Building upgrades and specializations: which path to pick
Updated September 25, 2026. Figures come from the live game.
The short answer
Each upgrade multiplies a producer's output by 1.35 (towers, warehouses and barricades by 1.6). At levels 3 and 5 you pick one of two permanent paths. For most players: Roaring Furnace or Quiet Presses depending on how loud you play, Distillery on the Lab, Rapid Binding on the Binding Pit, Longwatch on the tower and Strongroom on the warehouse.
What upgrades cost
The first two upgrades cost the build price × 1.8 each; from level 3 → 4 on, each level costs 4.5 times the one before. Upgrades to level 3 and up also cost biomass, and the Serum Lab, Watchtower and Warehouse take some serum too. Time doubles each level (producers start from a 10-minute base past level 2, and nothing takes under 2 minutes). Your mini-game grade then cuts the time. Upgrades share the construction slot, and the building keeps working at its old level until the timer ends.
| Building | 1 → 2 | 2 → 3 | 3 → 4 | 4 → 5 |
|---|---|---|---|---|
| Scrapworks | 55 / 25 · 4 min | 95 / 50 + 50 biomass · 40 min | 435 / 220 + 220 biomass · 1 h 20 min | 1,970 / 985 + 985 biomass · 2 h 40 min |
| Rot Garden | 35 / 45 · 4 min | 65 / 80 + 50 biomass · 40 min | 290 / 365 + 230 biomass · 1 h 20 min | 1,310 / 1,640 + 1,050 biomass · 2 h 40 min |
| Binding Pit | 70 / 55 · 12 min | 130 / 95 + 105 biomass · 24 min | 585 / 435 + 470 biomass · 48 min | 2,625 / 1,970 + 2,100 biomass · 1 h 36 min |
| Serum Lab | 80 / 45 · 40 min | 145 / 80 + 75 biomass + 60 serum · 1 h 20 min | 655 / 365 + 330 biomass + 260 serum · 2 h 40 min | 2,950 / 1,640 + 1,475 biomass + 1,180 serum · 5 h 20 min |
| Watchtower | 55 / 65 · 40 min | 95 / 115 + 50 biomass + 20 serum · 1 h 20 min | 435 / 510 + 220 biomass + 85 serum · 2 h 40 min | 1,970 / 2,295 + 985 biomass + 395 serum · 5 h 20 min |
| Warehouse | 90 / 70 · 10 min | 160 / 130 + 80 biomass + 15 serum · 20 min | 730 / 585 + 365 biomass + 75 serum · 40 min | 3,280 / 2,625 + 1,640 biomass + 330 serum · 1 h 20 min |
| Barricade | 20 / 20 · 2 min | 30 / 30 + 15 biomass · 4 min | 145 / 145 + 75 biomass · 8 min | 655 / 655 + 330 biomass · 16 min |
| Road gate | 70 / 80 · 10 min | 130 / 145 + 105 biomass · 20 min | 585 / 655 + 470 biomass · 40 min | 2,625 / 2,950 + 2,100 biomass · 1 h 20 min |
On a fully expanded island road gates keep climbing past level 5, up to level 10: from 3,020 scrap, 1,055 timber, 905 biomass and 665 serum for 5 → 6, rising 15 % a level. They are the late game's long project.
Buildings can go past level 5 too, up to level 10, once the island is fully expanded and you have reached a league at least once: Iron unlocks level 6, Steel 7, Chrome 8 and Warlord 9 and 10. A bad week later never takes an unlocked level away. Each level past 5 costs about twice the last and takes 1.5 times as long, up to 24 h: a Scrapworks 5 → 6 costs 3,935 scrap, 1,970 timber and 1,970 biomass and takes 4 h.
The upgrade panel shows now-versus-next stats, the price and the time for each grade.
Every specialization path
The choice is permanent and the building shows it. Levels 3 and 5 are also gated by the island: level 3 needs your second expansion.
| Building | Level 3 | Level 5 |
|---|---|---|
| Scrapworks | Quiet Presses (no noise, −10 %) or Roaring Furnace (+25 %, +1 noise a minute) | Salvage Yard (raids +15 % loot) or Foundry (+20 %) |
| Rot Garden | Fungal Beds (+30 % biomass) or Timber Grove (+50 % timber) | Seed Vault (+150 storage, +10 serum) or Blight Farm (+40 % biomass, +noise) |
| Binding Pit | Rapid Binding (−40 % bind time) or Mutagen Vats (mutations −30 %) | Brood Pens (+2 horde cap per Pit level) or War Pit (new squads start at level 2) |
| Serum Lab | Distillery (+25 % serum) or Catalyst Stores (+50 % serum storage) | Deep Research (−25 % research time) or Serum Reserve (−30 % serum for research and binding) |
| Watchtower | Longwatch (+3 range, +1 vision) or Rapid Fire (+40 % shots) | Flare Tower (+2 vision past the cap) or Ballista (×2 damage to brutes) |
| Warehouse | Strongroom (×2 safe stock) or Depot (×1.5 storage) | Smuggler's Den (+3 gold a bounty) or Vault (×1.5 safe, ×1.3 storage) |
| Barricade, gate | Spiked (15 damage a second to hitters) or Reinforced (+30 % hp) | Tar Pit (attackers near it slow to 60 %) or Iron Gate (+40 % hp, no Wallbreaker bonus) |
How to choose
- Scrapworks: if you play loud, Roaring Furnace stacks with the loud bonus. If wild hordes keep finding you, Quiet Presses removes that scrapworks' noise entirely.
- Serum Lab: Distillery if serum is your bottleneck, which it is for most players. Catalyst Stores if your serum tank fills between visits.
- Binding Pit: Rapid Binding if you bind every session; Mutagen Vats only once you're mutating squads every week. At level 5, Brood Pens for a bigger horde or War Pit for tougher new squads.
- Watchtower: Longwatch shows raids earlier and hits from further; Rapid Fire wins if you're raided often at close range.
- Warehouse: Strongroom doubles what raiders can never take. Pick Depot only if you keep hitting the cap between visits.
- Barricade and gate: Reinforced is the safe pick. Iron Gate at level 5 shuts down Wallbreaker brutes.
Questions players ask
Can I change a specialization later?
No. The level-3 and level-5 choices are permanent.
What does each building level do?
Every level multiplies a producer's output by 1.35, and safe stock, barricade hp and tower fire by 1.6; towers also reach one cell further per level. Warehouse storage grows faster: a level-2 Warehouse holds 2.59 times a level-1, and a level-5 holds 12.36 times.
Does the Serum Lab's level matter?
Yes. Research level n needs a level-n lab. Binding is the Binding Pit's job: the Pit adds one zombie to each batch at level 3 and another at level 5, and binds 8 % faster per level above 1.
My Serum Lab has Rapid Binding or Mutagen Vats. Did I lose it?
No. Labs that took those paths before the Binding Pit arrived keep them, and the bonus applies to binding and mutations once you build a Pit. New Labs are offered Catalyst Stores and Serum Reserve instead.