I wrote "pair of houses". That would be correct in English, but I am not familiar with the term semi-detached house.
If you translate it literally it is ‘a paired house’, which describes it pretty well - one of two houses built together as a pair, sharing a common central dividing wall. Usually called ‘a semi-detached house’ in Britain.
- a pair of houses - pâr o dai
Since "semi-detached" is not given as a possible meaning for "par" I think "a pair of houses" should be accepted, or else the meaning of "par" needs to be amended.