Yes! Some level creators have designed their maps with building restrictions in mind, but you can override this in your singleplayer or server settings.
For singleplayer:
- Click the Advanced button
- Scroll down to Gameplay
- Enable Bypass No Building Zones
For server hosts:
- Open the U3DS folder, then the Servers folder
- Open the folder for your specific server
- Edit Config.txt in a text editor
- Search for Bypass_No_Building_Zones and change that line to: Bypass_Building_In_Safezones True
- (Optional) you may also want to do the same for Bypass_Building_In_Safezones.