Every building piece starts as twig and can be upgraded through four tiers. Each tier has more health, costs more to raid, and requires more upkeep. Costs vary by piece type. A wall costs more to upgrade than a floor. Knowing the numbers tells you where to spend resources first.

The Five Tiers

Twig Wall
Twig 10 HP
The default when any piece is placed. No meaningful health. Anyone can destroy twig with a few hits from any tool. Decays in one hour regardless of TC stock. Never leave twig inside a finished base.
Place: 50 wood
Raid: 1 hit
Wood Wall
Wood 250 HP
Cheap and fast. Enough to slow early-wipe players without explosives. Burns with fire and can be hatcheted on the soft side. Upgrade to stone as soon as you have the resources. Upgrade cost varies by piece: walls cost more than floors.
Upgrade: 100–200 wood
Satchels: 3
C4: 1
Rockets: 1–2
Stone Wall
Stone 500 HP
The baseline for a defended base. Immune to fire. Requires explosives through the hard side. The soft side can still be pickaxed, so placement matters. Most outer walls stay at stone for the majority of the wipe.
Upgrade: 75–300 stone
Satchels: 10
C4: 2
Rockets: 4
Metal Wall
Sheet Metal 1,000 HP
Double the health of stone. No soft side pickaxe weakness. Best used on TC rooms, loot rooms, and inner walls where you need to force more explosive spend. Higher upkeep than stone.
Upgrade: 50–150 metal frags
Satchels: 23
C4: 4
Rockets: 8
Armoured Wall
Armoured 2,000 HP
The toughest tier. Very expensive to build and upkeep. Rarely worth it on outer walls. Raiders will go around or the upkeep will drain you. Reserve for the TC room and innermost loot room where forcing maximum raid cost matters.
Upgrade: 7–25 HQM
Satchels: 46
C4: 8
Rockets: 15
You can skip tiers You can upgrade directly from twig to stone, or wood to metal. You do not have to go through every tier in order. If you have stone, skip wood entirely.

Raid Cost Reference

Hard side costs. Soft side is significantly cheaper on wood and stone. Sheet metal and armoured have no soft side pickaxe weakness.

TierHPSatchelsC4RocketsSoft side
Wood250311–2Hatchet / fire
Stone5001024Pickaxe
Sheet Metal1,0002348No weakness
Armoured2,00046815No weakness
Doors are cheaper to raid than walls A sheet metal door costs roughly 4 satchels. A stone wall costs 10. Raiders always try the door first. See the Doors and Locks guide for door raid costs.

What to Upgrade First

Upgrade what a raider hits first. Outer walls before inner walls. The wall facing the most open approach before the wall facing a cliff. Full stone base first, then TC room walls and door to sheet metal, then the airlock. Armoured is for the TC room wall and door once HQM is coming in.

Upgrading floors is often skipped. Ground floor loot room floors at armoured cost far less than walls and stop raiders picking up through the base from below.