Construction

_{Focus Areas · Design document §3}

Available from: S03 (Quarrying)

22 breakthroughs — CORE 6 · STANDARD 6 · UNCOMMON 3 · RARE 2 · UNIQUE 5 — Primitive – Space

Builds on: Foraging (1) · Stonework (3) · Social Organization (2) · Mining (1) · Metallurgy (4) · Warfare (4) · Mathematics (4) · Philosophy and the Arts (1) · Textiles & Materials (1) · Mechanics (2) · Chemistry (1) · Computing (1) · Materials Science (1) · Space Engineering (1)

Leads into: Farming (2) · Mining (1) · Metallurgy (1) · Seafaring (3) · Warfare (3) · Philosophy and the Arts (1) · Water Management (4) · Electricity (1) · Quintessic Physics (1) · Rocketry (2) · Space Engineering (2)

_{The numbers count prerequisite links between this focus and the other. How to read the tables.}

Overview

ID	Breakthrough	Tier	Era	Prerequisites
CO01	Mud Brick Construction	CORE	Primitive	G02 (Seed Saving)
CO02	Post and Lintel	CORE	Ancient	S03
CO03	Arch Construction	CORE	Ancient	S03 + MA01 (Geometry)
CO04	Roman Concrete	STANDARD	Classical	CO03 + MI06B (Volcanic Ash)
CO05	Corbel Arch/Vault	STANDARD	Ancient	S03
CO06	Flying Buttress	STANDARD	Medieval	CO03 + MA03 (Basic Algebra — trigonometry)
CO07	Earthquake-Resistant Design	UNCOMMON	Classical	CO02 + Earthquake-prone region
CO08	Modular Construction	RARE	Ancient	CO01 + SO05 (Specialization)
CO09	Suspension Bridge	UNCOMMON	Medieval	CO03 + (ME05 (Steel) or TX01 (Weaving — rope-making))
CO10	Iron-Frame Construction	CORE	Early Modern	ME08 + CO03
CO11	Reinforced Concrete	STANDARD	Modern	(CO04 or CH05) + ME12 — Roman Concrete, or the chemistry of Portland cement; and Bessemer steel
CO13	Geodesic Structures	UNCOMMON	Atomic	CO11 + MA03 (Basic Algebra — trigonometry)
CO14	3D Printed Construction	RARE	Atomic	MC11 (Assembly Line — prefabrication) + CP01 (Computer) + MS01 (Composites)
CO15	Orbital Construction	STANDARD	Space	CO13 + SE02 (Orbital Assembly)
CO23	Railway Network	CORE	Early Modern	MC08 (Steam Engine) + CO03 (Arch Construction — roads) + ME08 (Blast Furnace)
CO18	Coral Architecture	UNIQUE	Ancient	CO01 + Coastal + Tropical biome
CO19	Crannog Lake Dwelling	UNIQUE	Ancient	CO01 + Lake/wetland terrain
CO20	Earthquake Mastery	UNIQUE	Classical	CO02 + Earthquake-prone region + MA01 (Geometry)
CO21	Ceremonial Road Network	UNIQUE	Classical	CO03 (Arch Construction — roads) + CU02 (Monumental Architecture) + Mountain or Jungle biome
CO22	Mound Builder Tradition	UNIQUE	Ancient	CO01 + SO03 (Tribal Law) + River + Grassland biome
CO24	Concentric Fortification	CORE	Medieval	WA06 (Fortification Design) + CO03 (Arch)
CO25	Star Fort	STANDARD	Early Modern	WA06 + (WA22 Cannons or WA11 Trebuchet)

