Why won't an NPC go into his house?

If your demolitionist has claimed a room offscreen, you may need to go far enough away that he teleports 'home'. He's not going anywhere because he can't reach his house in the first place.

Kill demolitionist with lava. Then he will respawn after some time. And maybe he will choose more desirable place :-)

When NPC begin to live in house not suited for him, I kill NPC and destroy chair and table. And in next time NPC chooses another house :-) After that I place taken off object on their place.

P.S. Magma is a solution for every problem :-)

magma or get a voodoo doll. which allows you to kill NPC's.. gained by killing a voodoo daemon

If you've already set the NPC's flag to the house you made, when night falls, try to avoid having the NPC and its designated house on the screen.

For me, the issue was the middle of the room was too dark, so I just added more torches.

For some reason, It will say that its suitable instead of saying it needs light source.

If you are trying to get the demolisionist to move into a house which is on an upper floor, I find the easiest thing to do is to build a wooden PLATFORM staircase up to his room. You can make this go as high as you want. You will need a background wall too by the way. If he simply won't move into any house, lower floor or upper floor then the room either isn't valid (in which case you will need to make sure all the walls are filled in, there is a table, chair and torch. You can check if a room is valid by checking in the housing menu) or he legit can't reach his house, in this case you will have to make it easy for him to reach.

you can go to your inventory and click the pixelated picture of a house and click an N.P.C, then click on the house you want him or her to go to, but before doing that, build another home for the N.P.C who's living in the house and move them to that empty house if there is one living there. If not, make sure that everything that is needed for a house to be a real house, here's what you need: 1.A Door 2.A Table 3.A Chair (or two) 4.And a Light source. (Like a Torch or a chandler, or a lamp)

NPCs can't jump more then 3 blocks and don't know how to use platforms/ropes (they can use platforms if they are converted to stairs)! The second floor of the guide house (blue) is more then 3 blocks high from the ground! He will be automatic teleported to the house on the next night.

Houses cannot contain platforms for floors, making it an invalid house. Also, there cannot be holes in the walls or floor. A door cannot be placed on platforms, either. Put a door on the right the platforms to make it a valid house.