How can I defend my home against hallow/corruption in hard mode?

I'm reasonably close to the point where I would try to trigger hard mode, and I'm making some preparations. As far as I understand, once I trigger hard mode, corruption and hallow will spread quickly.

I'd like to prevent my home base from becomnig corrupted/hallowed, what do I have to do to ensure that? I've created an air gap around the home, but is that enough? From what I read there are also enemies that can spread corruption, how can I prevent those from infecting my home?

Solution 1:

The Corruption/Crimson spreads much more easily in Hardmode, with the Hallow spreading in a similar fashion.

• Corruption, Crimson and Hallow will spread to stone, sand, ice and dirt that are up to three tiles away.
• Almost all other blocks are immune to Corruption and Hallow, including Wood, Clay Blocks, Ash Blocks, Silt Blocks, Obsidian, Ores, Gems, and all bricks (except Pearlstone, which will spread Hallow).
• Corruption and Crimson can convert mud blocks into dirt over time. Mud blocks containing mushroom grass are not affected.
• Sunflowers will no longer prevent the spread of corruption. Instead, they will pop out of the ground as corruption spreads past.
• Hallow and Corruption cannot convert each other.

There are no longer enemies that spread corruption, crimson, or hallow. So, what you need is a 4 tile barrier made of pretty much anything besides stone, sand, ice or dirt. The favored method is by making a quarantine tunnel all the way around you base. My preferred method is as follows:

1. Start with a 4 block wide tunnel. You can use the Ruler if you're super paranoid.

   

2. While that tunnel itself is perfectly fine for hardmode protection, I like to line my tunnels with Some type of brick. This has multiple advantages such as thorns no growing in your tunnel (since the corruption can't spread over the bricks themselves), it looks nice and clean, and most importantly, it is a visual reminder to you and other players not to build there. Keep in mind that these bricks are in addition to the 4 air tiles

   

3. Now just continue with this tunnel all around you base. Give yourself plenty of room so you can keep your farms within the quarantine zone and so you don't have those hardmode enemies spawning right at you doorstep.

   

Solution 2:

An air gap of a width of at least 4 blocks should work fine.

Blocks that are up to three squares away from an existing corrupt block can be converted (even if uncorruptible blocks are in the way).

^source

However, thorns (also known as thorny bushes) may grow upwards from the corruption and get to your house. To prevent this, you could either fill the air gap with a barrier of uncorruptable material, or make the air gap larger and watch the thorns to make sure they don't grow too far.

The enemy that used to spread corruption no longer spreads it, so you don't need to wrory about that.

Personally, my house is floating about 50 blocks in the air. It seems to be working fine; the thorns can't really grow that high so I don't even need to watch out for those.