block, cut away and discard a portion of each block. The smooth and gradual slope of the ramp should continue between half and three-quarters of the way around the ring of blocks.

Shape the top of all the blocks so that they angle slightly inward towards the center of the igloo. This slant causes the block that is placed on top to lean further inward, eventually creating the smooth arch-shaped profile of the igloo. For a beginner, it is sometimes difficult to judge the amount of inward slope to carve on top of each block. If this angle is not steep enough, the walls of the structure may not curve inward to complete the dome.

A good technique to ensure that the top of the blocks are properly angled is to place a small branch, ski pole, or other marker vertically in the snow at the center of the igloo. There should be a straight line of sight when looking along the top of an angled block toward the base of the marker. Another method to visualize the correct angle is to tie a length of cord to the base of the center marker. If the angle is correct, a straight line will be form when stretching it over the slope of a block.

Now it is time to continue stacking more snow blocks on top of the ramp. These rectangular blocks should all be the same size as the original blocks used to form the base ring. Starting at the point on the circular ramp where a full-height block meets the shortest block, place a block in tight contact with the shoulder and base. Cut the side edges of the new block so it fits tightly against the block next to it. Each block should bridge the vertical seam between the two blocks beneath it. This makes for a stronger structure. Cut the top of this — and subsequent blocks — to angle inwards toward the center of the igloo.

At this point, before the wall gets too high, it is a good idea to have a helper stand inside the igloo to assist with construction. He or she should have a saw handy to help shape the blocks, and should be prepared to remain inside until the igloo is completed. Continue stacking and shaping the blocks in an upward, inward, circular spiral until only a small opening at the very top of the igloo remains, a bit smaller than the size of blocks that have been used in construction.

It is now time to cut and place the cap block, or "king block." This block is like a cork, plugging the hole in the top in the dome of the igloo and supporting the inward leaning walls of the dome. This block takes a bit of careful shaping. Select a block that is slightly larger than the opening in the top. Taper the sides of the block to match the taper of the hole in the dome. Carefully place it into position being careful not to lean against the igloo walls, which could cause it to collapse. Placing the block requires the assistance of the person inside the dome as well as some reaching and stretching by the person outside.

Making an Entrance

With construction of the snow block dome complete, it is time to finally create an entrance. (Making the entrance before the igloo is complete weakens the dome structure and increases the chances of the structure collapsing.)

There are two choices for entryway design, depending on the depth of snow beneath the igloo: a "gopher hole" and an arch-shaped entry. When the snow depth under the igloo is at least 3 feet (1 meter) a "gopher hole" entryway can be dug. About 2 to 3 feet (60 to 100 centimeters) away from the outside wall of the igloo, dig a hole at least 3 feet (1 meter) deep. This hole should be wide enough for a person to crouch at the bottom.

At the bottom of the hole, tunnel horizontally under the wall of the igloo. It may be helpful to measure the length of the tunnel with a ski pole to ensure that the tunnel has passed completely beneath the igloo wall. When the horizontal tunnel is beneath the interior of the igloo, tunnel upward into the igloo. Since warm air rises and cold air sinks, this type of entrance prevents warm air inside an occupied igloo from escaping.

As an alternative to the "gopher hole" entrance, an arched-shaped surface entry can be cut in the side of the igloo. This method should be used when the snow is too shallow (less than 3 feet (1 meter)). The arch shape minimizes stress on the shell of the igloo caused by creating a hole in the wall. This opening should be not much larger than 2 feet by 2 feet (60 by 60 centimeters) — just large enough for a person to easily crawl through.

Choose the location of the entryway so that the arch of the opening will be centered beneath a solid snow block and not directly beneath a seam between two blocks. Structurally, this solid block header serves as a lintel found over the doorway of a house to support and distribute the weight of the structure above the opening.

Later, the igloo interior can be closed off from the elements by placing a snow block or backpack in the opening. When additional entryway protection from wind and blowing snow is desirable, a snow block windbreak or surface tunnel entrance can be built onto the opening in the igloo.

Finishing Touches

Even the most carefully built igloo will have some open cracks and gaps between snow blocks. These small openings do not significantly affect the strength of the igloo but will permit body heat generated inside the igloo by occupants to escape and gusts of wind to enter. Once the igloo is complete, these openings can be sealed by hand-packing them with loose snow.

It is important to prevent extreme heat loss from within the igloo, but some ventilation for the comfort and safety of occupants is necessary. It is highly recommended that a fist-sized ventilation hole be cut near the top of the igloo dome. During snowfall and drifting conditions this vent hole may become blocked. Occasionally check the vent, and if necessary, clear it with a hand, ski pole, or other tool.

The satisfaction in a well-built igloo — simple, timeless and evanescent, and beautiful — is virtually universal. The pleasure of sleeping inside, safe and sound from the raw harshness of wintry elements outside, may be even better.

Source : Architecture Week