Background walls, also just known as walls, are tiles that create backgrounds on top of biome backgrounds. Walls are hidden behind everything else, such as blocks. Natural walls are generated at world creation, being abundant in certain biomes like the Underground Jungle, and are of the main components a Terraria world consists of alongside blocks and liquids. Walls can be removed with a hammer or explosives.
Many wall types exist as items that the player can place in their inventory and then re-place in any area which does not already have walls. Certain mechanics of walls is dependent on which of the following categories they fall under:
- Safe walls prevent enemies from spawning (but do not do anything to prevent their passage), and a mostly unbroken background of safe walls is necessary for a structure to qualify as a NPC house, or to use a Bed to change a player's spawn point. Safe walls are usually obtained from crafting, or purchased from NPCs, but can also be found naturally in certain structures, such as Shrines and Pyramids.
- Unsafe walls are a type of wall that appears during world generation, and can generally not be utilized by the player; when broken, they will either drop their safe equivalent or nothing at all. Unsafe walls will not stop enemies from spawning, and cannot be utilized for houses. They also have a quirk in that they must be removed by starting from their edge (i.e., adjacent space with no wall), which for explosives means that an edge must exist somewhere within the radius of the explosion.
Differing safe walls from unsafe walls can be tricky because many walls, such as Obsidian Brick Walls or Dungeon Brick Walls, exist in both safe and unsafe forms. With these walls (both of which are harvestable), the player must break the unsafe walls and replace them in order for them to count as safe walls. Similarly, many (or all, on ) naturally-generated walls have safe counterparts which are obtainable through crafting or purchase from NPCs.
These walls are made by the player using various crafting materials. All crafted walls qualify for housing.
These walls are purchased from various NPCs. All purchased walls except Sail qualify for housing.
These walls can be harvested in various places when exploring the world. Most of them can also be obtained through crafting. All harvested walls qualify for housing.
These walls are normally created by biome spread. They can also be made using Solution sprayed with the Clentaminator, and on the Desktop version and Mobile version they can also be crafted or purchased (with the exception of the natural Mushroom Wall). On the Console version, Old-gen console version, and version the Clentaminator is the only way the player can make these walls. These walls qualify for housing when they are crafted or purchased, but do not if they are created by biome spread or the Clentaminator.
- Dirt Walls generally completely cover the background at Underground depths above zero (see Layer, Depth Meter). Placing new walls in this area would require first tearing down the existing walls starting from the top (the Surface) or the bottom (zero depth), which can be an arduous task. Alternatively, the existing walls can be destroyed using explosives.
- At depths below zero, the backdrop of the map is generally no longer covered with actual wall tiles, though this can be difficult to differentiate visually since the biome background at these depths can have a similar appearance. Walls can be placed freely here by players.
- Torches and several other furniture items can be placed directly on background walls without requiring blocks below them.
- Most walls have no coin value, even if they were crafted from rare materials. Stained glass and wallpaper bought from the Painter are exceptions.
- Walls appear to have their own placement layer.
- Desktop 188.8.131.52: Made several wall types craftable that were previously unobtainable through the use of Ecto Mist.
- Desktop 1.3.1: Most wall inventory sprites updated. Which ones were not are currently unknown.
- Desktop 184.108.40.206:
- Living leaf walls are valid for housing
- Desktop 220.127.116.11: Fixed walls not framing properly in camera mode snapshots.
- Desktop 18.104.22.168:
- Bug fixed: The Blue Slab Wall is now valid for housing if placed by a player.
- Added Honeyfall, Granite, Smooth Granite, Marble, Smooth Marble, Chlorophyte Brick, Shroomite Plating, Martian Conduit, Luminite Brick, Meteorite Brick, and Crimtane Brick walls.
- Many naturally generated walls have a new appearance.
- Now you can place walls in front of each other.
- Desktop 22.214.171.124:
- Desktop 1.2.4:
- Adding walls made from Gemspark Blocks, Palm Wood, Boreal Wood, 1.2.3-Heavy Work Bench-products, and Glass+Confetti.
- The Pirate now sells the Sail.
- Two natural cave walls (7 and 8) have been added. Gemstone Cave- and Moss Cave-walls have received an overhaul.
- The Metal Fence has been split into Lead and Iron variants.
- The Lavafall Wall and Waterfall Wall are now crafted like most other walls.
- Painted walls show up properly on the map.
- Desktop 1.2.3: Adding Dynasty Walls, Lavafall Wall, Waterfall Wall, even more Wallpaper, and the Portable Cement Mixer for even heftier wall placing.
- Desktop 1.2.2: Ten new holiday-themed wall types called Wallpaper can now be purchased from the Painter.
- Desktop 1.2.1: Fixed an issue causing walls to not have different frames. Pumpkin Wall, Hay Wall, and Spooky Wood Wall added.
- Desktop 126.96.36.199:
- Lihzahrd Wall added.
- You can now craft living wood walls.
- Snow particles will no longer spawn on backwalls.
- Desktop 1.2:
- Desktop 1.1: Added Glass Wall, Planked Wall, Mythril Brick Wall, Cobalt Brick Wall, Mudstone Brick Wall, Iridescent Brick Wall and Pearlstone Brick Wall.
- Desktop 188.8.131.52: Walls that are automatically placed to fill small gaps are now correctly taken from the player’s Inventory.
- Desktop 1.0.6: When placing background walls, one-block holes are now automatically filled in.