An Igloo is a warm, sturdy dome-shaped structure built from blocks of snow. You can construct an igloo to use as a temporary shelter to avoid the elements. You will need a snow saw or large knife and a snow shovel or snow spade.
To Build an Igloo:
Step 1: Find a suitable spot to build your igloo. Look for an area with hard-packed snow - hard enough to make solid snow blocks. You can compact the snow yourself by tramping an area for about 20-30 minutes.
Step 2: Dig a hole or a trench so you will be able to reach the underside of the blocks to cut them free. Using your saw or knife, cut the blocks from the snow on either side of the trench. The blocks should be solid enough to be carried without breaking their own weight. The harder the snow is, the more solid the snow blocks will be. 8 to 10 inch thickness is good for the blocks.
Step 3: Smooth the edges of the snow blocks, and angle them depending on the position in the spiral where it will be placed. Start putting them in a a circle, working your way up. Stagger each row decreasing the block size as you work up to the top. Stack additional layers on top, each time situating the blocks slightly inward so that the walls form a dome. fill in any gaps as you go, pack them tightly with snow. To create your entrance, point snow blocks outward stacking them in the same way as the walls. You may prefer to make an "L" shaped entrance as it will block the wind better and help keep snow from blowing in.
Step 4: Once all of the blocks except the last one have been placed, cut a cap block that is slightly larger than the hole on top of your igloo. Wiggle the block into place and shape as needed to fit the opening.
Step 5: Shovel snow onto the igloo. Pack it gently into all the holes and crevices. Smooth out the interior walls, this will prevent dripping as the inside temperature rises above freezing. Shovel out any extra snow. Cut vent holes on the side of the igloo wall and roof to prevent suffocation and to vent carbon dioxide. You can cover your entrance with a back pack, bag of snow, etc. However leave several inches of gap on all sides in case your roof and wall vent holes get covered during a snow storm.