Prerequisite map

flowchart LR
  n_CO01["CO01 Mud Brick Construction"]:::CORE
  n_CO08["CO08 Modular Construction"]:::RARE
  n_CO18["CO18 Coral Architecture"]:::UNIQUE
  n_CO19["CO19 Crannog Lake Dwelling"]:::UNIQUE
  n_CO22["CO22 Mound Builder Tradition"]:::UNIQUE
  n_CO02["CO02 Post and Lintel"]:::CORE
  n_CO07["CO07 Earthquake-Resistant Design"]:::UNCOMMON
  n_CO20["CO20 Earthquake Mastery"]:::UNIQUE
  n_CO03["CO03 Arch Construction"]:::CORE
  n_CO04["CO04 Roman Concrete"]:::STANDARD
  n_CO11["CO11 Reinforced Concrete"]:::STANDARD
  n_CO13["CO13 Geodesic Structures"]:::UNCOMMON
  n_CO15["CO15 Orbital Construction"]:::STANDARD
  n_CO06["CO06 Flying Buttress"]:::STANDARD
  n_CO09["CO09 Suspension Bridge"]:::UNCOMMON
  n_CO10["CO10 Iron-Frame Construction"]:::CORE
  n_CO23["CO23 Railway Network"]:::CORE
  n_CO21["CO21 Ceremonial Road Network"]:::UNIQUE
  n_CO24["CO24 Concentric Fortification"]:::CORE
  n_CO05["CO05 Corbel Arch/Vault"]:::STANDARD
  n_CO14["CO14 3D Printed Construction"]:::RARE
  n_CO25["CO25 Star Fort"]:::STANDARD
  n_CO03 --> n_CO04
  n_CO03 --> n_CO06
  n_CO02 --> n_CO07
  n_CO01 --> n_CO08
  n_CO03 --> n_CO09
  n_CO03 --> n_CO10
  n_CO04 -.-> n_CO11
  n_CO11 --> n_CO13
  n_CO13 --> n_CO15
  n_CO03 --> n_CO23
  n_CO01 --> n_CO18
  n_CO01 --> n_CO19
  n_CO02 --> n_CO20
  n_CO03 --> n_CO21
  n_CO01 --> n_CO22
  n_CO03 --> n_CO24
  classDef CORE fill:#dbeafe,stroke:#1d4ed8,color:#0b1b3b
  classDef STANDARD fill:#f1f5f9,stroke:#64748b,color:#0f172a
  classDef UNCOMMON fill:#dcfce7,stroke:#15803d,color:#052e16
  classDef RARE fill:#fef3c7,stroke:#b45309,color:#3b2005
  classDef UNIQUE fill:#fae8ff,stroke:#a21caf,color:#3b0a3f

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_{Prerequisites within this focus. Box colour is the tier (blue CORE, grey STANDARD, green UNCOMMON, amber RARE, purple UNIQUE); dotted arrows are alternatives (“or”); a line can pass behind another box, so follow it from its start. 19 of these 22 breakthroughs also need breakthroughs from other foci, which the overview above lists.}

Breakthroughs

CO01 · Mud Brick Construction

• Tier: CORE · Era: Primitive
• Prerequisites: G02 (Seed Saving)
• Unlocks: Granary. Sun-dried brick bound with the straw of the first harvests: the first permanent architecture.
• Leads to: FA15 Mountain Terrace Farming, MI05 Deep Shaft Mining, CO08 Modular Construction, CO18 Coral Architecture, CO19 Crannog Lake Dwelling, CO22 Mound Builder Tradition, WM10 Ice Architecture

CO02 · Post and Lintel

• Tier: CORE · Era: Ancient
• Prerequisites: S03
• Unlocks: Colosseum; Lumber mill (improvement); the Polynesian Moai.
• Leads to: ME08 Blast Furnace, CO07 Earthquake-Resistant Design, CO20 Earthquake Mastery, SF05 Trireme/Galley Construction, WA05 Siege Warfare, WA24 Fortified Border Tradition, CU02 Monumental Architecture

CO03 · Arch Construction

• Tier: CORE · Era: Ancient
• Prerequisites: S03 + MA01 (Geometry)
• Unlocks: Road (improvement — Road Building, merged here in v3.100: roads and their bridges together); ⟨Roads connect tiles across rivers⟩ (the canonical Engineering unique — bridges); ⟨[+5]% Production when constructing [All] buildings [in all cities]⟩ (the arch spans wider rooms). Prerequisite for the Aqueduct (WM02). Post Officeⁿ [55/1; +1 Gold; ⟨[+1 Gold] from each Trade Route⟩; ⟨[+25]% spy effectiveness [in this city]⟩ (<when espionage is enabled>)] — the post rides the roads: the Persian royal road, the Roman cursus publicus (Postal System, merged here in v3.102).
• Leads to: CO04 Roman Concrete, CO06 Flying Buttress, CO09 Suspension Bridge, CO10 Iron-Frame Construction, CO23 Railway Network, CO21 Ceremonial Road Network, CO24 Concentric Fortification, SF10 Drydock, WA06 Fortification Design, WM02 Aqueduct, WM11 Industrial Canal Network

CO04 · Roman Concrete

• Tier: STANDARD · Era: Classical
• Prerequisites: CO03 + MI06B (Volcanic Ash)
• Unlocks: Concrete Worksⁿ [40/0; cityHealth +25; ⟨[-10]% maintenance cost for [All] buildings [in this city]⟩ — seawater-proof harbours]. Lost for a millennium, in our world.
• Notes: Lost and not rediscovered for a millennium.
• Leads to: CO11 Reinforced Concrete

CO05 · Corbel Arch/Vault

• Tier: STANDARD · Era: Ancient
• Prerequisites: S03
• Unlocks: Corbel Vaultⁿ [30/0; cityStrength +3; ⟨[10]% Food is carried over after population increases [in this city]⟩ — cool undercrofts]. Competing Solution (§1.2): the alternative to Arch Construction (CO03), detour margin ×1.5 while Arch Construction exists in this world; if Arch Construction is discovered first this is never developed, and if it arrives later this is superseded. The Corbel Vault carries ⟨Unavailable <after discovering [Arch Construction]>⟩.
• Notes: Maya/Mycenaean approach.

