i got this error when i try to build it
warning W073: removed block 447 - plane too narrow
and before it start to build it worm me that there are untexture block, which i have texture all the block.
anyone know what is the problem?

block 447 is one of my room floor.
i even got this kind of problem when i put light that under prefab into my level.

if i dont bother about the error, after build i run it, the level have no texture on. furniture not in and stair is not at the position i put.