effect · add_building_construction

Hands-On Usage

add_building_construction is commonly used in events, decisions, or focus completions to queue a building construction in a state immediately, rather than instantly completing the building and bypassing the construction queue. This is suitable for simulating the procedural feel of "national investment launching projects." For example, in an industrial aid decision, you can queue the construction of a factory in a target state:

# Execute within STATE scope (e.g., already scoped to the target state in an event option)
add_building_construction = {
    type = industrial_complex
    level = 2
    instant_build = no
}

Synergy

• [free_building_slots](/wiki/trigger/free_building_slots) — Check before execution whether the state still has available building slots, preventing logic errors caused by insufficient slots preventing construction from starting.
• [add_extra_state_shared_building_slots](/wiki/effect/add_extra_state_shared_building_slots) — When slots are insufficient, expand shared slots first, then immediately call this effect to begin construction, forming a standard "expand slots → build" combination.
• [can_construct_building](/wiki/trigger/can_construct_building) — Use as a prerequisite trigger to verify that the state meets all construction conditions for the building (technology, resources, terrain restrictions, etc.), preventing silent script failures.
• [set_building_level](/wiki/effect/set_building_level) — If you need to instantly complete the building and bypass the construction queue, use this effect instead; the two are mutually substitutable, choose based on whether you need the "construction process."

Common Pitfalls

1. Forgetting the meaning of the instant_build field: When omitted or set to no, the construction enters the normal construction queue and is affected by the number of civilian factories. Many newcomers mistakenly believe the effect didn't work, when in reality construction is still in progress; if you want immediate results during testing, you must explicitly write instant_build = yes, but overusing this field in official mods will break game balance.
2. Calling directly outside STATE scope: This effect only works within STATE scope. If you forget to switch scope using capital_scope or a specific state variable in a focus's complete_effect under COUNTRY scope and call it directly, the game won't report an error but the construction won't be created, making it extremely difficult to debug.