English to Italian Law/Patents Real Estate

PROPERTY DETAILS
Small house located at ... (no street number) in ..., built on two levels (basement and mezzanine floors, registered as first floor below street level and ground floor) not interconnected, with surrounding exclusively appurtenant outdoor courtyard, as follows:
- a residential property unit occupying the entire mezzanine floor (registered as ground floor), consisting of a front porch, entranceway, living room, kitchen, hallway, two bedrooms and a bathroom;
- a property unit for storage use occupying the entire basement floor (registered as first floor below street level), consisting of a larger and smaller room, each with independent access from the common courtyard, with a total registered surface area of ninety-two square meters (92 m2).

In particolare non comprendo il significato del termine appurtenant.