Type 1: Turf wall (and roofing) | Wall built of turf blocks, directly on the ground or, more commonly, on a single- or double row stone foundation of one or a couple of courses, often with some soil/rubble/turf filling. Wall width(s) normally >0.80 m. | Well preserved: grassy banks tracing the original feature wall lines; or, where the turf has disintegrated, as a distinct stone foundation of one or a couple of courses, and with no surrounding collapse stone. Collapsed: grassy, uneven(farm) mounds or low hummocks. No or very few visible collapse stone. | Heat insulating, water, wind, and moisture impermeable. Built for cold-period (or year-round) human and animal habitation. |
Type 2: Turf/stone wall | Wall built in relatively regular, alternating layers of turf blocks and stones, raised on (rarely) single- or (often) double row stone foundation of one or a couple of courses. Wall width(s) normally ~0.6–1.0 m. | Well preserved: easily traceable walls of stones set in turf and often preserved in several courses. Collapsed: indistinct stone wall lines, sporadically standing a few courses high,and raised on single- or double-row stone foundations; or as grassy (farm) mounds or low hummocks many protruding stones. Considerable amounts of visible collapse stone. | Turf is economical and stable, but less heat insulating and water, wind, and moisture impermeable than Type 1 walls. Built for seasonal warm-period human and year-round animal habitation. |
Type 3: Dry-stone walls | Can be separated on following subtypes: | |
3a. Freestanding single-skin dry-stone wall | Dry-stone walls built in often somewhat irregular courses/layers, at times with thin interlaying turf mats and turf wall superstructure, either directly on the ground or on a single row stone foundation. Wall width(s) normally 0.5–8.0 m. | Well preserved: distinct stone walls, often including natural boulders or cliffs, and preserved in several, often irregular, courses. Collapsed: indistinct, but identifiable walls of collapse stone, most sliding or tumbling down the stones, boulders or cliffs in the foundation. Some to considerable amounts of visible collapse stone. | Expediently and easily procured building materials, partly sheltering, but heat draining. Used in pens, dikes, and other freestanding enclosure walls (e.g., pens, rock shelters, etc.). |
3b. Dry-stone wall facing | Dry-stone wall built in mostly regular courses/layers with no adhesive or, alternatively, with thin interlaying turf mats, against and to support/protect the interior or/and exterior of a turf wall (Type 1 or 2). Wall width(s) normally ~0.4–6.0 m. | Well preserved: distinctstone walls in several regular courses lining a Type 1 or 2 turf wall. Collapsed: more or less indistinct stone wall lines leaning against turfy banks, sporadically standing a few courses high, and inward/outward sliding collapse stone.Considerable visible collapse stone, most on one side of turf bank. | Expediently and easily procured building materials, wind- and water protective and durable. Built for protection of insulating turf walls (i.e., increased stability and durability of human and animal habitation buildings). |
3c. Roof-supporting dry-stone double-skin wall (double dike) | Dry-stone double-skin wall built mostly in regular courses/layers with no adhesive, and at least one of the following traits: i) alternating thicker and thinner courses; ii) larger stones in the lower courses; iii) heavy foundation and, especially, corner stones; iv) stone wedges/pinning to level uneven stones in the courses; v) hearting with small to medium sized stones Wall width(s) normally ~0.8–1.0 m. | Well preserved: distinctdouble-skin walls standing almost intact (see description) with few surrounding collapse stone. Collapsed: faintly observable double-row wall foundations or lines standing up to a few stone courses high and surrounded by great amounts of collapse stone. | Expediently and easily procured building materials, ventilated and cool, highly stable and durable. Built for airdrying and storage. Occasionally used in freestanding boundaries or enclosure walls. |
3d. Roof-supporting drystone double-skin wall with (double dike) fill or hearting | Dry-stone walls with all the elements of Type 3c, but with fill/hearting of the double-skin wall with small stones and rubble, occasionally some turf lumps, soil or gravel. Wall width(s) normally ~0.8–1.2 m. | Well preserved: distinctdouble-skin walls standing almost intact (see description). Collapsed: faintly observable double-row wall foundations or lines standing up to a few stone courses highand surrounded by great amounts of collapse stone. | Expediently and easily procured building materials, somewhat ventilated and water impermeable, cool, highly stable and durable. Built for storage. |
3e. Protective dry-stone (and turf) wall with fill or hearting | Similar to Type 3d or with alternating courses of stone and thinner turf mats. Occasionally built to the height of the inner, roof-supporting wall, but more often with a superstructure of pure turf wall (Type 1). | Same as Type 3d, but with considerably less collapse stone, often spilling outwards from the building. | Built as a weather protective, water- and wind-impermeable casing of/shell for a wooden inner structure/building. |
4: Wooden wall | Wooden wall raised on single row dry-stone foundation/sill. Wall width(s) normally 0.3–0.5 m. | Visible as single row dry-stone foundations with no surrounding collapse stones. | Ventilated. Built for airdrying and storage. |