There is no tech tree. There is only population.
SteamWorld Build hides one of its most important systems. There is no research, no quest chain and no story gate on what you can build — every single building is locked behind a population count, and if you cannot build something, it is because you do not have enough bots.
The part that trips everyone up is that the currency changes three times.
The real ladder is:
| To unlock | You need |
|---|---|
| Engineers | 200 Workers (Milestone 4) |
| Aristobots | 240 Engineers (Milestone 9) |
| Scientists | 240 Aristobots (Milestone 14) |
The reset trap
You will grind to 200 Workers, unlock Engineers, and then watch your milestone tracker drop to 1 Engineer for Milestone 5.
That is not a bug and it is not progress being lost. Each tier counts its own population. The moment a new tier appears, the counter starts over at 1 of that tier — and then climbs all the way back up to 240 of them before the next tier appears.
So the shape of the game is three identical 240-bot climbs, and the only thing that gets you up each one is satisfying needs and laying better roads.
All 19 milestones
| # | Reached when | Overworld unlocks | Mine unlocks |
|---|---|---|---|
| 1 | 24 Workers — 6 houses with General Store access | Warehouse, Forester, Lumbermill, Service Shop | — |
| 2 | 70 Workers — 12 houses with General Store and Service Shop access | Cactus Farm | — |
| 3 | 120 Workers — 15 houses with General Store, Service Shop and Cactus Water, or 20 houses without Cactus Water | Charcoal Kiln, Train Station | — |
| 4 | 200 Workers | Engineers | — |
| 5 | 1 Engineer | Sand Sifting Factory, Glassblower, Moonshiner, Saloon | — |
| 6 | 70 Engineers | Repair of Abandoned Mineshaft (18 Engineers), Toolmaker, Surveyor Office, Paved Road | Miners Quarters, Prospector Quarters |
| 7 | 120 Engineers | Pickaxe Maker, Sheet Metal Factory, Spare Parts Maker, Scrap Extractor | Mechanic Quarters |
| 8 | 200 Engineers | Wash Service, Burger Meister | Water Purifier, Bridges, Surveillance Factory with Radar, Dirty Water Extractor |
| 9 | 240 Engineers | Aristobots | — |
| 10 | 1 Aristobot | Waxing Shop, Polymerisation Plant | — |
| 11 | 80 Aristobots | Sheriff’s Office, Armory, Diesel Plant, Hatmaker, Glass Wool Spinner, Oil Refinery | Guard Quarters, Grenade Turret, Oil Extractor, Thumper |
| 12 | 120 Aristobots | Fine Dining Restaurant, Steam Furnace, Carburizing Plant | — |
| 13 | 180 Aristobots | Casino, Gunsmith, Black Powder Maker, Sulfur Distillery | Flame Turret, Gas Extractor |
| 14 | 240 Aristobots | Scientists | — |
| 15 | 1 Scientist | Maglev Road, Retrofit Shop, University | — |
| 16 | 50 Scientists | Lab Equipment Manufacturer, Sparkling Diesel Manufacturer | Lightning Turret |
| 17 | 100 Scientists | Art Studio, Oil Paint Factory, Large Stuff Collider | Vectron Scrap Extractor |
| 18 | 150 Scientists | Observatory | — |
| 19 | 240 Scientists | Jetshroom Farm, Rocket Fuel Processing Plant | — |
“Why can’t I build X?” — the answers
| You want | You need |
|---|---|
| Toolmaker | Milestone 6 — 70 Engineers |
| Paved Road | Milestone 6 — 70 Engineers |
| Pickaxe Maker (to break Sandstone) | Milestone 7 — 120 Engineers |
| Bridges | Milestone 8 — 200 Engineers |
| Thumper (to stop Worms) | Milestone 11 — 80 Aristobots |
| Carburizing Plant (to break Granite) | Milestone 12 — 120 Aristobots |
| Maglev Road | Milestone 15 — 1 Scientist |
| Lightning Turret | Milestone 16 — 50 Scientists |
The Granite one is the nastiest. Hitting a Granite wall feels like a mining problem, and the answer is 120 Aristobots — three tiers up the ladder.
The two quirks worth knowing
The Mineshaft repair has its own separate number. Milestone 6 arrives at 70 Engineers, but repairing the Abandoned Mineshaft inside it needs only 18 Engineers. You will unlock the option long before you can staff it, and the milestone itself is not the thing to watch.
Decorations do nothing. Milestones do unlock more of them, but they do not help production and they do not help bot happiness. Build them because you like how the town looks, not because they will make anything work.
The Engineer tier is where the game opens up
Three buildings that arrive in the Engineer tier are worth building the moment they unlock, and their numbers are worth knowing:
| Building | Build cost | Upkeep | What it does |
|---|---|---|---|
| Toolmaker | 3,000 dollars, 10 boards | 9 dollars, 15 Engineers | 1 Scrap → 1 Tool, every 15 seconds |
| Pickaxe Maker | 6,000 dollars, 10 boards, 10 Tools | 18 dollars, 30 Engineers | 1 Wood + 1 Scrap → 1 Pickaxe, every 30 seconds |
| Sheet Metal Factory | 11,000 dollars, 15 boards, 8 Tools | 8 dollars, 15 Engineers | 1 Ironium → 1 Sheet Metal, every 15 seconds |
Two practical notes:
- Run two Toolmakers early. From Milestone 6 onward, Tools are needed for roads, buildings and every underground facility, and demand never drops. At least until the Aristobot phase, one is not enough.
- The Pickaxe Maker wants 30 Engineers, which is far above the average. If you have an item that reduces the workforce requirement, put it there.
Related guides
- steamworld build guide: best city layout
- steamworld build money
- steamworld build granite
- steamworld build worms
- steamworld build storage
- steamworld build save location
- tips and tricks
- beginner guide
- common mistakes
- upgrades guide
- steamworld dig guide
- steamworld dig 2 collectibles
- steamworld heist guide
- series order guide