When I was in England many years ago I saw some houses with only HAY on the roof. It made a poor roof.
It's not 'hay', it's 'thatch'
It's also a VERY old roofing style - and even so it's not that 'poor' a roof, with a life expectancy of over 50 years.
While most thatched properties are older than Canada, apparently it's become popular on some modern highly expensive houses, purely for aesthetic reasons.
But thatched properties are really very rare, with most such old buildings having modern slate or tile roofs fitted - until the buildings got 'listed' and you weren't allowed to replace the thatch.