Skara Brae and Neolithic Orkney Roofs

Skara Brae is a Neolithic village on the Bay of Skaill in Orkney, Scotland, occupied from about 3180 to 2500 BCE. A severe storm in the winter of 1850 stripped earth from a mound and exposed the outlines of several roofless stone houses. Their stone walls and furniture survive remarkably well, but the roofs do not, and how they were covered has been debated for a century. Skara Brae is part of the Heart of Neolithic Orkney World Heritage Site, inscribed in 1999.

The village

Ten structures and four passageways are visible. Seven houses share a similar arrangement of stone furniture, and drains run under at least five. House 8 stands apart, with walls over 2 m (6.6 ft) thick and a porch.

Roofing theories

• Perishable roofs: because nothing obvious survived, roofs were long assumed to be of whalebone or timber beams covered with turf, skins, seaweed thatch or straw. Whalebone does occur at the site, though as tools and beads, and driftwood is thought to have been burned as fuel.
• Corbelled stone: after excavating in 1929-1930, V. Gordon Childe considered beehive-like corbelled roofs, but there was not enough rubble to have covered the full span.
• Stone slabs: Childe also recorded thin slates on top of floor flagstones that broke underfoot, and broken slates among bone and shell on the floor of House 7. At Rinyo on Rousay in 1938, excavators found a layer of thin slabs on floors and interpreted it as a collapsed roof. These observations were largely overlooked.

The Ness of Brodgar evidence

In 2010, excavators at the Ness of Brodgar found what they describe as Orkney's first real evidence of a Neolithic roof, in Structure Eight. Trimmed rectangular sandstone slabs lay on the floor deposits and were first taken for paving. Similar tiles were later found in Structures One, Ten, Twelve and Twenty-Seven.

• Size: 38-57 cm (15-22 in) long, 23-40 cm (9-16 in) wide and 1.3-2.7 cm (0.5-1 in) thick.
• Fixing: none had peg holes. The slabs were probably laid on a timber frame, largest at the eaves and smallest near the ridge, held by their own weight and perhaps bedded or sealed with white clay found among them.
• Frame: no internal post holes were found, so the frame probably rested on the wall tops. One calculation put the ridge up to about 4 m (13 ft) above the wallhead, close to 6 m (20 ft) above ground.
• Collapse: the pattern of fallen slabs suggests one section of roof fell in a single event.

Not every Ness building was stone-roofed. The excavators suggest some Skara Brae houses may have been as well, though this remains a possibility rather than a demonstrated fact.

Continuity

Orcadian builders went on using stone slab roofs into the 20th century, so the Neolithic evidence connects with a long local tradition of flagstone roofing.