To repair a damaged foundation or structure in Raft, you use the Building Hammer. With the hammer equipped, look at a damaged piece of your raft and switch to repair mode, then click to fix it. Each repair from 50% health costs one Plank, making it a cheap but essential habit to maintain your floating home.
How Repair Mode Works
The Building Hammer is the only tool that can repair structures. You likely already have one since it’s the same tool you use to place foundations and walls. With it equipped, right-click to cycle through its modes until you reach the repair function. Then simply aim at a damaged block and left-click to restore it.
A foundation at 50% health costs just one Plank to bring back to full. That’s half the cost of building a new foundation from scratch, so repairing is always more resource-efficient than letting a block get destroyed and replacing it. If a block does break completely, anything built on top of it (walls, furniture, stations) disappears with it, costing you far more than a single Plank would have.
Why Your Raft Takes Damage
The shark circling your raft attacks foundations that sit at water level on a roughly five-minute timer. It picks an exposed outer edge, latches on, and chews through the block over several bites. If you ignore it, the foundation breaks and is gone. The shark only targets pieces touching the water, so anything built above the waterline on a second floor is safe from bites.
This means your raft’s footprint on the water directly determines how many vulnerable tiles you have. A compact design or a catamaran-style build (two narrow hulls connected by upper platforms) reduces the number of exposed foundations and makes defense much simpler.
Foundation Armor: The Permanent Fix
Repairing every five minutes gets old fast. The real solution is Foundation Armor, a craftable upgrade that makes any water-level structure completely immune to shark attacks. Once armored, a foundation or Collection Net can never be bitten again.
Each piece of Foundation Armor requires one Metal Ingot and two Nails. Metal Ingots come from smelting Metal Ore, which you find on reef islands underwater or occasionally in barrels. Nails are crafted from Metal Ingots as well, so you’ll need a steady supply of ore before you can armor up your whole raft.
You don’t need to armor every single tile. Only foundations on the outer water-level perimeter are at risk, so focus your Metal Ingots there first. Interior tiles that are surrounded on all sides by other foundations won’t get targeted. Prioritize armoring Collection Nets too, since losing a net means losing both the structure and whatever resources it had gathered.
Strategies While You Gather Metal
Early in the game, you won’t have enough metal to armor anything. Here are practical ways to manage shark damage until then:
- Repair promptly. One Plank every five minutes is a tiny cost. Keep a small stack of Planks in your inventory and fix bites as they happen.
- Use sacrificial foundations. Place cheap triangle foundations on your raft’s outer corners as bait. The shark tends to target these. If it starts chewing one, you can break the triangle yourself with your axe before the shark finishes, recovering all the building materials. The shark wastes its attack, and you lose nothing.
- Distract with spare tiles. When you need to dive underwater for resources, place an extra foundation or two in the water beforehand. The shark will focus on those instead of you.
- Kill the shark. A Metal Spear takes it down after several hits. The shark respawns after about ten minutes, or as little as three minutes if you fully loot its body. Killing it buys you a window of peace for diving and building.
- Minimize your water footprint. Build upward instead of outward. Every foundation you add at water level is another potential target, but second-story platforms give you space without adding vulnerability.
Repair vs. Rebuild: What Costs Less
Repairing is always cheaper than replacing. A new wooden foundation costs two Planks, while repairing one at half health costs just one. But the real savings come from protecting what’s built on top. A destroyed foundation takes down any walls, floors, or stations above it. Losing a Smelter or Research Table because the foundation underneath got eaten is a painful setback that a single Plank of repair would have prevented.
Once you have Foundation Armor on all your outer tiles, repair costs drop to zero and you can stop worrying about the shark entirely. Getting to that point is one of the most satisfying milestones in the game, so treat metal gathering as a top priority whenever you reach a new island.