Door Strength at a glance
| Lock (50) | 31s / 16s / 10s against 1 / 2 / 3 infected |
| Door (100) | 1m 3s / 31s / 21s |
| Reinforced (150) | 1m 34s / 47s / 31s |
| Board in the studs | +45 instead of +30 (screwed into the studs) |
| Caretaker repair | A door he repaired takes 15% less damage |
| Group size | Up to 3 infected at once, about 1.6 damage a second |
| Day 3 | 3 infected come for the door between 11:00 and 15:30 |
Time for the infected to break the door
| Door (integrity) | 1 infected / 2 / 3 |
|---|---|
| Lock (50) | 31s / 16s / 10s |
| Door (100) | 1m 3s / 31s / 21s |
| Reinforced (150) | 1m 34s / 47s / 31s |
How to read the table
The number in brackets is the door's integrity. The times are how long that door holds against one, two or three infected hitting it. game.guide says they attack in groups at the door, up to three at once, for about 1.6 damage a second, so the three-infected column is the one to plan for.
Day 3 is the first test. The guide says three infected come for the door between 11:00 and 15:30. Even a reinforced door holds only 31 seconds against three, so the door is meant to buy you time, not stop them.
What makes a door hold longer
- A board across the frame, screwed into the studs, adds +45 instead of +30.
- Furniture braced against a closed door holds "much better" than a lock alone. The game's Day 3 objective sends you to drag the couch to the marked position; see the barricade page.
- A door the Caretaker repaired takes 15% less damage.
What we haven't checked
These numbers come from a third-party guide. We haven't timed a door ourselves, and the guide doesn't give a number for braced furniture. If your run differs, tell us which door you had.
Tips
- Plan for three infected, not one: a reinforced door lasts 31s against three.
- Use a screwed board (+45) rather than a loose one (+30).
- Brace the door with furniture before Day 3, 11:00.
- Keep a retreat route; the survival guide says to listen at the door before opening it.
- Stay quiet so fewer infected come; see the noise page.
FAQ
How long does a door last in 30 Floors Up?
Against one infected: 31s for a lock, 1m 3s for a door, 1m 34s for a reinforced door (game.guide).
How long does a reinforced door last against three infected?
31 seconds, according to game.guide.
What does a board add?
+45 if it is screwed into the studs, +30 otherwise.
When is the first door attack?
Day 3, between 11:00 and 15:30, three infected (game.guide).
More 30 Floors Up pages
- 30 Floors Up Barricade: How to Brace the Door on Day 3
- 30 Floors Up Noise Levels: What Attracts the Infected
- 30 Floors Up Day by Day
- 30 Floors Up Daniel: How to Let Him In on Night 0
- 30 Floors Up beginner guide
- 30 Floors Up codes
- 30 Floors Up wiki: live stats
Sources
Checked Nov 13, 2026. Community wikis are edited by players, so numbers marked “per” one wiki may change after an update.