CO06 · Flying Buttress

• Tier: STANDARD · Era: Medieval
• Prerequisites: CO03 + MA03 (Basic Algebra — trigonometry)
• Unlocks: ⟨[+15]% Production when constructing [University] buildings [in all cities]⟩ — the masons who raised the cathedrals raised the colleges. Notre Dame, Taj Mahal, Porcelain Tower (world wonders). Walls that lean on air.

CO07 · Earthquake-Resistant Design

• Tier: UNCOMMON · Era: Classical
• Prerequisites: CO02 + Earthquake-prone region
• Unlocks: Timber-Frame Hallⁿ [75/1; +2 Gold (the technique sells); ⟨[-25]% maintenance cost for [All] buildings [in this city]⟩; ⟨Must be on [Hill]⟩]. Re-based on hill country (Civ V has no seismic zones).
• Notes: Japanese/Incan-inspired.

CO08 · Modular Construction

• Tier: RARE · Era: Ancient
• Prerequisites: CO01 + SO05 (Specialization)
• Unlocks: ⟨[+25]% Production when constructing [All] buildings [in all cities]⟩ — standard parts, everywhere.
• Notes: Speculative: Roman standardization taken further.

CO09 · Suspension Bridge

• Tier: UNCOMMON · Era: Medieval
• Prerequisites: CO03 + (ME05 (Steel) or TX01 (Weaving — rope-making))
• Unlocks: ⟨[+1 Gold] from each Trade Route⟩; ⟨[+1 Production] [in all cities connected to capital]⟩ — the canyon crossed, the network pays.

CO10 · Iron-Frame Construction

• Tier: CORE · Era: Early Modern
• Prerequisites: ME08 + CO03
• Unlocks: Factory (the canonical Industrialization building: +4 Production; Production +10%; Engineer ×2). The ruleset derivation gives the canonical Factory ⟨Remove [Steam Works] [in this city]⟩: a Factory built where Steam Works stand converts them, twice as fast (the Steam Works' own clause), as a Steam Works converts an Engine House.
• Leads to: EL07 Power Grid, QM-E24 Self-Renewing Structures

CO11 · Reinforced Concrete

• Tier: STANDARD · Era: Modern
• Prerequisites: (CO04 or CH05) + ME12 — Roman Concrete, or the chemistry of Portland cement; and Bessemer steel
• Unlocks: ⟨[+10]% Production when constructing [All] buildings [in all cities]⟩ — steel and concrete build fast and stand hard; ⟨Improves movement speed on roads⟩ — the canonical Machinery unique, for cement roads (Portland Cement, merged here in v3.99: reinforced concrete was Portland cement and steel). Dams (WM06) become possible. Military Base; Bunkerⁿ [325/2; requires a Military Base in this city; cityStrength +8; cityHealth +50] — detached forts in concrete and steel (Ring Fortress, merged here in v3.125).
• Notes: Rifled shells made the bastion obsolete, and after 1885 high explosive did the same to masonry: the forts were rebuilt as a ring of detached works in concrete and steel — Liège, Verdun.
• Leads to: FA11 Vertical Farming, CO13 Geodesic Structures, SF13 Submarine, WM06 Dam Construction, SE01 Life Support Systems, SE02 Orbital Assembly

CO13 · Geodesic Structures

• Tier: UNCOMMON · Era: Atomic
• Prerequisites: CO11 + MA03 (Basic Algebra — trigonometry)
• Unlocks: ⟨[+15]% Production when constructing [Stadium] buildings [in all cities]⟩ — the dome over the arena. Any climate, enclosed.
• Leads to: CO15 Orbital Construction

CO14 · 3D Printed Construction

• Tier: RARE · Era: Atomic
• Prerequisites: MC11 (Assembly Line — prefabrication) + CP01 (Computer) + MS01 (Composites)
• Unlocks: ⟨[+33]% Production when constructing [All] buildings [in all cities]⟩ — printed, not built.

