In order to understand Viking houses, buildings, and other structures, it is important to first understand something about the Viking culture. As a culture, the Vikings were predominant in the Scandinavian regions from about 794 AD into the mid-11th century. While many people consider the Vikings to be nomads and plunders of small villages (both true, by the way), they were also known for setting up colonies in those areas that they defeated through battle or ambush attacks. This is a key point to remember when considering the types of homes that they built. Another key element to keep in mind is the climate in which they lived.
All ancient peoples had to build homes and other structures that would withstand their local weather patterns. These structures, for the Vikings, had to also protect them from the severe cold that was a routine part of their annual life. To do this, the Vikings often used building techniques that they found in being used by those that they conquered. This is why Viking buildings and houses vary from one region to the next. They basically took what was being used by the locals and enhanced it to shape their own art forms and culture without destroying the underlying benefits of the structure in question.
Over time, the normal Viking house began to resemble a Viking ship in many ways. These homes often had oval sides and could house as many as 40 people at one time. There were, of course, much smaller houses, but one should not forget that Vikings often lived in large houses where the extended family all resided under one roof. These larger Viking houses also were home to any slaves the clan had captured as well as domestic animals that needed shelter from extreme weather elements. To see an example of one of these larger Viking houses, look up the Fyrkat Viking Fortress in Hobro, Denmark online. This form of house was used by a great deal of Vikings during the time period 980 AD.
One common occurrence in Viking houses is the use of poles along the side of the houses. These poles were used to support the roof as well as the walls. Roofs were often composed on wooden tiles and often covered in thatch as well to help better protect the interior of the structure.
The interior of a Viking house was fairly simple and functional. Often there would be a long bench situated along the sides of the home, a firepit would be located in the center of the room and a hole would be cut out of the roof over the pit to allow for smoke removal. If animals were kept inside, they would often be housed on one side of the house in small stables.
For those Vikings that settled in areas were wood was scarce, turf was used as the main building material. This was most often seen in Viking houses that were built in and around Greenland. Others Viking houses were built partly into the ground. The soil removed for the pit in which the house was built around was used as insulation. Generally, pit homes were built by poorer Vikings as the building materials were readily at hand. One simply had to dig it up.