upgrade_farm_building

upgrade_farm_building = {
	if = {
		limit = { 
			building_farm_estates_requirement_terrain = yes
		}
		if = {
			limit = {
				NOT = { has_building = farm_estates_01 }
				free_building_slots = 0
			}
			add_province_modifier = extra_building_slot
			add_building = farm_estates_01
		}
		else_if = {
			limit = {
				NOT = { has_building = farm_estates_01 }
				free_building_slots > 0
			}
			add_building = farm_estates_01
		}
		else_if = {
			limit = {
				has_building = farm_estates_01
			}
			add_building = farm_estates_02
		}
		else_if = {
			limit = {
				has_building = farm_estates_02
			}
			add_building = farm_estates_03
		}
		else_if = {
			limit = {
				has_building = farm_estates_03
			}
			add_building = farm_estates_04
		}
		else_if = {
			limit = {
				has_building = farm_estates_04
			}
			add_building = farm_estates_05
		}
		else_if = {
			limit = {
				has_building = farm_estates_05
			}
			add_building = farm_estates_06
		}
		else_if = {
			limit = {
				has_building = farm_estates_06
			}
			add_building = farm_estates_07
		}
		else_if = {
			limit = {
				has_building = farm_estates_07
			}
			add_building = farm_estates_08
		}
	}
	else = {
		if = {
			limit = {
				NOT = { has_building = pastures_01 }
				free_building_slots = 0
			}
			add_province_modifier = extra_building_slot
			add_building = pastures_01
		}
		else_if = {
			limit = {
				NOT = { has_building = pastures_01 }
				free_building_slots >= 0
			}
			add_building = pastures_01
		}
		else_if = {
			limit = {
				has_building = pastures_01
			}
			add_building = pastures_02
		}
		else_if = {
			limit = {
				has_building = pastures_02
			}
			add_building = pastures_03
		}
		else_if = {
			limit = {
				has_building = pastures_03
			}
			add_building = pastures_04
		}
		else_if = {
			limit = {
				has_building = pastures_04
			}
			add_building = pastures_05
		}
		else_if = {
			limit = {
				has_building = pastures_05
			}
			add_building = pastures_06
		}
		else_if = {
			limit = {
				has_building = pastures_06
			}
			add_building = pastures_07
		}
		else_if = {
			limit = {
				has_building = pastures_07
			}
			add_building = pastures_08

As written in game/common/scripted_effects/01_building_upgrade_effects.txt.