Construction

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	6000	5	Increases supply and supply throughput. Increases the movement speed of land units. Affects the organization recovery rate of land units. Resources output is increased by +20% 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 state anti-air.
	Radar station	3375	6 (depends on technology)	Detects enemy forces, especially incoming aircraft. Radars also help detect enemy ships at sea and can increase intelligence in other nations.

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, or can be used to create and upgrade intelligence agencies. Base output is 5 (per day).
	Military factory	7200	20	Produces equipment (includes weapons, planes, vehicles). Base output is 4.50 (per day).
	Naval dockyard	6400	20	Produces and repairs ships. Base output is 2.5 (per day).
	Synthetic refinery	14500	3	Produces 48-168 fuel 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 per site. Max storage capacity is 100 rockets per rocket site level. Therefore a level 2 rocket site has a maximum capacity of 200 rockets. Rockets are also known as guided missiles.
	Nuclear reactor	30000	1	Produces nuclear bombs at a rate of 1 per year (365 days).

Infrastructure effects

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

$1+{\bigg (}{\text{State infrastructure}}\cdot {\frac {\text{Max Infrastructure Construction Cost Effect}}{\text{State Infrastructure Max Level}}}{\bigg )}$

Where the INFRA_MAX_CONSTRUCTION_COST_EFFECT in /Hearts of Iron IV/common/defines/00_defines.lua defaults to 1, and Maximum Infrastructure Level defaults to 5 in /Hearts of Iron IV/common/buildings/00_buildings.txt.

So for example ×1.6 at 3/5 infrastructure. In the Construction UI, this bonus is displayed for each State as a colored percentage next to an Infrastructure road icon. 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.

Given the above formula and values and the lost production points from forgone civilian factories during the time of infrastructure production (uncompounded opportunity cost), the following table shows the minimum number of open slots for civilian factories to break even on the increased cost of infrastructure. One might infer that it is rarely advantageous to add more than two levels of infrastructure for construction speed alone.

Minimum slots open to fill with Civilian Factory for start Infrastructure

End	Start at 0	Start at 1	Start at 2	Start at 3	Start at 4
1	4
2	7	4
3	12	8	5
4	16	13	9	5
5	22	18	15	10	6

Note that the returns don't diminish as much as one might expect because of reduced opportunity cost (days of lost infrastructure production from fractional factories) when moving from higher versus lower starting infrastructure and producing civilian factories. Returns for construction other than civilian factories diminish faster because other infrastructure does not return production points and, thus, has no opportunity cost beyond the break-even level. For example, a close approximation of the break-even number of open slots for military factories is the number in the table * (1.125 + (0.05 * end_infrastructure_level)).

The total amount of resources can also be increased by building infrastructure. Each level of infrastructure gives a resource increase of +20% to the total of all extracted resources (except those resources produced by a synthetic refinery or resources acquired via trade) in a state. There are five (5) levels of infrastructure; building all of them will give a +100% bonus to the extracted resources total.

The infrastructure level also affects land unit organization recovery rates per the following table:

Infrastructure level	5	4	3	2	1
Organization recovery rate	+25%	+15%	+5%	-5%	-15%

Once a state's Infrastructure reaches maximum (level 5), a building slot can be added to that state using a Decision called “Region-wide Industrial Integration” that costs 100 PP.

Diminishing Returns

Infrastructure provides diminishing returns to build times.

Note: this is now out of date for the current version which has 5 levels of Infrastructure instead of 10.

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.

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.

Reconstructing

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	Madagascar
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. Unlike state or shared buildings, these buildings benefit whoever controls the province they are in regardless of overall control of the state.

