Wave Counts: When the Boss Arrives
What this page helps you decide: when to spend and when to save, based on how long the room you are in actually runs
Room length is the least quoted number in the game and one of the most useful, because it decides whether early spending compounds or whether you should hold. Floors 3 and 4 turn out to use exactly the same boss schedule - waves 15, 17, 18, 19 and 21 - so once you know which room you are in, you know how long you have.
Floors 3 and 4 share one schedule
On Floor 3 the finales arrive on waves 15, 17, 18, 19 and 21 for rooms one through five. On Floor 4 they arrive on waves 15, 17, 18, 19 and 21 for rooms one through five. Ten rooms across two floors with identical timing is not a coincidence - room length is set by position within the floor rather than by which floor it is. That means you can carry timing knowledge from Floor 3 straight into Floor 4 even though every enemy, layout and health value has changed. It also means the fifth room of any floor is the long one, and should be played differently from the first.
Longer rooms reward earlier spending
Floor 1 runs a flat 15 waves per room. By the fifth room of Floor 3 or Floor 4 you have 21, which is 40% more income before the fight. An upgrade bought on wave 6 of a 21-wave room is working for fifteen more waves; the same upgrade in a 15-wave room works for nine. That difference is why holding money for the boss is a defensible habit on Floor 1 and a losing one in the last room of a later floor. If you carry the Floor 1 spending pattern forward without noticing the rooms got longer, you arrive at the boss with money you should have converted into damage ten waves ago.
Horror Mode changes the lengths again
Horror Mode Floor 2 does not follow the same schedule as the normal floors: its rooms run 15, 18, 19, 18 and 21 waves. Room four is shorter than room three there, which breaks the otherwise monotonic pattern. The safest reading is that Horror Mode rooms were tuned individually rather than inheriting the normal-mode schedule, so check the length for the specific Horror room rather than assuming. What does carry over is the direction: Horror Mode rooms are longer than their normal counterparts, so the spend-early conclusion applies there even more strongly.
The boss is not always the last wave
In several rooms the heaviest wave is not the last one. The Mastermind Core sends three Abominations on wave 20, one wave before the 495,000 boss on wave 21 - back to back with no recovery. Horror Mode Rabbit Hole peaks on wave 16 with the boss on 18. When you plan around a wave number, plan around the heaviest wave rather than the last one, because arriving at the finale with a depleted board is functionally the same as failing at the finale.
Step-by-Step
- Identify which room number you are in - the schedule follows position, not floor.
- Rooms one to five run bosses on waves 15, 17, 18, 19 and 21 on Floors 3 and 4.
- In 21-wave rooms, convert money into damage early rather than holding for the boss.
- Check Horror Mode room lengths individually - they do not follow the normal schedule.
- Plan around the heaviest wave, which is sometimes one before the finale.
Data Tables
| Room position | Floor 3 | Floor 4 | Horror Floor 2 |
|---|---|---|---|
| Room 1 | Wave 15 | Wave 15 | 15 waves |
| Room 2 | Wave 17 | Wave 17 | 18 waves |
| Room 3 | Wave 18 | Wave 18 | 19 waves |
| Room 4 | Wave 19 | Wave 19 | 18 waves |
| Room 5 | Wave 21 | Wave 21 | 21 waves |
Figures are player-reported in community video WSIfdqA6Ja4 by Rubenakayoshii, not developer-published. Ratios, shares and expected values are our own arithmetic on those figures. Checked 2026-08-27.
Tips & Notes
- Room length is set by position within the floor, not by the floor - the fifth room is always the long one.
FAQ
How many waves are in a room in The House TD 2?
Floor 1 runs 15 waves per room. On Floors 3 and 4 the boss arrives on waves 15, 17, 18, 19 and 21 for rooms one through five.
Do Floor 3 and Floor 4 really use the same wave numbers?
Yes. All ten documented rooms across the two floors place their finale on the same wave as the equivalent room on the other floor.
Should I save money for the boss?
Not in long rooms. In a 21-wave room an upgrade bought on wave 6 works for fifteen more waves, so early spending compounds well past what holding can match.
Sources
- Community Floor 3 Mad Labs Guide by Rubenakayoshii
- Community Floor 4 Guide by Rubenakayoshii