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 building's output 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
Level n to n+1 costs the build price × 1.8ⁿ and takes the build time × 2ⁿ (at least 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 · 8 min | 175 / 85 · 16 min | 315 / 155 · 32 min |
| Rot Garden | 35 / 45 · 4 min | 65 / 80 · 8 min | 115 / 145 · 16 min | 210 / 260 · 32 min |
| Binding Pit | 70 / 55 · 12 min | 130 / 95 · 24 min | 235 / 175 · 48 min | 420 / 315 · 96 min |
| Serum Lab | 80 / 45 · 40 min | 145 / 80 · 80 min | 260 / 145 · 160 min | 470 / 260 · 320 min |
| Watchtower | 55 / 65 · 40 min | 95 / 115 · 80 min | 175 / 205 · 160 min | 315 / 365 · 320 min |
| Warehouse | 90 / 70 · 10 min | 160 / 130 · 20 min | 290 / 235 · 40 min | 525 / 420 · 80 min |
| Barricade | 20 / 20 · 2 min | 30 / 30 · 4 min | 60 / 60 · 8 min | 105 / 105 · 16 min |
| Road gate | 70 / 110 · 10 min | 130 / 195 · 20 min | 235 / 350 · 40 min | 420 / 630 · 80 min |
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 what the building does by 1.6: production, safe stock, barricade hp and tower fire, and towers 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.