How can I obtain the urban mask without bare soil?

I need your help. I try to mask the urban area from Sentinel-1A IW SLC data using following tutorial
I calculated the interferometric coherence and the average backscatter from two SLC datasets ( 31 october and 24 november), but in the urban mask obtained the bare soil is mixing up with the urban area. The bare soil coherence and the backscatter intensity is similar with the urban area. How can I remove the bare soil? I want to obtain the urban mask without bare soil!
Thank you in advance!

did you have a look at the forum of this course? The tutorials are discussed there quite a lot.