Hearts of Iron 4 Wiki

Constructions are fixed assets that may be built in states or provinces that are constructed using civilian factories.

State buildings

These buildings are built on a state level. Control of state resources or buildings requires controlling provinces worth at least 50% of the VP of that state, even if that does not include the province where the building icon is located. Airbases will appear, but do not become usable, unless the player also controls the province containing the airbase.

Name Cost Maximum level Effect
  Infrastructure 3000 10 Increases supply and supply throughput. Increases the speed of land units. Resources output is increased by 10% per level. Increases construction speed of  shared buildings.
  Air base 1250 10 Bases and repairs air units. Each air base level can host 200 aircraft.
  Anti-air 2500 5 Damages attacking air units and reduces damage from bombing. See Air combat#State anti-air.
  Radar station 3375 6 (depends on technology) Detects enemy forces, especially incoming aircraft. Radars also help detect enemy ships at sea.

Shared buildings

Like state buildings, shared buildings are built on a state level; however, they share a limited number of slots. This is perhaps the most important category of constructions, since it contains the factories necessary for production. Refineries have a hard cap of up to 3 refineries per state.

Name Base Cost Maximum level Effect
  Civilian factory 10800 20 Produces consumer goods and constructions, or can be used for trade. Base output is 5 (per day).
  Military factory 7200 20 Produces equipment (includes weapons, planes, vehicles). Base output is 4.5 (per day).
  Synthetic refinery 14500 3 Produces fuel 48-168 and  1-5 (Depends on Technology).
  Fuel silo 5000 3 Stores fuel (+100 000 per silo).
  Rocket site 6400 2 Produces (and can launch) one rocket per day. Rockets are also known as guided missiles.
  Nuclear reactor 30000 1 Produces nuclear bombs.

Infrastructure effects

Construction speed of shared buildings depends on the level of infrastructure in the state. Construction speed is multiplied by


Where the INFRA_MAX_CONSTRUCTION_COST_EFFECT in common/defines defaults to 1, and Maximum Infrastructure Level defaults to 10 in common/buildings.

So for example ×1.5 at 5/10 infrastructure. This bonus is applied after bonuses from tech, advisors, and national spirits, making 1 level of infrastructure a more powerful bonus than e.g. a War Industrialist. This encourages players to concentrate industry in central, high-infrastructure areas, although this must be balanced against the increased vulnerability of having all of one's industry in one place.

It is generally not economical to build more infrastructure solely for the purpose of increasing construction speed. Infrastructure is a relatively better deal in states with many empty slots; when planning to build civilian factories, refineries or reactors as they cost more; and at the start with countries with bad economy laws like the USA, as infrastructure construction isn't penalized like factory construction is.

Infrastructure provides diminishing returns to build times. Changing a province's infrastructure from 0 to 1 would require 5 military factories or 3 civilian factories to break even, 1 to 2 is 6 military or 4 civilian, all the way up to 9 to 10 which requires 16 military or 11 civilian.

The total amount of resources can also be increased by building infrastructure. Each level of infrastructure gives a resource increase to the total of all extracted resources in a state. The increase varies with both the starting quantity of resources and starting level of infrastructure.


It is possible to deconstruct shared buildings from the state tab by hovering over the building icon and pressing the X that appears in the lower right corner of the icon. During wartime, each state can only deconstruct one building per 30 days.

Slot count

Each state has a category, which then decides the base number of shared slots. Various technologies give percentage bonuses to how many slots a state can have. Various National Focuses may give additional bonus slots. The total number of slots is capped at 25.

Building slots.
Category Default number of slots Name in source files Example State
Megalopolis Region 12 megalopolis Greater London Area
Metropolis Region 10 metropolis New England
Dense Urban Region 8 large_city Southern Ontario
Urban Region 6 city Svealand
Sparse Urban Region 5 large_town Nebraska
Developed Rural Region 4 town Sardinia
Rural Region 2 rural Crete
Pastoral Region 1 pastoral Hejaz
Small Island 1 small_island Iwo Jima
Enclave 0 enclave Gibraltar
Tiny Island 0 tiny_island Midway Island
Wasteland 0 wasteland Libyan Desert

Province buildings

These buildings are built on a province level.

Name Cost Maximum level Effect
 Land fort 500 + (500 * Existing Local Land Fort Level) 10 Inflicts an attack penalty of -15% for each fort level on the attacker in combat. Attacking from multiple directions will reduce forts effect.
 Coastal fort 500 + (500 * Existing Local Coastal Fort Level) 10 Inflicts an attack penalty of -15% for each fort level on the attacker in naval invasion and 'strait crossing' combat.

Civilian factories

Civilian factories make all the improvements to a territory and are necessary to build any of the constructions listed under the “Constructions” tab. All nations start with a certain number of civilian factories and a percentage will be used for consumer goods, depending on the economy law and national spirits that are currently in place.

Civilian factories that are not used to produce consumer goods can be used for trade or to complete or repair the construction queued in the “Constructions” tab. It's possible to increase the number of civilian factories by building more, but this is limited by the number of  shared buildings slots available in each state.

Consumer goods

Depending on economic laws and national spirits, a number of civilian factories will be occupied by producing consumer goods and are unavailable for construction or trade. This number is computed as a percentage of the total number of factories, rounding upwards. Factories are counted even when they are damaged and can't produce anything.

