Yet more lurking

The builders discovered that the shrub bed below the window of the room being converted into an accessible bathroom was surprisingly shallow.

I've cleared this so far. Conservatory floor? But it is at the north-eadylt corner of the house.

A fernery? They were all the rage in the 1850s-70s i think.

A patio from which to observe games of croquet?

We may never know, but i intend to try.