A number of people have been experiencing issues with NPC Housing since Patch 1.1 came out. In particular, it has been noted that the "This housing is not suitable" message can appear in cases where players have met all of the usual housing requirements from the previous patch. This has spurred me to perform some testing to try to determine exactly how the NPC Housing requirements have changed. I have come across some very interesting results which I wish to document here. Once enough testing has been performed, I hope that my efforts can be used to bring the Housing page up to date for Patch 1.1. Edit: Retesting has shown that every concept on this page carries over to the Christmas Update (Patch 1.1.1) as well.


Throughout this blog post, I shall use the word "suitable" when referring to a house that, when queried, returns the "This housing is suitable" message. I shall use the phrase "NPC-valid" to refer to a house that has a visible NPC flag within it after an NPC has been assigned to that house. Note that these two concepts are related, yet distinct.


  • NPC-valid houses still require a comfort item, a flat surface item, a light source and background walls, just like in older patches. We all know this.
  • NPC-valid houses usually require background walls that have been been placed by the player, however, the world-generated backgrounds walls in an Underground House and in the treasure room of a sky island are two exceptions to this rule. See subsection 11 for explanation.
  • NPC-valid houses do not require a door, strictly speaking. They require an entrance, which could be a door, but it could also be a wood platform. Whether or not the player can fit through this entrance is irrelevant. In fact, it could even consist of a single wood platform in the ceiling or the floor (tested but not shown in the pictures). See subsection 7 for explanation.
  • Two NPC-valid houses are allowed to share a single entrance. See subsection 11 for explanation.
  • NPC-valid houses must have a floor that has at least one solid block for the NPC to stand on at night. This so-called "NPC Block" must be adjacent to or one block away from either a comfort item or a flat surface item within the house. Additionally, there must be 3 or more blocks of empty space above this "NPC Block." See subsections 3, 4, 5, 6 and 9 for explanation.
  • NPC-valid houses cannot have too much corruption too close to them. A maximum of 49 corruption blocks within a distance of 42 blocks from the house are allowed, this distance being measured from the outermost point of the house to the corruption-type block (ebonstone, ebonsand, dirt + corrupt grass) in question. The presence of additional corruption blocks 43+ blocks away from the house doesn't matter, but 50+ corruption blocks within the 42 block distance is not allowed. These numbers may not be 100% reliable, as extensive testing shows, but they do give an good idea of how much corruption is "too much" and how close is "too close." See subsections 8, 10 and 11 for explanation.

1) The Funhouse


Home is where the heart is.

After an hour of messing around, I was able to construct a very odd house which is both "suitable" and "NPC-valid," as proven by the flag in the picture and the messages in the bottom left corner. Please take a close look at the picture above and observe the following:

  • This house uses a Bed for its comfort item, a Work Bench for its flat surface item, and a Torch to meet its lighting requirement.
  • This house does not possess a single Door. In previous patches, NPC houses always required a door.
  • This house has a ton of Wood Platforms as part of its floor and roof. You can do that!?
  • This house uses Active Stone Blocks on the left portion of its wall.
  • This house uses Ebonstone Blocks as its right wall, which is rather interesting.
  • This house has 1 solid block in its floor. This is apparently very important, as I shall attempt to demonstrate.
  • There are a series of measuring blocks outside the left wall and below the floor, so that the size of the house can be measured and my test steps can be reproduced.

2) Just Checking...


Inactive Stone Blocks cannot be used as walls. This means that they cannot replace the function of Doors. Well that's good to know I guess.

3) What's So Important About That One Block?


In this picture, the floor of my house is made entirely of wood platforms and it is not "NPC-valid."

The only difference between this picture and the first one is that I have replaced the solid block on the floor with a wood platform. It turns out that this house is still "suitable," but it is not NPC-valid! When I clicked on the dryad's portrait and tried to assign her to the house, her flag absolutely refused to appear in the house and she would not move in at all. I can't explicitly demonstrate that in the photo, but that's what happened. I challenge anyone who doesn't believe me to try to build house with a floor consisting of entirely wood platforms.

Conclusion: Apparently the floor needs to have at least one solid block.

4) Ummm... What?


A house that is not "NPC-valid." But all I did was move the work bench!

The only difference between this picture and the first one is that I have moved the work bench one square to the left. Lo-and-behold, the house is still "suitable," but it is not "NPC-valid." I tried to assign various NPCs to the house, but it didn't work and the flag didn't appear, despite the fact that the solid block is still there.

Question: Why is the house not "NPC-valid" when the only thing I did was move the work bench one square over?

5) I Think I Get It


This picture demonstrates that NPCs require at least one solid block to stand on.

Hmmmm, some NPCs teleported to my house while I was away. Now then, to produce this picture, I started with my original house in the first picture, and just moved the work bench over to the right side to get it out of the way, and then I placed the bed adjacent to the solid block. Bingo! I am able to set my spawn point, the house is "suitable," and it's also "NPC-valid," as you can clearly see by the flag on the screen and the messages in the bottom left corner.

Conclusion: NPCs require at least one solid block to stand on, and this solid block must be nearby either a comfort item or a flat surface item within the house. The reason for this is because NPCs have an AI which tells them to stand still next to one of these objects at nighttime.

