Hull integrity is the core mechanic governing whether your base stands or floods. Every base piece has an integrity value: positive pieces like Foundations and Reinforcements add integrity, while negative pieces like Windows and large rooms subtract it. Your base's total integrity must stay above zero, or structures begin to leak and flood. The deeper you build, the higher the integrity penalty per piece, because water pressure increases with depth. A window that costs 1 integrity at 20 meters might cost 3 at 200 meters.
The integrity cost of each piece is displayed in the Habitat Builder menu before placement. Foundations add 5 integrity each and are the most efficient way to stabilize a base. Reinforcements add 1.5 integrity and can be attached to any vertical surface, making them ideal for retrofitting existing bases. Bulkheads add 1 integrity and serve the dual purpose of compartmentalization. Windows subtract integrity, with the Large Window being the costliest, so use them sparingly in deep bases. The general rule is to over-build foundations rather than risk a negative integrity total.
To check your base's status, look at the integrity meter in the Habitat Builder interface while inside the base. If it approaches zero, add Reinforcements or Foundations immediately. A base that hits negative integrity will develop leaks that flood connected rooms, damaging equipment and destroying stored items that are not waterproof. Prevention is far cheaper than repair, so always build with a positive integrity buffer of at least 5 to account for future expansions and accidental removals.
Understanding Hull Integrity
Hull integrity is the core mechanic governing whether your base stands or floods. Every base piece has an integrity value: positive pieces like Foundations and Reinforcements add integrity, while negative pieces like Windows and large rooms subtract it. Your base's total integrity must stay above zero, or structures begin to leak and flood. The deeper you build, the higher the integrity penalty per piece, because water pressure increases with depth. A window that costs 1 integrity at 20 meters might cost 3 at 200 meters.
The integrity cost of each piece is displayed in the Habitat Builder menu before placement. Foundations add 5 integrity each and are the most efficient way to stabilize a base. Reinforcements add 1.5 integrity and can be attached to any vertical surface, making them ideal for retrofitting existing bases. Bulkheads add 1 integrity and serve the dual purpose of compartmentalization. Windows subtract integrity, with the Large Window being the costliest, so use them sparingly in deep bases. The general rule is to over-build foundations rather than risk a negative integrity total.
To check your base's status, look at the integrity meter in the Habitat Builder interface while inside the base. If it approaches zero, add Reinforcements or Foundations immediately. A base that hits negative integrity will develop leaks that flood connected rooms, damaging equipment and destroying stored items that are not waterproof. Prevention is far cheaper than repair, so always build with a positive integrity buffer of at least 5 to account for future expansions and accidental removals.
Reinforcement Strategies by Depth
Reinforcement strategy should scale with depth. For shallow bases under 50 meters, a single Foundation per three rooms is usually sufficient, and you can afford to use windows liberally for aesthetics. For mid-depth bases from 100 to 200 meters, plan for one Foundation per two rooms and add Reinforcements to any wall without a window. Deep bases from 300 meters and up require aggressive reinforcement: Foundations under every room, Reinforcements on every available wall, and bulkheads between every compartment.
A powerful technique for deep bases is the Foundation Grid, where you lay a connected grid of Foundations before building rooms on top. This maximizes integrity per Titanium spent and creates a stable platform that resists flooding even if one room is breached. The grid approach costs more materials upfront but dramatically reduces the risk of catastrophic collapse. Pair it with Bulkheads between rooms so that a breach in one compartment does not cascade through the entire base.
The Reinforced Window, added in the 1.1 update, is a game-changer for deep bases. It offers the aesthetic of a window with a much lower integrity penalty than standard windows, letting you build observation decks at depth without compromising stability. Use Reinforced Windows for any deep-base viewports and reserve standard windows for shallow structures. Additionally, the Reinforced Dive Suit and upgraded vehicle hulls do not affect base integrity, so do not confuse personal crush depth with base crush depth; they are independent systems.
| Piece | Integrity | Notes |
|---|---|---|
| Foundation | +5 | Best stability per cost |
| Reinforcement | +1.5 | Attach to any wall |
| Bulkhead | +1 | Compartmentalizes flooding |
| Large Window | -2 to -3 | Avoid in deep bases |
| Reinforced Window | -0.5 | Safe at depth |
Bulkheads and Flood Containment
Bulkheads are the most important flood-prevention tool in the game. A bulkhead is a reinforced door that seals a compartment, preventing water from spreading between rooms if one floods. Without bulkheads, a single breach can flood an entire connected base, destroying equipment and storage. With bulkheads, a breach is contained to one room, which you can drain and repair without losing the rest of your base. Every deep base should have bulkheads separating critical compartments like the power room, storage, and vehicle bay.
The ideal bulkhead layout creates zones that can be isolated. Place a bulkhead at the entrance to each major room and at every corridor junction. This way, if the vehicle bay floods, the storage and fabrication rooms remain dry. When a flood occurs, the bulkhead doors automatically seal, and a red warning indicator appears on your HUD. To drain a flooded room, repair the breach with the Repair Tool, then use the bulkhead to pump the water out. The pumping process takes a few seconds, during which the room remains inaccessible.
A common mistake is building long, open corridors without bulkheads. These act as flood highways, letting water travel from a breach to distant rooms almost instantly. Break up long corridors with bulkheads every two or three segments. Another mistake is placing power systems in a room without a bulkhead, because a flooded power room disables the entire base, including water pumps needed to drain it. Always isolate power and life support behind bulkheads so that a flood cannot create a recovery-impossible situation.
Pro Tips and Building Checklist
Beyond integrity and bulkheads, several pro tips keep your base secure. First, always build a Foundation before the first room; starting a base on bare terrain invites instability. Second, place power systems and water filtration above the base's lowest point so that minor flooding does not disable them. Third, keep a Repair Tool and spare Titanium in an accessible waterproof container, because you will need fast access during a flood emergency. Fourth, build a backup air supply using a pipe network to the surface for shallow bases, giving you a fallback if life support fails.
For deep bases, consider the compartmentalized pod design: several small, self-contained rooms connected by bulkhead-sealed corridors, each with its own minimal power and air. If one pod floods, the others remain operational, and you never lose your entire base to a single event. This design is material-intensive but offers the highest resilience for deep operations. Pair it with a vehicle bay that is separately bulkheaded, because vehicle bays are the most common breach point due to their large openings.
Use this building checklist before considering any base complete: integrity meter above 5 with buffer, bulkheads between every compartment, power isolated behind a bulkhead, repair tools and spare materials accessible, Scanner Room online to detect nearby threats, and an escape vehicle docked. A base that passes this checklist will survive predator attacks, accidental breaches, and expansion mistakes. Base building in Subnautica 2 rewards careful planning, and a flood-proof base is the foundation of a stress-free deep-biome operation.
- Build a Foundation before the first room
- Maintain integrity buffer of at least 5
- Bulkhead every compartment, especially power
- Use Reinforced Windows at depth
- Keep repair tools and Titanium accessible
- Dock an escape vehicle at deep bases