In the years since Skara Brae re-emerged from the sand, one of the most commonly asked questions has been how were these Neolithic structures roofed.
Because nothing survived of the Skara Brae roofs, we must assume that they were made of a perishable, organic material — whalebone or driftwood beams supporting a roof of turf, skins, thatched seaweed or straw.
But out on the Ness of Brodgar, the archaeologists found Orkney’s first real evidence of a Neolithic roof.
In most reconstructions of prehistoric buildings, you’ll often see hotch-potched arrangements of turf, animal skins or perhaps thatch. But on the Ness, the Neolithic builders used stone slates for at least some of their buildings. One of these was Structure Eight, where the roofing remains were uncovered within the side recesses along the interior walls.
Site director, Nick Card, explained in 2010: “In the Structure Eight recesses, when we removed the upper layers of rubble, we found large, flat stone slabs, most of which would appear to be a standard thickness.
“Most of these thin slabs have been carefully shaped, with the edges trimmed to form regular, rectangular ‘slates.’”
Are we seeing the first evidence for a “standard” roofing system? Perhaps not for structures such as those at Skara Brae — in Structure Eight the excavators only found evidence for stone slates being used in the side recesses.
Nick said: “We may find other evidence as we dig, but perhaps this technique was only used to roof the side recesses as the limited span across these spaces would have made it quite easy.”
With no evidence of post holes inside the structure, it seems likely that a wooden framework was secured to the top of the building’s walls, and the slates attached to it.
Nick added: “Mixed in with the ‘slates’ are also some deposits of clay – was this used to calk the spaces between the slates to stop water ingress? Or possibly to bed the slates down on so as to achieve a more regular profile for the roof?”
Every “slate” is being carefully removed in sequence, numbered, measured and recorded so that the experts can not only piece together how they were used but also the way that the roof collapsed.