Introduction
A broch is an Iron Age dry stone round tower unique to Scotland which first appeared around 500 BC. The twin-walled structures, about 8 metres high and 20 metres in diameter and containing an internal spiral staircase were built in both coastal and inland locations mainly within northern Scotland over a period of 500 years.
The twin walls were about 2 metres thick with the outer wall having a 'batter' or outward slope. There was only one very narrow entrance. A permanent wooden framework built inside the broch is thought to have been used to assist in the construction process. Brochs are commonly thought to have been built as defensive structures. There is a long tradition of constructing circular buildings in Scotland; it was probably easier than creating the right angles required for rectangular structures. The finest preserved example of a broch is on Mousa.
Dun Lubnaig
The idea of constructing a section of a broch was first put forward in 1996 by Irwin Campbell in response to a request by the President of the Dry Stone Walling Association (DSWA) for a Millennium project. In 2004, a group of enthusiasts from the DSWA led by Irwin Campbell set out to build a section of a broch without modern tools. The site chosen was in the village of Strathyre. The section was to be 2.5 metres high and be the segment between 7 and 8 o'clock on the clock face. One of the objectives of the exercise was to try to learn how and why brochs were built and to quantify the effort involved.
The approach taken was to try to build the section using the techniques and tools likely to have been used when brochs were being built more than 2000 years ago. First, a centre post and long string were used to mark out the site. The broch was constructed one course at a time with the string being tightened to create the batter on the outer wall. The inner wall was vertical with a plumb bob used to measure verticals. As the stairs were constructed, they were used to assist in the building of the broch. Horizontals were checked using an 'A' frame together with a plumb bob.Hammer stones, usually beach cobbles, were used to 'nibble' or shape stone. These were used in preference to the DSWA specialist hammer.
The photographs were taken during a second phase of construction carried out during June 2006.
Conclusion
The section of the broch built in 2004 required 60 tons of stone and 20 people working for 5 days to build to a height of 2 metres or so. As the broch grew higher, the more difficult the work became. The construction of a full-scale broch would have required 20 people working for a year and using 2500 tons of stone. The whole community, men, women and children are likely to have been involved. Even getting the stone to the site will have been a major logistical problem and it is probable that brochs were located adjacent to a source of stone.
Irwin argues that the length of time required to build a broch required a stable, safe environment and that a broch was therefore more likely to have been erected as a symbol of status and wealth for a local chieftain rather than as a fortress or watchtower.
Related links
The Dry Stone Walling Association is a charitable organisation committed to the preservation of dry stone walls throughout Great Britain and to the training of people in the craft of dry stone walling (drystone dyking in Scotland).The Broch - A Scottish Phenomenon - a beautiful film on DVD about Scotland's historic brochs and the source of most of the content of this web page.