Last Z: Survival Shooter Building Upgrade Priority Guide

In Last Z: Survival Shooter, focus your builder queues and construction materials directly on your Headquarters (HQ) and its direct prerequisites before leveling minor base infrastructure. Keeping your HQ, defensive Wall, and Research Center at maximum capacity unlocks higher troop tiers, vital combat buffs, and expanded march sizes faster than balancing every building evenly.

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Upgrade Priority Tiers

Base development relies on opening bottlenecks rather than upgrading every structure to the same level. Use the following hierarchy to decide where to invest your builders:

Building Category	Priority Level	Strategic Function
Headquarters & Wall	Highest	Dictates base level cap, unlocks features, and gates troop tiers.
Research Center	High	Prevents technology bottlenecks and unlocks advanced unit trees.
Barracks / Training Grounds	High	Increases unit tier quality, training capacity, and military power.
Hospitals / Medical Stations	Medium	Expands wounded capacity to prevent permanent troop death.
Resource Depots / Vaults	Situational	Upgraded only when resource caps block an upcoming HQ build.
Resource Production Fields	Low	Upgraded strictly when required as a prerequisite for the HQ or Wall.

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Step 1: Rush Headquarters and Required Prerequisites

Your Headquarters determines the maximum level of every other facility on your base. Delaying an HQ upgrade to level low-yield resource plots slows down your progression toward high-tier units and event rewards.

Check upcoming prerequisites: Before your current HQ construction finishes, inspect the requirements for the subsequent HQ tier. Upgrades routinely require a max-level defensive Wall alongside an alternating secondary building, such as a specific Barracks or the Research Center.
Pre-upgrade prerequisites: Assign your builders to complete required sub-structures ahead of time so your HQ can begin upgrading as soon as the previous tier completes.
Avoid cosmetic leveling: Do not pause HQ progression to raise secondary buildings that do not directly unlock the next command tier or boost immediate combat strength.

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Step 2: Keep the Research Center Aligned with HQ

Technology research timers represent one of the longest progression gates in the game. An underleveled Research Center (Tech Institute) prevents you from starting high-tier economic and military projects.

Tree Unlocks: Advanced combat and development trees require specific Research Center levels before they become accessible.
Unit Milestones: High-tier combat units, such as Tier 9 and Tier 10 troops, sit behind deep research requirements that demand an up-to-date science facility.
Queue Uptime: Upgrade your Research Center immediately after your HQ finishes so your science queue never sits idle waiting on structural prerequisites.

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Step 3: Maintain Military and Medical Readiness

Once your HQ prerequisites and science facilities are under construction, direct your remaining builder time into military infrastructure.

Barracks (Training Grounds)

Upgrading your Barracks raises the tier of soldiers you can recruit and increases batch training size. High-tier troops improve your performance in player-versus-environment (PvE) exploration stages, daily events, and territorial defense.

Hospitals (Medical Stations)

Combat outside safe gathering areas sends wounded troops to your Hospital. If your wounded count exceeds total Hospital capacity, all overflow units die permanently. Keep medical capacity high enough to accommodate your primary march and base garrison before entering active combat zones.

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Step 4: Manage Depots and Passive Production Fields

Passive resource generators—including farms, timber yards, and iron mines—yield a small trickle of materials compared to active map gathering, daily event crates, and combat rewards.

Resource Depots (Vaults): Upgrade storage structures only when your current storage ceiling prevents you from holding the raw resources required to start an HQ upgrade.
Resource Fields: Leave passive generators at the minimum level required to satisfy HQ prerequisite chains. Diverting builder time to resource fields yields low returns and delays crucial combat milestones.

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Reducing Construction Timers

Before confirming multi-day structural upgrades on your HQ or defensive Wall, reduce the timer with available modifiers:

Alliance Help: Join an active alliance so teammate assists reduce construction timers immediately after you begin building.
Economic Research: Invest skill points into construction speed nodes within your settlement's development tech tree early.
Queue Distribution: If a second builder queue is available, assign your primary builder to long-term anchors like the HQ and Wall while using the secondary queue to clear short prerequisites and depot upgrades.