Nope, the building aspect is just for the player to rest, craft stuff and respawn.
You can build your base as functional or as expressive as you want.
The game is about exploring a huge world, moving from biome type to biome type and using resources to improve your equipment and stats.
The only defence object is a row of wooden spikes you can put on the ground, you can build walls and towers (piece by piece) or dig a moat if you want.

This encourages you to explore and to set up outposts, but you can make a large lavish hall if you want. (see the Build of the Month pinned topic above for examples)