Monster Spawn areas

[Nagisa]

Do the monster spawn areas have some comditions?
Exampole giving: no light, no floor made of building blocks under the floor made out of the spawnblocks, at least x times x areas or something like this

[TheRemyD]

Each mob has their own specific likes and dislikes, but typically if you build a 18x5x18 room you should start seeing mobs spawning. The floor material needs to be the materials you would find where that creature typically spawns in the world.

[Nagisa]

...it worked til i build in a door. why doesnt the spawnarea work, when a door is build in?

[TheRemyD]

Although I do not have a solid answer for that, as it would take some serious testing, it may be a form of occlusion. Meaning that if an area is completely sealed then that area is treated as not a primary space for mobs. Instead of a solid door you could try mineral water to block the mobs into the room. This is only a temporary fix, but it may increase the spawn rate for you. Once again I do not know this for sure, but someone else also had this issue with spawners... I think it was Xent.

[beddtaliesin]

I build dungeons so it all depends on how big you want it. I usually do a small chamber, 7x7 that has the walls, floors and ceiling be the source material, eg peakstone. I leave a 3 block opening on one side and use iron bars. Iron bars work the best because I've found that, depending on how you build, you'll be able to hit the mob but they can't hit you.

http://steamcommunity.com/sharedfiles/filedetails/?id=576428276

This is my old dungeon that I did for lava and corruption layer. it is tiny and still spawned mobs like no one's business. I'd also get chests and keepas every once in a while too. As long as you don't use a 'bright' light source (right now the xmas lights seem to be the best), you can easily start farming. Basically, as long as there is a block space they can spawn in, they'll spawn. If you are after chests and mobs, go bigger.