Last Fortress: Underground Base Expansion and Facility Guide

To expand your base in Last Fortress: Underground, start by clearing rubble immediately around your central command area, then establish your essential utility structures: the Power Generator and the Water Purification Plant. Maintaining a reliable power grid and a surplus of food and water is mandatory before adding more survivors or expanding into advanced facilities.

Clearing Rubble and Shelter Layout

Reclaiming usable subterranean floor space requires systematically clearing rubble throughout your shelter. Uncleared debris directly blocks room placement and prevents facility expansion.

Central Command Focus: Prioritize removing rubble directly adjacent to your central command hub first. This centralizes worker activity and reduces travel time for resource collection.
Deeper Level Routes: After clearing the central hub, open pathways down toward deeper subterranean levels. Deeper shelter zones contain specialized slots needed for advanced machinery that cannot fit into starting areas.
Footprint Management: Clear specific tiles only when you have the immediate resources and worker capacity to construct a new facility or upgrade an existing route.

Power and Resource Facility Setup

Resource management relies on balancing electricity, water, and food. The Power Generator is your base's most critical facility because secondary structures, including water pumps and sleeping quarters, shut down entirely if the power grid fails.

Facility Type	Construction Priority	Primary Function	Dependency
Power Generator	High (First priority)	Supplies electricity to all shelter structures	Requires assigned technical survivors
Water Purification Plant	High (Second priority)	Provides essential water for base population	Requires active electricity supply
Food Production	Medium	Sustains survivor morale and population growth	Requires power and water supply
Research & Defenses	Lower	Unlocks production percentage buffs and combat stats	Requires stable power, food, and water

To maximize efficiency, build resource facilities close to your Power Generator to minimize cabling overhead. Upgrade existing facilities to boost their hourly throughput rather than filling space with multiple low-level rooms.

Managing Survivors and Worker Assignments

Assigning workers to facilities based on their specific traits increases hourly output and prevents resource bottlenecks.

Match Survivor Traits: Check worker profiles before placing them in a room. Assign survivors with high technical proficiency to power facilities, and place workers with agricultural traits in food production zones.
Upgrade Sleeping Quarters: Ensure sleeping quarters are upgraded to match your total population. Exhausted survivors experience drops in production efficiency, and adequate beds allow workers to recover without stopping base operations.
Cap Population Growth: Do not recruit or accept new survivors until your shelter produces a stable surplus of food and water. Uncontrolled population growth depletes reserves faster than low-level facilities can replenish them.

Balancing Expansion and Resource Harvest

Every expansion action consumes time and locks up available workers. Assigning your entire workforce to clearing rubble leaves your base without operational resources, while dedicating all workers to harvesting leaves your shelter cramped and unoptimized.

Maintain a split-task approach: keep a dedicated portion of your workforce assigned to continuous resource collection at production rooms, and use your remaining available workers for rubble removal and room upgrades. Secure stable power and water first, expand food production second, and transition to defensive and research facilities only after basic survival resources are stable.