  Universal Country Specific
-10%   Australian national spirit  Invest in Victory (from focus Squash the Squander Bugs)
+10%  Total Mobilization as economy law   Canadian national spirit  Great Depression (from focus Canada Wheat Board)
+15%   Australian national spirit  Great Depression (from focus National Security Act)
+20%  War Economy as economy law   Australian national spirit  Great Depression (present at start)
+25%  Partial Mobilization as economy law   Canadian national spirit  Great Depression (present at start)
+30%  Early Mobilization as economy law   United States national spirit  The Great Depression (present at start)
+35%  Civilian Economy as economy law  Isolation as economy law (  United States only, from focus Prepare Intervention)
+50%  Undisturbed Isolation as economy law (  United States only)

  South Africa can gain -3% consumer goods at  Total Mobilization with its spirits, but will not gain additional factories by this.


Suppose the civilian economy law is enabled (requiring 30% of civilian and military factories dedicated to consumer goods) and no other modifiers apply. A country has 50 military factories, 50 civilian ones and 20 Dockyards. It will then have 30 (civilian) factories dedicated to consumer goods.


The Factory Output of each civilian factory employed in construction is 5 per day. Construction Speed modifies the output for the building of all constructions.

  Universal Country Specific
+15%  Free Trade as trade law
+5%  Limited Exports as trade law
−10%  Service by Requirement as conscription law
−30%  All Adults Serve as conscription law
−40%  Scraping the Barrel as conscription law

There are also modifiers which only affect a single type of building. These are, primarily, the political advisors (Captain of Industry, Fortification Engineer, Quartermaster General and War Industrialist) but can also be one of many other national spirits activated by national focuses or events.

Efficiency of additional Civilian Factories

The return on investment of building an additional Civilian Factory will depend on the Construction Speed bonus as well the Economy Law currently in place, or expected in the future. The higher the Construction Speed bonus is, the more Output will be done by the newly built Civilian Factory and the faster it will accumulate an Output equal to its cost, 10800. This variable is the time, in days, required to recover the cost of building the factory, or payback time. The Economy Law will dictate what ratio of Civilian Factories are used for Consumer Goods and Output/Trade. The higher this ratio is, the longer the payback time of the newly built Civilian Factory will be. The payback time of a new Civilian Factory is given by the following formula:


The construction speed modifiers range between -70% and +65% and except for the lowest two modifiers, they all have multiple combinations to be achieved. In fact, there are 320 possible combinations of variables affecting Civilian Factory construction speed outside of national spirits and unique laws.

Minimum 0% Maximum
Undisturbed Isolation 8000 2400 2087
Isolation 5539 2216 1773
Civilian Economy 4115 2058 1524
Early Mobilization 2743 1920 1239
Partial Mobilization 2250 1800 1091
War Economy 2218 1695 1027
Total Mobilization 2000 1600 970

Minimal Construction Speed is -70% for Undisturbed Isolation and goes up to -20% with Partial Mobilization. Maximum Speed is 15% for Undisturbed Isolation and 65% with Partial Mobilization. All Values are rounded up to full days.

Additionally, because it's possible to assign up to 15 Civilian Factories (when available) to the construction of a new Civilian Factory, the number of days it will take to build a new one is given by the following formula:


Factory conversion

Civilian Factories can be converted into Military Factories for 4000 and Military Factories can be converted into Civilian Factories for 9000. These base cost is modified by several national spirits and political advisors. To convert a factory simply click on the corresponding state, and hover over the factory that shall be converted. The game will ask for confirmation. After confirmation the conversion now appears in the construction tab, just like any other building project.

Damage and repair

Each building level has 100 HP. They may get damaged by port strikes (naval bases), land combat (infrastructure, forts), resistance (factories), strategic bombing, or explicit events (like the Soviet Union's decision to move factories to the Urals). Nuclear bombs can destroy multiple or all levels of a building at once, for details see Nuclear_bomb#Effects.

The damage from land combat (against infrastructure) and strategic bombing gets scaled by the building's damage factor (air base and radar: 0.5, anti-air: 0.1, 1 otherwise) and the squared ratio of the currently undamaged building levels to the maximum level. For example, a level-3 anti-air building (maximum level 5) where one level is already partially damaged only receives   of incoming damage from strategic bombing. A single military factory in a state (or in other words a level-1 military factory) receives   while 15 military factories receive  . High-level factories and infrastructure will generally get damaged much more quickly from these two damage sources than lower levels.

State anti-air tooltip showing different bombing damage reductions for factories and other buildings.

Anti-air provides damage resistance from bomber-type attacks (port strikes and strategic bombing) depending on the level of anti-air in the containing state and researched anti-air technologies. Dispersed Industry provides an alternative source of damage resistance but only for factories and not stacking with anti-air. The maximum of the two is used for factories.

All damaged buildings appear in the construction list. The speed of factories assigned to a repair line gets a bonus of +100% plus any Factory Repair Speed bonuses (e.g. from Construction technologies and Construction Repair continuous focus). Even when no factories are assigned, the speed of the line is 0.3[2].

The resulting daily repair progress is  , rounded to the nearest full percent. So when assigning no factories, repairs will still progress by 1% per day. Assigning just a few factories to repair an expensive building may also produce just 1% progress per day, effectively wasting the factory output.

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  1. Local ship repair limitationsforum:1119095
  2. This is not increased by the Construction Repair continuous focus forum:1251943