CO15 · Orbital Construction

• Tier: STANDARD · Era: Space
• Prerequisites: CO13 + SE02 (Orbital Assembly)
• Unlocks: Orbital Platformⁿ [560/3; +2 Production; ⟨[+10]% [Production] [in this city]⟩ — orbital industry; any city may have one]. Enables the Space Station (RK06) and the large orbital projects.
• Leads to: RK06 Space Station, RK12 Space Elevator

CO23 · Railway Network

• Tier: CORE · Era: Early Modern
• Prerequisites: MC08 (Steam Engine) + CO03 (Arch Construction — roads) + ME08 (Blast Furnace)
• Unlocks: Railroad (improvement — Civ V's built-in railroad connection bonus applies); Railway Stationⁿ [60/0; ⟨[+2 Gold, +1 Production] from each Trade Route⟩]; Neuschwanstein (world wonder). Distance stops mattering between connected cities.
• Notes: The defining infrastructure of the industrial age. Transforms the map — suddenly distance matters far less between rail-connected cities.

CO18 · Coral Architecture

• Tier: UNIQUE · Era: Ancient
• Prerequisites: CO01 + Coastal + Tropical biome
• Unlocks: Coral Wallsⁿ [replaces Walls; 75/0; cityStrength +6; cityHealth +50; ⟨Must be next to [Coast]⟩]; Reef Farmⁿ [improvement on Atoll and Coast; 3 turns; +1 Food]. Civ unique: ⟨[+1 Food, +1 Production] from [Atoll] tiles [in all cities]⟩ — the reef is quarry and larder.
• Notes: Pacific Islander/Maldivian coral construction.

CO19 · Crannog Lake Dwelling

• Tier: UNIQUE · Era: Ancient
• Prerequisites: CO01 + Lake/wetland terrain
• Unlocks: Crannogⁿ [replaces Walls; 75/0; cityStrength +7; ⟨[+1 Food] from [Lakes] tiles [in this city]⟩; ⟨Must be next to [Lakes]⟩]. Civ unique: ⟨[+1 Food] from [Marsh] tiles [in all cities]⟩ — the fen that keeps out armies feeds the village.
• Notes: Celtic/Swiss Lake Dweller tradition.

CO20 · Earthquake Mastery

• Tier: UNIQUE · Era: Classical
• Prerequisites: CO02 + Earthquake-prone region + MA01 (Geometry)
• Unlocks: Seismic Pagodaⁿ [replaces Monument; 40/1; +2 Culture; cityStrength +4; ⟨[-25]% maintenance cost for [All] buildings [in this city]⟩]. Civ unique: ⟨[-15]% maintenance cost for [All] buildings [in all cities]⟩. Re-based on Hill and Mountain country (Civ V has no seismic zones): flexible frames that stand where stone falls.
• Notes: Japanese/Incan seismic engineering.

CO21 · Ceremonial Road Network

• Tier: UNIQUE · Era: Classical
• Prerequisites: CO03 (Arch Construction — roads) + CU02 (Monumental Architecture) + Mountain or Jungle biome
• Unlocks: Pilgrimage Routeⁿ [improvement on Hill and Jungle; 5 turns; +1 Culture, +1 Faith]; Sacred Wayⁿ [national wonder; 100/0; +2 Culture, +2 Faith; ⟨[+1 Culture] from each Trade Route⟩]. Civ unique: ⟨[+1 Culture, +1 Faith] [in all cities connected to capital]⟩ — every city the sacred road reaches shares the rite.
• Notes: Incan royal roads, Roman Via Sacra, Maya sacbeob.

CO22 · Mound Builder Tradition

• Tier: UNIQUE · Era: Ancient
• Prerequisites: CO01 + SO03 (Tribal Law) + River + Grassland biome
• Unlocks: Earthen Moundⁿ [national wonder; 75/0; +3 Culture, +2 Faith]; Mound Platformⁿ [45/1; +1 Culture; cityStrength +4; cityHealth +25]. Civ unique: ⟨[+1 Culture] from [{River} {Grassland}] tiles [in all cities]⟩ — the river plain remembers its builders.
• Notes: Cahokia, Poverty Point, Hopewell earthworks.

CO24 · Concentric Fortification

• Tier: CORE · Era: Medieval
• Prerequisites: WA06 (Fortification Design) + CO03 (Arch)
• Unlocks: Castle (and the Mughal Fort); Alhambra (world wonder) — rings of walls and flanking towers: defence in depth.
• Notes: Krak des Chevaliers; Edward I's Welsh castles (12th–13th c.).

CO25 · Star Fort

• Tier: STANDARD · Era: Early Modern
• Prerequisites: WA06 + (WA22 Cannons or WA11 Trebuchet)
• Unlocks: Arsenal; Kremlin (world wonder) — low, angled bastions that turn a bombardment aside.
• Notes: The trace italienne (16th c.), the answer to cannon; where gunpowder never works, the trebuchet is the threat it answers.