The most obvious remains of potential Iron Age settlement outside of enclosures are hut-circles and platform sites. The majority of hut-circles comprise a single circular or sub-circular wall ring, which can be constructed from earth or stone or more likely a mixture of both. The RCAHMS in its compilation of the Argyll inventories noted that many hut circles were likely associated with relic field systems such as those recorded at Druim Mór (NMRS No. NR38NE 13) on Oronsay, which were defined by a series of earthen dykes (RCAHMS 1984). The few hut circles that have been excavated show that these structures originate in the 2nd millennium BC and can continue in use until the 1st millennium BC (Stevenson 1984; Ritchie 1997). However, it does seem highly probable that some hut circles belong to a later period and recently what is probably Iron Age pottery was recovered from the evaluation of two hut circles at Beinn Bheag (NMRS No. NR49NW 56) on Colonsay, although these sites await radiocarbon dating (Regan 2012b).
Less easy or impossible to discern as earthworks are the remains of timber post built roundhouses, which may originally have had upstanding remains, these subsequently the victim of later agriculture or settlement activity. The remains of two roundhouses were excavated on Tiree in the early 20th century at Corniag and Balevullin (NMRS No. NL94NE 6) (Beveridge 1903; Mann 1906; MacKie 1963a). Other Iron Age roundhouses have been uncovered at Ardnadam (12m- 12.5m dia.) and Bruach an Druimein (7.5m-10m dia., NMRS No. NR89NW 11), the later dating to the 4th – 1st centuries BC (Rennie 1984, Abernethy 2008). Recently a large early Iron Age roundhouse structure (14m dia.) was uncovered at Glennshellach and another roundhouse structure (9m dia.) was excavated at Midross (CANMORE ID 281530) (Ellis pers. comm.; Maguire, Becket and Rennie 2005). What seems increasingly likely to be a roundhouse platform has been partially excavated at Carnassarie, producing pottery and midden deposits dating to the 4th – 2nd centuries BC (Ellis 2008). Groups of roundhouses have also recently been excavated at Dunbeg and Glennshellach, mainly dating from the middle Bronze Age although one dates to the early Iron Age and these will significantly add to our understanding of this type of structure in Argyll (see also Case Study 4: Dunbeg and Glenshellach and Ellis 2013). The roundhouses at Bruach an Druimein, Ardnadam and Glennshellach are located in areas that also have evidence of occupation from other periods perhaps hinting at settlement continuity. This also appears to be the case at the sites at Ardnave (NMRS No. NR27SE 22), Achnasavil (NMRS No. NR73NE 9), Killellen (NMRS No. NR27SE 3) and Kilninian which also have evidence of Iron Age occupation amongst that of other periods (Ritchie and Welfare 1984; Siggins and Carter 1994; Ritchie 2005, Ellis pers. comm.).