forget 20th century norms!
The last old houses in Gt Nelson street were pulled down about 10 years ago - they were built from manx slate rubble walls plastered over inside and rendered outside (walls looked about 2 ft thick - these houses had two floors - the toilets would originally have been outside - piped water possibly not in 1860 as that was only being introduced to poorer areas from 1850's though these being in centre of town might have been connected - most likely a family had one room - not sure re kitchen