Interesting... I always thought "semi-detached" implied "detached above ground, but not below ground", essentially what the Wikipedia article called "linked" homes.

Do you actually have a common wall between the houses above ground ?

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8