To be strictly correct, a riad should have a garden in the centre.
A classical riad has a pavilion at either end, a four quartered garden in the centre, and traditionally a water feature, a pond or fountain, in the centre.
The term has become very corrupted, and today anything with a central courtyard is a ‘riad’.
Smaller houses with central courtyards should simply be ‘dar’.
The Riad name became over used because of the popularity of guesthouses in the medina.
But to be a guesthouse (and have the right to rent room by room) you need permission – ‘Classement’ – as a maison d’hôtes.
This comes with a whole raft of ever increasing requirements, some negotiable, some not.
As a guide:
Minimum 120m2 footprint
Minimum 5 bedrooms of 17m² each
If a building has Classement or can get it values rise because the gross ROI increases, *but* so do operating costs and complexity…