This page is timeless and should be accurate for any version of Foxhole.
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A large forward operating base. Players can spawn and stockpile items here.
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— In-game description
The Bunker Base (colloquially known as BoB or BB) is a Bunker modification that acts as a Forward Base and provides Infrastructure for nearby connected Bunker and Trench segments. It can be upgraded for additional health and resistance.
Must be part of a Bunker Network with at least 6 bunkers (any tier, any upgrade)
Not be adjacent to a bunker with a garrison modification.
Tier 2
The Tier 2 Bunker Base is built by upgrading a Tier 1 Bunker Base that has unlocked the Small Garrison upgrade with a Construction Vehicle and 100 Basic Materials. It needs be part of a Bunker Network with at least 6 bunkers (any tier, any upgrade).
Tier 3
The Tier 3 Bunker Base is built by upgrading a Tier 2 Bunker Base that has unlocked the Large Garrison and Concrete Structures upgrades with a Construction Vehicle and 25 Concrete Materials. It needs be part of a Bunker Network with at least 6 bunkers (any tier, any upgrade).
Concrete Settling:
It must dry off for 24 hours but is already usable while wet. The duration increases during Snow Storms and Rain Storms depending on their intensity (up to double with highest intensity).
While very sturdy when dry, it is vulnerable while still wet. The vulnerability depends on how wet the concrete is and functions as a damage multiplier. Wet concrete that's just been placed has a x10 damage multiplier compared to dry concrete. After 8 hours the damage multiplier is roughly x3, and x2 after 12 hours.
Structural Integrity
The Bunker Base modification decreases the Structural Integrity of its Bunker Network: greatly if Tier 1, significantly if Tier 2 or 3.
Destruction
It is immune to Friendly Fire but if it's not Tier 3 it can be flagged for "Disruptive Structure Placement" to remove the immunity (10 "votes" needed at Tier 1, 20 at Tier 2). Bunkers in the same Bunker Network are also immune.
Reconstruction
When destroyed, the Bunker Base leaves behind a "husk" that can be destroyed or rebuilt. Reconstruction uses the same tool and materials as the current tier's construction.
If the faction which previously owned the base rebuilds it then it regains all the Stockpile and every Base Upgrades that were unlocked. But if the enemy faction captures it by rebuilding it then the base keeps 25% of its stock (none of the Soldier Supplies or Maintenance Supplies) and loses all its base upgrades.
Base Upgrades
Base Upgrades are additional functionalities that the base can unlock. They are slowly and automatically unlocked over time. Upgrades progress faster the more people assign their spawn to that base. A particular upgrade can be prioritized by voting for it in the menu of the Base if you've assigned your spawn there. Progression is sped up by things like supplying the base and building structures. You can remotely check the base upgrades unlocked or their progress at a given Base by hovering your mouse over its icon on the map.
Bunker Bases have two unique upgrades trees ("Garrison" and "Command") to unlock bunker specific upgrades. Those bunker upgrades also require Infrastructure, which is provided by building Infrastructure Modifications in Bunkers connected to the base by Trenches and Bunker (up to a max range of 40 pieces). There are two types of Infrastructure: "Garrison" and "Command" , one for each upgrade tree.
Image
Name
Required Infrastructure Modifications
Description
Unlock Time* "Friendly" Territory
Unlock Time* "Neutral/Enemy" Territory
"Base" Tree
Provisional Garrison
A Provisional Garrison connects the base to nearby defensive structures (80m radius). Defensive structures will deactivate if player activity (set spawn) is too low (<10).
25min
80min
Small Garrison
A small Garrison permanently connects the base to nearby defensive structures (80m radius).
Required to upgrade Base to Tier 2.
16hrs
43hrs
Large Garrison
A large Garrison permanently connects the base to nearby defensive structures (80m radius).
*Unlock Times listed here are approximate values and correspond to a Base's passive unlock time: zero player spawns assigned, 5+ friendly structures in range, 800+ Salvage (or equivalent value) in stockpile. Unlock times can be much shorter if many player spawns are assigned.
Use
Bunker Access
It has a built-in ramp that gives players access to the bunker network interior, similar to a Bunker Ramp.
At Tier 3 it gains a ladder that gives infantry access to its rooftop.
It provides Garrison to all friendly structures in a 80m radius if it has unlocked the Small Garrison upgrade, or if it has the Provisional Garrison upgrade and at least 10 players have their spawn assigned there.
Deployment Point
If it has unlocked the Deployment Point upgrade, players can deploy to it from the Home Region
Decay Prevention
If it has unlocked the Small Garrison upgrade, it can prevent the decay of player built structures in a 80m radius by consuming Maintenance Supplies from its stockpile.
Bunker&Trench Connections
Every Trench and Bunker physically connected to a Bunker Base form a network. The network start at the Bunker Base and reaches every connected bunker and trench for which the shortest connection to the bunker base is a chain of 40 trench/bunkers or less (including themselves and the bunker base). Trench husks and Bunker husks also count as valid connection for the network. The following effects are spread throughout this network:
Faction Ownership: Bunkers and Trenches in the network cannot be modified by the opposing faction.
Base Upgrades: Base Upgrades unlocked by the Bunker Base apply throughout the network. They allow connected Bunkers to be modified into the various bunker garrisons unlocked. Once a bunker has been modified into a bunker garrison it won't lose its modification if it's disconnected from the network.
Infrastructure: Infrastructure Modifications installed in the network's bunkers count towards the infrastructure requirements to unlock certain Base Upgrades at the Bunker Base.
At Tier 1 it is immune to small arms fire but not to 12.7mm machine gun fire. It isn't particularly resistant againt heavy explosives and is vulnerable to Demolition damage.
With Tier 2 it becomes immune to 12.7mm.
With Tier 3 it become more resistant to most damage types except Demolition.
The husks of each Tier have much more health than their live counterpart (4000 Tier 1, 20000 Tier 2, 40000 Tier 3). They can be destroyed permanently to prevent the enemy faction from rebuilding it.
Tips
Once an upgrade that required Infrastructure Modification is unlocked, removing those modifications won't make you lose the upgrade.
This is particularly useful if the builder only wants certain modifications, and doesn't want to deal with the increased maintenance cost
A destroyed Bunker Base can be rebuilt without the required 5 additional bunker pieces, allowing players to have a Bunker Base with no other bunker pieces attached to it
This is done by blueprinting the next tier Bunker Base, then demolishing the previously connected Bunkers while still in their grace period, and only then, completing the Bunker Base blueprint. This must be for each Bunker Base upgrade.
With equipment and materials on site, it will take a single player 11 minutes 49 seconds to dig and hammer (with the Construction Vehicle) the minimal requirements for a Bunker Base. Rounded up to an even 12 minutes to account for placing the blueprints, walk between dig sites, and entering/positioning the CV
upgrade with a Construction Vehicle and 100 Basic Materials. It needs be part of a Bunker Network with at least 6 bunkers (any tier, any upgrade).
and Concrete Structures 
upgrades with a Construction Vehicle and 25 Concrete Materials. It needs be part of a Bunker Network with at least 6 bunkers (any tier, any upgrade).
to remove the immunity (10 "votes" needed at Tier 1, 20 at Tier 2). Bunkers in the same Bunker Network are also immune.
and "Command" 
, one for each upgrade tree.
upgrade and at least 10 players have their spawn assigned there.
upgrade, players can deploy to it from the Home Region
