Crude hut is the most basic and small building of all, although they are good for storage and deer traps. They are also easy to make and do not take a lot of space.
2 Walls + 1 Med Foliage [Create Tool] > Crude Hut
Another type of this building is called the Large Hut that looks similiar to the crude hut but is built by parts (e.g Corners, edge, etc) and require more space, but they are a lot bigger. Though it is a hut, spending your time in it is useless, with the exception of a storm.
2 Walls + 1 Large Foliage [Create Tool] > Large Hut