block of flats’ communal garden

[Quang Hai]

I am reading W. Trevor. short-story.
'Yes, that key had been Margy’s, Francesca said. Left for her under a stone at the foot of a hydrangea bush in Pimlico, in a block of flats’ communal garden: she didn’t add that'

Please could someone help me out in meaning of the underlined words. Thanks.

[SoothingDave]

Which word is giving you trouble?

Apparently, there is an open area in the middle of a group of apartment buildings.

[bhaisahab]

I am reading W. Trevor. short-story.
'Yes, that key had been Margy’s, Francesca said. Left for her under a stone at the foot of a hydrangea bush in Pimlico, in a block of flats’ communal garden: she didn’t add that'

Please could someone help me out in meaning of the underlined words. Thanks.

A garden shared by the residents of a block of flats (apartment block).

[5jj]

Quang Hai's difficulty may be with the placing of the apostrophe. Such phrases as those I have written below are correct in English, but may seem strange to learners. It's the word I have put in bold, not the one with the 's, that is the 'possessor':

The King of Spain's daughter ....
The President of America's wife ...
The block of flat's garden ...

There can sometimes be ambiguity:The sister of my neighbour's husband is sloppy. It could mean The sister of [my neighbour's husband] or [The sister of my neighbour]'s husband