	Name	Cost	Maximum level	Effect
	Naval base	5000 + 1000 * current level	10	Stations naval fleets, and can send and receive supplies and resources via convoys. Each naval base level increases supply capacity, supply throughput and the number of local ship repairs.
	Land fort	500 + 500 * current 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 * current level	10	Inflicts an attack penalty of -15% for each fort level on the attacker in naval invasion and 'strait crossing' combat.
	Railway	170 + 130 * current level	5	Transports supplies from the capital to supply sources like cities, ports or supply hubs.
	Supply hub	20000	1	Distributes supplies from railways.

Civilian factories

Civilian factories make all the improvements to a territory and are necessary to build any of the constructions listed under the Construction 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 Construction 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, national spirits and stability, 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, including military factories and factories received by trade. Factories are counted even when they are damaged and can't produce anything. The number of consumer goods factories is always rounded down.

	Universal	Country-specific
−20%		German national spirit  Rebuild the Nation for 365 days
−15%		Communist Chinese national spirit  Permit Opium Trade Chinese Warlord national spirit  Embrace the Opium Trade
−10%		Australian national spirit  Invest in Victory  Chinese national spirit Grain Tax (from focus Grain Tax) Chinese Warlord national spirit War Taxes (from focus War Taxes)  Greek national spirit  Schachtplan (present at start)  Nationalist Spanish national spirit National Recovery (from focus Spanish Austerity)  Turkish national spirit İnanç Vergısı (from focus İnanç Vergısı)
−9%		Anarchist Spanish national spirit Anarchist Society (from focus Communal Autarky)
−8%		Canadian national spirit  War Bonds (from focus If Day)  South African national spirit  Cheap Labor (from focus Outlaw Strikes)
−7%		Bulgarian national spirit Government Reforms (from focus Corporatism)  Turkish national spirit Etatism (from focus Continue the Policy of Etatism)  Turkish national spirit Reappropriated Exploitive Finance (from focus Scraping Our Debts)
−6%		Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States if 5 countries get guaranteed)  Anarchist Spanish national spirit Anarchist Society (from focus Agrarian Collectivization)
−5%	Having 100% stability (−1% from each 10% of stability over 50%)	Albanian national spirit Balkan Trade Union Secretariat (from Bulgarian focus Balkan Trade Union Secretariat if they’re in a faction with Bulgaria)  Australian national spirit  Invest in Victory  Bulgarian national spirit Tobacco Exports (from focus Expand the Tobacco Industry)  Bulgarian national spirit Government Reforms (from either focus Collectivization of the Countryside or Agrarian Cooperative Movement)  Bulgarian national spirit Balkan Trade Union Secretariat (from focus Balkan Trade Union Secretariat)  Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States if 4 countries get guaranteed)  Bulgarian national spirit Foreign Industry (from focus Appeal to European Capitalists) Chinese Warlord national spirit Land Value Tax (from focus Land Value Tax)  Czechoslovak national spirit Arms Exports (from focus Export Subsidies)  Czechoslovak national spirit Extensive Arms Exports (from focus Equal Access Guarantee)  French national spirit Devalue the Franc (from focus Devalue the Franc)  Greek national spirit  Command Economy  Greek national spirit Collectivized Agriculture (from focus Agricultural Communes)  Greek national spirit Metaxism (from focus An Orthodox State)  Greek national spirit Schachtplan (from focus Bolster the Schachtplan)  Greek national spirit Farmer-Focused Culture (from focus Utilize Our Strengths)  Greek national spirit Balkan Trade Union Secretariat (from Bulgarian focus Balkan Trade Union Secretariat if they’re in a faction with Bulgaria)  Greek national spirit The Central Balkan Bank of Athens (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey and Greece has completed the focus The Bedrock of Balkan Financial Stability)  German national spirit  Mefo Bills (present at start)  German national spirit Prepare for the Next Blockade (from focus Prepare for the Next Blockade)  Hungarian national spirit Intervention (from focus Economic Intervention)  Republican Spanish national spirit Seized Gold Reserves (from focus Seize the Gold Reserves)  Republican Spanish national spirit Wealth Redistribution (from focus Wealth Redistribution)  Republican Spanish national spirit Class War (from focus All Must Do Their Part)  Republican Spanish national spirit Appropriate Church Riches (from focus Appropriate Church Riches)  Republican Spanish national spirit Relocate the Gold Reserves (from focus Relocate the Gold Reserves)  Republican Spanish national spirit Provide for the People (from focus Provide for the People)  Romanian national spirit Agrarian Reform (from focus Agrarian Reform)  Romanian national spirit Balkan Trade Union Secretariat (from Bulgarian focus Balkan Trade Union Secretariat if they’re in a faction with Bulgaria)  Romanian national spirit The Central Balkan Bank of Athens (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey and Greece has completed the focus The Bedrock of Balkan Financial Stability)  Turkish national spirit Privatized Infrastructure (from focus Privatize Our Infrastructure)  Turkish national spirit Funkplan (from focus Approve the Funkplan)  Turkish national spirit Turkish Bolshevism (from focus Reconciling Kemalism with Bolshevism)  Turkish national spirit The Central Balkan Bank of Athens (from focus Create the Balkan Central Bank if Greece has completed the focus The Bedrock of Balkan Financial Stability)  Turkish national spirit Balkan Trade Union Secretariat (from Bulgarian focus Balkan Trade Union Secretariat if they’re in a faction with Bulgaria)  British national spirit  British Austerity  British national spirit  For the Good of the Revolution  United States national spirit Accumulated Wealth Tax Act (from focus Accumulated Wealth Tax Act)  Nationalist Spanish national spirit Regional Agrarian Commissions (from focus Regional Agrarian Commissions)  Nationalist Spanish national spirit National Recovery (from focus National Recovery)  Dutch national spirit Friesland Agricultural Impetus (from focus Friesland Agricultural Impetus)  New Zealand national spirit  Wairarapa Sheep Farms (from focus Wairarapa Sheep Farms)  South African national spirit  Gold Exports (from focus Expand the Rand Mines)  Soviet national spirit Yugoslavian Economic Aid (from Yugoslav focus Mutual Economic Aid)  Yugoslav national spirit Foreign Capital (from focus Attract Allied Capital)  Yugoslav national spirit Yugoslavian Economic Aid (from focus Mutual Economic Aid)  Yugoslav national spirit Balkan Trade Union Secretariat (from Bulgarian focus Balkan Trade Union Secretariat if they’re in a faction with Bulgaria)  Yugoslav national spirit The Central Balkan Bank of Athens (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey and Greece has completed the focus The Bedrock of Balkan Financial Stability)
−4%		Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States if 3 countries get guaranteed)
−3%		Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States if 2 countries get guaranteed)  Greek national spirit The Balkan Central Bank (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey)  Anarchist Spanish national spirit Anarchist Society (from focus Shared Burdens)  Romanian national spirit The Balkan Central Bank (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey)  South African national spirit  Cheap Labor (from focus Work for All Poor)  Turkish national spirit The Balkan Central Bank (from focus Create the Balkan Central Bank)  Yugoslav national spirit The Balkan Central Bank (from Turkish focus Create the Balkan Central Bank if they’re in a faction with Turkey)
−2%		Indian national spirit  Princely State Donations  Bulgarian national spirit National Industry (from focus Utmost Optimization)  Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States if 1 country gets guaranteed)  Bulgarian national spirit Government Reforms (from focus Industrial Autarky)  Canadian national spirit  War Bonds (from focus War Bonds)  New Zealand national spirit  First Labor Government  Portuguese national spirit Hydroelectric Power (from focus Hydroelectricity)  Portuguese national spirit Estado Novo (from focus Strengthen the Regime)
−1%		Bulgarian national spirit Our Duty in the Balkans (from focus Free Balkan States)  Portuguese national spirit Estado Novo (from focus Estado Novo)  Portuguese national spirit National Gold Reserves (from focus National Gold Reserves)
+2%		New Zealand national spirit  Waitangi Tribunal (from focus Waitangi Tribunal)
+3%		Romanian national spirit Royal Household Accounts (gained by event)
+4%		Bulgarian national spirit National Industry (from focus Invigorate National Industry)
+5%		Australian national spirit  Great Depression  French national spirit Matignon Agreements (from focus Reform the Labour Laws)  Indian national spirit  Famine (gained by event)  Chinese national spirit Low Inflation (present at start)  Greek national spirit Foreign Monopolies (from either focus Encourage Tourism or Mobilize Our Economy)  Greek national spirit Small Debt Repayment (from decision)  Japanese national spirit Zaibatsus (present at start)
+8%		Bulgarian national spirit National Industry (from focus Increase Industry Investments)
+10%	Total Mobilization as economy law	Canadian national spirit  Great Depression (from focus Canada Wheat Board)  Chinese national spirit Moderate Inflation (from a focus that increases inflation)  Greek national spirit Foreign Monopolies (from either focus Expand Our Tobacco Industry or Increase Our Mining Operations)  Spanish national spirit Recovering From Civil War (at the end of the Spanish Civil War)
+15%		Australian national spirit  Great Depression  Chinese national spirit Heavy Inflation (from a focus that increases inflation)  Greek national spirit Debt to the I.F.C (present at start)  Greek national spirit Foreign Monopolies (from either focus Exporting More Luxury Commodities or Greek Autarky)  Greek national spirit Large Debt Repayment (from decision)  Romanian, national spirit King Carol Emptied Accounts (from focus Forced Abdication)  Collectivized Society as economy law ( Regional Defense Council of Aragón only, from focus All Must Bear the Torch)
+17.5		United States national spirit Slow Economic Growth (from a focus that reduces the effect of the Great Depression)
+20%	War Economy as economy law	Australian national spirit  Great Depression (present at start)  Chinese national spirit Hyper Inflation (from a focus that increases inflation)  Greek national spirit Foreign Monopolies (present at start)  Romanian national spirit Supplementary Budget (gained by event)
+25%	Partial Mobilization as economy law	Canadian national spirit  Great Depression (present at start)  Chinese national spirit Economic Collapse (from a focus that increases inflation)  Romanian national spirit Embezzlement Scandal (gained by event)  United States national spirit Slow Recovery (from a focus that reduces the effect of the Great Depression)
+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, present at 1939 start)
+50%		Undisturbed Isolation as economy law ( United States only, present at start)

