log cabin cant be placed 2 tiles to the east of a small house and probably other types. west side no problem. place the log cabin first and place a small 2 tiles to the west of the cabin no problem. other way around? go fuck yourself. i ran into a similar issue months ago with 2 small houses but it was a z-axis issue where a small house couldn't be placed next another if it didn't go down first.
The roof tiles of certain small houses overhangs 1 tile outside the foundation resulting in houses attempting to be placed close by requiring an additional 1 tile of space between the houses. This is a known issue and has an open bug report.