Nehemiah had earlier mentioned that the temple servants
lived on Ophel
(Nehemiah 3:26). So either there were more temple servants living not on Ophel but in a house strictly for temple servants or there was a separate house for these servants near their place of employment in the temple. The latter makes more sense since a) the piece of wall presently being described is in the vicinity of the temple (Nehemiah has nearly completed his circumscription of the city); b) Nehemiah adds that merchants
also used this house. That they would join the temple servants
in this house is understandable since they supplied the temple (no doubt via the servants) with needed supplies.
31 After him Malchijah, one of the goldsmiths, repaired as far as the house of the temple servants and of the merchants, opposite the Muster Gate, and to the upper chamber of the corner.