If you’ve spent any amount of time building bases in Subnautica, you’ve probably run into the same problem I did a few dozen playthroughs ago: you run out of horizontal space fast, and sprawling bases across the seabed attract unwanted attention from stalkers and sand sharks. That’s exactly why I started looking for how to make 2 stories in Subnautica, and after 200+ hours of testing builds across every biome, I’ve got a foolproof process that works for vanilla and modded playthroughs alike. You don’t need fancy mods or late-game resources to pull this off, either. Most players can put together a functional two-story base within their first few hours of a new save.
Pre-Build Prep: Resources and Location Checks
Before you start placing compartments, you want to make sure you have all the supplies you need on hand. I can’t tell you how many times I’ve gotten halfway through a build only to realize I forgot to grab extra lead for reinforcements, forcing me to swim 10 minutes back to a biome that has it. You don't need any mods to build a two-story base in the vanilla version of the game, so all these resources are easy to find in shallow biomes like the Safe Shallows or Grass Plateaus.
Here’s exactly what you’ll need for a basic two-story, two-compartment base:
You also want to pick your location carefully. I recommend sticking to depths above 100m for your first two-story build, since pressure penalties are much lower there. Avoid areas with steep drops or frequent leviathan spawns, because even a small hull breach can turn into a disaster if a reaper is swimming nearby. Always check your base hull integrity before adding a second floor, even if you’re building in very shallow water.
Step-by-Step Process for How to Make 2 Stories in Subnautica
Once you have your resources gathered and your spot picked out, the actual build process only takes 5 to 10 minutes if you don’t get distracted decorating. Start by placing your ground floor compartments first, and anchor them to a foundation piece if you’re building on uneven seabed. Unanchored compartments have lower base hull integrity, so that extra foundation is worth the two extra titanium it costs.
When your ground floor is placed and reinforced, equip your Habitat Builder and aim directly at the flat top surface of one of the ground floor compartments. You’ll see a placement prompt pop up for a new compartment, same as if you were placing it next to the existing one. Align the second floor compartment directly over the ground floor one, and click to place it. You don't need extra foundation pieces for the second floor if it's directly aligned with the ground floor compartments, which saves you resources and build time.
Next, you need to add a way to get between the two floors. Swim inside your ground floor compartment, aim at the ceiling directly below the second floor, and select the ladder option from the Habitat Builder menu. The ladder will automatically cut through the floor of the upper level, so you don’t have to make any extra modifications. Test the ladder to make sure it works, then add reinforcements to both floors until your hull integrity is at +5 or higher. I also recommend adding a hatch to the upper floor if you want quick access to the surface for scanning or resource collection.
Common Mistakes to Avoid With Your Two-Story Base
Even with a simple build process, it’s easy to make small mistakes that turn your new base into a leaking mess. One of the most common errors new players make when figuring out how to make 2 stories in Subnautica is ignoring hull integrity alerts. Each extra floor you add adds a -1 penalty to your base hull integrity, and that penalty gets worse the deeper you build. Hull integrity drops faster for multi-story bases built below 200m, so add at least 2 reinforcements per extra floor if you’re building in deeper biomes like the Grand Reef or Lost River.
Another common mistake is forgetting to upgrade your power source. A single solar panel can power a small one-story base easily, but two floors mean more lights, more storage, more fabricators, and often more grow beds or water purifiers. If you’re building below 50m, swap out solar panels for bioreactors early, because sunlight penetration drops fast at those depths and your power will cut out every night.
I also see a lot of players block the ladder entry on the upper floor with storage lockers or furniture. I did this on my first two-story base, and I had to deconstruct half my storage just to get up to the second floor to fix a leak. Leave a 1x1 space clear around the ladder top on the upper floor, and you won’t run into this issue. If you want an overhang on your second floor, make sure you add extra support pieces to offset the integrity penalty, otherwise it’ll spring a leak the second you place it.
Creative Upgrades for Your Two-Story Subnautica Base
Once your basic two-story base is functional, you can customize it to fit your playstyle without much extra work. One of my favorite upgrades is turning the entire upper floor into a glass viewing lounge. Swap the standard titanium compartments for glass ones, add a chair and a jukebox, and you can watch reefbacks and other passive creatures swim by without ever leaving your base. It’s also a great spot to park your seamoth if you attach a moonpool to the upper level.
I also recommend splitting your floors by purpose to keep your base organized. Use the ground floor for all your utility items: fabricators, storage lockers, medical kits, and water purifiers. Keep the upper floor for farming, grow beds, and your bioreactor, so you don’t have rotting kelp or fish near your crafting area. This setup also makes it easier to find what you need fast when you’re in a hurry to heal up after a run-in with a stalker.
If you’re playing on a save where you explore a lot, you can add exterior grow beds to the edge of the upper floor to grow creepvine, coral tubes, and other resources you use regularly. That way you don’t have to swim 20 minutes to find creepvine seeds when you need to make silicone rubber. You can add a moonpool attached directly to either floor as long as you have enough space and hull integrity, which makes docking your seamoth or prawn suit way faster than using a standard exterior hatch.
Building up instead of out is one of the most underrated tricks for surviving Subnautica’s harsh open ocean. Once you know how to make 2 stories in Subnautica, you can fit twice as much utility into a small footprint, which reduces your chance of attracting hostile creatures and cuts down on the time you spend running between storage and crafting stations. Play around with different layouts and upgrades to find what works for your playstyle, and don’t be afraid to tear down and rebuild if your first design doesn’t fit your needs. My current main base is 4 stories tall, and it all started with the same basic two-story build I walked through here.
