An Introduction to Crannogs

At our recent members night David Hill sparked a great deal of interest when he spoke about a possible crannog that he had recently discovered in the Lee Estate. As I did not have a great deal of knowledge of the subject I have used the Web to put together a brief introduction to the subject.

The term Crannog refers to small artificial islands which can be found in the majority of Scotland’s lochs and inland waters. From the surface, most crannogs look like uninteresting mounds of stone, from which timbers sometimes protrude. These small islands were constructed and occasionally lived on by people, as recently as the 17th century. Most crannogs are to some extent artificial. This means that it has taken a certain amount of human activity to create them. In some cases, small islands or natural bedrock outcrops were only slightly enlarged, requiring relatively little effort. In other cases, crannogs were created from scratch by piling up vast amounts of materials on the loch bed. This obviously required substantial effort and considerable time. Regardless of the effort the product is always very similar- a small island, its surface protruding above the water surface, which owes its existence to human activity. Other features which are also found on crannogs include: approach causeways from the shore, vertical wooden piles set into the lochbed, middens of discarded domestic waste, harbours and jetties.

Crannogs can take a variety of forms. Most are circular or oval, but differ greatly in size. Average surface diameters range between 15 and 30 m, although there are notable exceptions both larger and smaller. The materials used to build Crannogs vary throughout Scotland. Crannogs found in the Hebrides seem to have been built primarily of stone whereas those found in mainland were predominantly built of wood. Most of this variation has been ascribed to differences in local environments. In general, people used materials which were easy to come by or immediately at hand.

Evidence suggests that Crannogs have been used as habitation sites for a period longer than any other type of structure in Scotland’s history. Literary evidence indicates that crannogs were still being used in remote areas of Scotland until the seventeenth century. Archaeological excavations have shown that crannogs were used during various periods ranging from Roman times (80-400 A.D.), the Bronze Age (2000-500 B.C.), and the Neolithic (4000-2000 B.C.) This extensive time range makes it very hard to know when a particular crannog was in use.

At the moment archaeologists believe that there are fundamentally two types of crannogs. One has a solid base and is literally an island. This is the type which most commonly survives, an Scottish example from Loch Cinneachan is shown above. The other type is a raised structure, such as a stilt house or large dock. This later type stood above the water and was substantially taller. A example of this type is the life-size reconstructed Crannog at the the Scottish Crannog Centre.

The unique design of the reconstructed crannog is based on evidence obtained through research and underwater excavations of the Early Iron Age site of Oakbank Crannog off the village of Fearnan in Loch Tay. The materials used match those found on the original site.

Reconstruction began in 1994. A floating perimeter was placed around the spot chosen to build the crannog and a scaffold frame was erected. The majority of the 8-10m long trees being used for the piles are alder, which are very buoyant in the water and easy to manoeuvre. A method was developed for pulling them upright which involved hard pulling by volunteers on the scaffold platform while the pile was steadied by others on a floating raft. While this method worked, it was exhausting for those involved and only 4 or 5 piles could be erected in a day.

The piles were driven into the lochbed by lashing a crosspole perpendicular to the upright pile, the crosspole was then twisted back and forth. The momentum generated, with the weight of the pile, was sufficient to "drive" it into the lochbed to a depth of between 1 and 2 metres, the same depth to which the original 2,600 year old piles had been driven at Oakbank. It is almost certain that this was the method used by the original crannog builders.

168 piles in total were driven in, dozens of crosspieces and floor supports were jointed, pegged, and lashed in place, hundreds of round poles were installed as floor timbers and roof supports, and masses of hazel was woven into hurdles for the house walls. It is easy to understand why the crannog dwellers valued their timber, understood its selection, and practiced coppicing and general principles of conservation and woodland management. By Summer 1997 the structure was completed. The thatched roundhouse has a diameter of 10 metres, surrounded by a walkway 2.5 metres wide and is connected to the shore by a timber causeway 20 metres long.