The coastguard addition measures 7.88 metres in length, rises to two storeys with gable ends, and has a run of outhouses attached at its northern end. It is a quietly functional arrangement, one building leaning into another, each belonging to a different chapter of coastal surveillance.

The signal tower came first. Along the Irish coastline, these towers were constructed in the early nineteenth century as part of a network intended to relay visual signals rapidly between stations, primarily as a response to the threat of Napoleonic invasion. Coastguard stations, by contrast, were later additions to the coastal infrastructure, serving the more routine but no less serious work of preventing smuggling, assisting vessels in distress, and keeping watch over shipping movements. At Gortacrossig, the decision to attach the coastguard building directly to the existing tower rather than construct something freestanding produced an unusual hybrid: a working administrative and residential structure grafted onto what had originally been a purely military communications post. The outhouses to the north suggest a working establishment of some scale, with the practical needs of a small stationed crew taken into account.