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

Example

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.

Output

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
+10%	Export Focus as trade law  Construction I  Construction II  Construction III  Construction IV  Construction V	New Zealand national spirit  The Worker's Party  New Zealand national spirit  In the Darkness  Soviet national spirit  Worker's Culture
+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:

${\text{Payback Time}}={\frac {10800}{5\cdot (1+{\text{Construction Speed Bonus}})\cdot \left(1-{\frac {\text{Consumer Goods Factories}}{100}}\right)}}$

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.

	Economy Law	Construction Speed
		Minimum (-70%)	0%	Maximum (+65%)
Payback Time (Days)	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:

${\text{Build Time}}={\frac {10800}{\#{\text{Factories}}\cdot 5\cdot \left(1+{\frac {\text{SpeedBonus}}{100}}\right)}}$

Factory conversion

Civilian Factories can be converted into Military Factories for 4000. Military Factories can be converted into Civilian Factories for 9000. The 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 $\left(2/5\right)^{2}\cdot 0.1=1.6\%$ of incoming damage from strategic bombing.

A single military factory in a state (or in other words a level-1 military factory) receives $\left(1/20\right)^{2}=0.25\%$ while 15 military factories receive $\left(15/20\right)^{2}=56.25\%$. 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.

The resulting daily repair progress is ${\text{median}}(1\%,{\text{speed}}/{\text{building cost}}\cdot 100\%,100\%)$, 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.

Mechanics

Events and Decisions

Events • Decisions