During the Viking age, most dwellings were longhouses (langhús). They would be built from wood if they could be, but where wood was scarce they would use whatever materials were at hand. Some had large portions of their base walls built of stone. Some were made mostly using turf, cut pieces of sod covered with grass piled high like large bricks. Sometimes the roofs were made from turf, giving them a grassy, often living, roof.
Starting from as small as 15 feet wide and 50 feet long, wealthier owners could have their longhouses as large as 25 feet wide by 250 feet long. They needed to be large because not only did they do a lot of things in the house, but they also usually let the livestock sleep in it as well. Often they would have one end walled off for the livestock, but sometimes they would just let them roam the house.
Larger houses might have a few rooms, but a typical small one would just have one large space with a long firepit in the center that would be used for heating, cooking, and light. A few tables could be moved to where they would be needed, and there would be benches against the walls for working and sleeping. Very few people would have beds, and bedding mostly consisted of furs and blankets.
Hurstwic is an excellent source of information, and they have a page dedicated to longhouses.
The site Life in Norway has an article on longhouses.
This page has a lot of general cultural info: Vikings History: An Overview of the Culture and History of the Viking Age