hedging

hi am looking for some advice. there is a small strip of grass between the side of my house and next door. i would like to plant a hedge and went digging there today but about six inches down i was met by concrete. the strip of grass as my photo shows is between two footpaths. . i had intended to plant Portuguese laurel but six inches down is not enough root space. has anybody any suggestions as to hedging plants with small root requirements. i have thought about box hedging but wonder if it will do well. i have some plants and they have tiny roots but wonder if they will need much more space as they grow older. also the area is quite shaded.