Effect · every source

How to increase Additional fort level in CK3

9 sources raise Additional fort level and 0 lower it in the game files of patch 1.20.0.3.

additional_fort_level

The biggest boosts

+6MarchesBuilding · Each de jure county of the duchy
+6Siege WorksBuilding · Each de jure county of the duchy
+6Great BarracksBuilding · Each de jure county of the duchy

What raises Additional fort level (9)

Lifestyle perks (3)

Defender of the Faith+1
Theocracy governments
defender_of_the_faith_perk · game/common/lifestyle_perks/00_learning_3_theology_tree_perks.txt
Enduring Hardships+1
Not Adventurer government
enduring_hardships_perk · game/common/lifestyle_perks/00_martial_2_authority_tree_perks.txt
On the Road+1
Not Adventurer government
defensive_measures_perk · game/common/lifestyle_perks/00_stewardship_2_domain_tree_perks.txt

Buildings (6)

Marches+6
Each de jure county of the duchy
Levels 1–3: +2 to +6 (3 levels give it)
march · game/common/buildings/00_duchy_capital_buildings.txt
Siege Works+6
Each de jure county of the duchy
Levels 1–3: +2 to +6 (3 levels give it)
siege-works · game/common/buildings/00_duchy_capital_buildings.txt
Great Barracks+6
Each de jure county of the duchy
celestial-great-barracks · game/common/buildings/tgp_great_project_buildings.txt
Castle+4
Province · culture with Hidden Cities, in Jungle
Levels 1–4: +1 to +4 (4 levels give it)
castle · game/common/buildings/00_castle_buildings.txt
Tribal Hold+4
Province · culture with Hidden Cities, in Jungle
Levels 1–2: +2 to +4 (2 levels give it)
tribe · game/common/buildings/00_tribal_buildings.txt
Temple Citadel+4
Province · culture with Hidden Cities, in Jungle
Levels 1–4: +1 to +4 (4 levels give it)
temple-citadel · game/common/buildings/temple_citadel_buildings.txt

Source: game/common/buildings/00_castle_buildings.txt, game/common/buildings/00_duchy_capital_buildings.txt, game/common/buildings/00_tribal_buildings.txt, game/common/buildings/temple_citadel_buildings.txt, game/common/buildings/tgp_great_project_buildings.txt, game/common/lifestyle_perks/00_learning_3_theology_tree_perks.txt, game/common/lifestyle_perks/00_martial_2_authority_tree_perks.txt, game/common/lifestyle_perks/00_stewardship_2_domain_tree_perks.txt and the English localisation, Crusader Kings III 1.20.0.3. Building chains are shown once, at their strongest level, with the range over their levels. Effects that come only from events or scale with a script value are not listed.