6) Make Room For My Hair!


In this picture, I have placed a single stone block above where the NPC would stand at night. Apparently that won't fly, because this is another case where the house is "suitable" but not "NPC-valid."

Conclusion: The NPC requires 4 blocks of vertical space in order to stand still at night.

7) Where's The Entrance?


This picture demonstrates the technicalities of an entrance. Here the floor is counting as entrance, even though it's not accessible.

Before now, there has only been one usable entrance to the house: by dropping down through the wood platforms that form the roof. I have now replaced those wood platforms with solid blocks, so that there is no longer a usable entrance to the house. That's not a problem, as this picture demonstrates. The reason this works is because the floor still counts as an entrance, even though it's technically blocked off.

Conclusion: Houses in Patch 1.1 don't require doors. Wood platforms can also count as an entrance.

(Thanks to Jigokuro for catching a mistake in this section)

8) Let's Talk About The Corruption


Here is an "NPC-valid" house near some corruption.


Too much corruption causes the house to not be "suitable."

To put it simply, if too much Corruption is too close to an NPC House, then it will be neither "suitable" nor "NPC-valid." I feel that many players are generally aware of this issue, but I want to very explicit about the fact that it's not just the closeness of the corruption that matters, it's also the quantity. In the first picture, you can see that I have constructed a "suitable" and "NPC-valid" house with the apparent maximum allowable amount (89 blocks) of Corruption ridiculously close to it, so close in fact, that all of my walls are literally made of Ebonstone. The second picture shows that placing a 90th Corruption-type block (it's actually ebonsand) near my house (look in the upper right corner) causes it to become unsuitable.

Edit: The 89 block quantity limit is slightly contradicted by findings that I made later in a 1.1.1 world, please read subsection 11 for explanation.

9) Patch 1.1.1 Small Difference?


Compare this picture to the one in subsection 4. Possible difference between patch 1.1 and 1.1.1??

Now that Patch 1.1.1 is out, I was running through some quick retesting when something caught my eye. My house here is both "suitable" and "NPC-valid," but I was able to get 1 extra blocks-worth of horizontal distance between my flat surface item and the block on which the NPC will stand at night. Also, I think I forgot to mention it before, but the flag indicates where that block is. After replacing that one ebonstone block which the flag is floating over with a wood platform, my house was no longer "suitable."

10) Let's Talk About The Corruption Again


My house is not "suitable" because the corruption is too close.


Moving the offending piece of ebonstone over one square fixes the issue.

As I pointed out before, the distance between your house and the corruption is just as important as the quantity. In the picture above, my house is once again not "suitable" because there is too much corruption too close. In this case, the key point is the Ebonstone block which is 42 blocks east of the eastern wall of my house. The picture below demonstrates that moving it over one square allows the house to be "suitable" and "NPC-valid" again.

Note: I also tested this 42 block distance concept to the north of my house's northernmost roof and it applied as well, though I won't post pictures for it.

Conclusion: "Suitable, NPC-valid" houses cannot have too much corruption (90 blocks in quantity) too close (within a distance of 42 blocks from the outermost wall of the house) to them.

11) Additional Notes

I have more photos, but this article is so bogged down that I don't want to upload any more, so I'll just summarize some more findings in writing. Edit: I've included one last photo at the bottom that validates various claims made in this section.

  • Testing in another 1.1 world over the ocean was able to reproduce the 89 block quantity, 42 block distance result with respect to the corruption.
  • Testing in a brand new 1.1.1 world with a house at the top of the world showed that the 42 block distance still holds true in 1.1.1, however, the presence of a 50th corruption block caused the house to no longer be "NPC-valid," whereas it was "NPC-valid" when there were only 49 corruption blocks.
  • I also tested this in a different 1.1.1 world with a house over the ocean and reached the same result of 49 quantity, 42 distance. I will have to change the 89 block quantity limit to a 49 block quantity limit to be safe.
  • This may not be too surprising, but I was able to show that "NPC-valid" houses do not always require player-placed background walls. For example, the world-generated background walls in an Underground House and in the treasure room of a sky island can be used to create a "suitable" and "NPC-valid" house. These are just 2 special cases though. In general, background walls must be placed, not world generated.
  • Additional testing in a new 1.1.1 world has demonstrated that it is possible to construct an "NPC-valid" house where the NPC block has a tiki torch placed on top of it. Also, it is possible for the NPC block to only have 3 blocks of empty space above it, rather than the 4 that I originally discovered while testing in 1.1.
  • It is possible for two NPC houses to share an entrance! I feel very stupid for neglecting to test this earlier.
  • An "NPC-valid" house can have wood platforms for its side walls (which may also count as an entrance), in addition to the floor and roof. In fact, I have constructed several houses using only wood platforms for all of the walls, with the exception of one solid block in the floor to meet the NPC block requirement.


Thanks For Reading =)

I hope that this blog entry was informative. I challenge anyone who is interested or who doesn't believe my claims to test this for themselves. I will hopefully be updating the Housing page soon. Well, that's all I have to say for now, so, have fun fellow Terrarians!