While most of the medieval defensive domiciles in Lorn are called castles, it is useful to categorize them into four types: Castles, Keeps, Tower Houses and Hall Houses described below. A Glossary of Terms Explaining Structural Elements is provided after the Hall House section.

CASTLE 
Description – A rectangular enclosure of considerable size having halls, kitchens, and other accommodations built against the inside of the perimeter walls.
Examples – Innischonnell and Dunstaffnage are Castles, both taking the form of large rectangular enclosures containing halls, kitchens, and other accommodations built against the inside of the perimeter curtain walls. Advances in design over time led to rounded corner towers rather than the older style square towers. Dunstaffnage Castle shows the advanced design of rounded corner towers rather than the earlier style square towers of shallow projection seen at Innischonnell Castle.

KEEP
Description – A strong tower built within outworks. Another name for a Keep is “donjon.” Keeps feature a single tower with the kitchen, hall, and living quarters on successive vertical levels. Keeps usually had outworks, including a postern entrance and enclosed courtyard or bailey. Keeps were often built of stone and located on an eminence or motte, which was often artificially built up higher with excavated materials. In early stone castles the Keep was a standalone, often square, structure that could be defended. Over time these structures were improved upon and built around to make a larger and more complex structure.
Examples – Of the early Keeps in Lorn, Dunollie Castle is the most impressive in size and in construction.

TOWER HOUSE
Description – These were a simpler form of Keep, often built with a vaulted cellar at ground level and with the entrance on the second storey. Later constructions were much more ornamented. The Tower House design is really just a Hall House design stood on its end.
Examples – Dunollie Castle is a Tower House with a vaulted cellar and a mural fireplace in its hall. Later and more ornamented Tower Houses are represented by Gylen on the isle of Kerrera.

HALL HOUSE 
Description – A Hall House consisted of a public hall with private living accommodation attached. Such a building was called a Palace, an old Scottish term for the two-story hall block domestic building which was built from the medieval period onwards for a high-status person such as a Bishop or royalty. Such high-status buildings had some defensive fortifications but they were not military forts.The large fortified Hall House buildings built for MacDougall and MacDonald Chiefs at Ardtornish in Morvern, Aros on Mull, and Finlaggan on Islay were designed on a scale much larger than those of their followers. Their interior halls provided the large space required for the lavish feasting and entertainment expected of the chief men in a society which measured their social status by their generous and large entertainments.  The Hall House design met that need. By the end of the 14th C. the Hall House structure was nearly out of style was being replaced by the Tower House design which is really just a Hall House design stood on its end.
Examples – Achadun Castle on the Isle of Lismore is an example of a Hall House. The MacDougall Chief’s Hall House at Aros Castle on the Sound of Mull was the largest in Scotland. 

A GLOSSARY OF TERMS EXPLAINING STRUCTURAL ELEMENTS
Arrow Loops:
These were slots of various shapes and sizes in the walls and structures that defenders used to shoot arrows through. Gun ports later took their place.
Bailey:
The inner space enclosed by the outer wall of a castle. It can be called a courtyard. In Scotland only the most important castles had a Bailey.
Barmkin or Barmekin:
A small yard surrounded by a defensive wall. The small area protected by the wall at Dunollie is a Barmkin.
Curtain Wall:
The stone outer walls around a castle such as Innischonnell and Dunstaffnage.
Donjon:
An old word for a great tower or a Keep.
Dungeon:
A cell typically underneath a castle. The word is derived from the word Donjon.Log Out
Floors:
The first floor was supported upon the vaults of the cellar and usually paved with stone. The upper floors were made of wood resting on wooden joists running from wooden stringers along the walls that, in turn, rested on embedded corbels projecting out of the walls. In some cases such as Gylen, floor joists were mortised into the walls themselves.
Fosse:
A ditch or moat that restricts the enemy’s approach to the outer walls of a fortification. A Fosse may contain water.
Keep:
The main tower used as the last line of defense during siege or attack was called the Keep and it was usually the tallest and strongest structure in the castle.
Moat:
A type of Fosse. A Moat is a deep wide trench dug around a fortification and usually filled with water.
Mote or Motte:
A hill, often man-made with materials excavated from the fosse around it, to give added height to the buildings being constructed upon it. On some mottes, ring work fortifications were built. Their defensive structures were usually wooden until the advent of stone-built Keeps.
Mote Hill or Moot Hill:
A flat-top hill or an unfortified mound for courts of justice. The word “Mote” is believed to be from the Gaelic word mod meaning a council or court of justice.
Postern:
A secondary door or gate at the back or side.
Roofs:
The roofs were supported on timber frames, while the gables were of stone, often with the characteristic “crow step” construction which results in a stair-like appearance. Early roofs were covered with turf or timber, and many later ones with lead or slates.
Walls:
The thick walls of earlier Castles and Tower Houses were built of roughly coursed and unsquared sandstone. Corners and openings were dressed with squared blocks of sandstone. Door and window facings were often carved and chamfered. Portals, windows, embrasures, and passageways were either capped with large stone mantels or arched. At Dunstaffnage Castle some fine pointed arches are found. Gray-green sandstone from the Quarry of Ardentallan on the north shore of Loch Feochan was used to build the towers of Dunollie and Gylen Castles, and the Churches of Kilbride and Kilmore.