How to Place and Upgrade a Prefab House
Placing the Structure
Select the structure item you want from your inventory and use it on the ground where you want the building to stand. The base tier is House. Once placed, you can move up through the upgrade chain by using an Upgrade item on the placed structure. The progression runs House → Improved House → Advanced House → Modular House, so hold the correct Upgrade tier for the building you are standing in front of.
Choosing the Right Tier
If you want a compact starter, place House. For more room and detail, work toward Improved House, then Advanced House, and finally Modular House. The same upgrade logic applies to other families: Farm → Improved Farm → Advanced Farm, Modern → Improved Modern → Advanced Modern, and Aqua Base → Improved Aqua Base. Warehouses follow Improved Warehouse, and you can also place Town Hall, Saloon, Ski Lodge, Jail, Defense Bunker, Machinery Tower, Magic Temple, Dark Watch Tower, and Mineshaft Entrance directly as standalone builds.
Practical Tips
Clear the footprint before placing so the structure does not clip terrain. Keep a stack of Upgrade items on hand so you can promote a building on the spot instead of tearing it down. Use Boundary Block to mark out or fence an area around your build, and Light Switch plus Dark Lamp or Paper Lantern to control interior lighting once the walls are up.