Modern Building

Stone buildings are most common. All a crafter needs to know is how to meld stone from the ground, and could make a stone home. It's also safer to have stone than grass because of aerial attacks from flying creatures. This is why older castles are more caves than buildings. Wood is harder than most stone, and more unwilling to be melded. Modern homes use Kolzire (a crystalline metal) to build their homes.
While most castles/homes were made underground, there are cases of above ground structures. There are also forts/castles/home/etc build into floating ground. This provides mobility and protection from subterranean attacks.