Last Fortress: Underground Shelter Expansion and Facility Guide

To expand your shelter efficiently in Last Fortress: Underground, assign your available survivors to clear rubble from blocked rooms immediately. Removing debris unlocks space tiles for essential utility facilities—such as power generators and cafeterias—which maintain resource flow and support base infrastructure.

Priority Step: Clear Rubble to Unlock Facilities

Every blocked room limits your shelter's growth. Removing debris must take priority over non-essential construction because cleared rooms provide the physical tiles needed for new installations.

Assign Maximum Labor: Send your idle workers directly to rubble piles to keep excavation times short.
Build Immediately After Clearing: Construct utility buildings—specifically power generators for electricity and cafeterias for food—as soon as a room is clear so that space is not left unutilized.
Keep Resource Stations Manned: Shift workers from finished excavation projects directly into production facilities to maintain stable resource gains.

Managing Worker Assignments and Production

Survivor labor keeps resource production consistent. Interacting with room interfaces allows you to adjust staff based on immediate shelter demands.

Production Shifts: If food or electricity reserves fall low, temporarily reassign workers from debris excavation to active production stations.
Population Monitoring: Ensure your total survivor count is high enough to run newly built facilities without leaving key infrastructure unstaffed.
Layout Efficiency: Group high-traffic rooms, such as power plants and cafeterias, near active work zones to streamline task transitions.

When to Upgrade Facilities vs. Clear Space

Managing room upgrades alongside space clearing prevents bottlenecking your shelter's growth:

Action	When to Prioritize	Primary Benefit
Room Excavation	Early progression or when new facility slots are needed	Expands total base layout and enables new building types
Facility Upgrades	When room space is exhausted or storage caps are hit	Boosts resource output per cycle and increases storage capacity

Upgrade power generators and cafeterias whenever resource demands increase. If your material storage hits its maximum cap, invest resources into storage facility upgrades before continuing further excavation.

Target Progression Milestones

Focus your expansion efforts on rooms tied to major game mechanics rather than cosmetic spaces:

Follow Objective Tasks: Complete the game's recommended room expansions to maintain steady progress toward key shelter capabilities.
Target Key Infrastructure: Prioritize unlocking rooms designated for the Command Center and research stations, as these facilities provide research bonuses and enhance shelter survival.