There's a bit of irony there - when I first heard the term Petty Dwarves I laughed (and I admit it still raises a snigger) as the Petty is the toilet where I grew up.
And most British terraced houses still have outhouses. They also have indoor toilets nowadays but the outhouse remains as a handy 'extra' - or at least somewhere secure to store the Barbecue and garden chairs!