There are different types of groundsheets. the ones in my synthetic tents are polythylene, same as builders tarpaulins.
then there are heavyweight rubbery type ones you can get
some people use pondliners for groundsheets in canvas frame tents too.
basically they can be anything waterproof.
then there are also breathable ones in rubbery type material with holes for the grass to grow through, usually used in caravan awnings where sites say no other groundsheets except these can be used.
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets