Survey of Traditional Rammed Earthen Buildings in Bhutan
This year will be the third year since the “Networking Core Centers for International Cooperation in the Conservation of Cultural Heritage Project, Preservation of Traditional Buildings in the Kingdom of Bhutan,” which was commissioned by the Agency for Cultural Affairs, started in partnership with the Bhutanese Ministry of Home and Cultural Affairs. Bhutan has many rammed earthen buildings such as residences, and this project aims to preserve those buildings and improve their safety. The Institute has been conducting surveys and studies of traditional Bhutanese construction techniques from the perspectives of architectural history and structural mechanics. The surveys and studies include surveys to examine traditional methods of construction and analyses of the structural strength and earthquake resistance of those buildings. From September 18 to 27, 2014, a fifth field survey was conducted in cooperation with the Institute’s Bhutanese counterpart, the Division for Conservation of Heritage Sites (DCHS) of the Department of Culture under the Ministry of Home and Cultural Affairs.
Prior to this survey, the DCHS had been asked to prepare several test pieces of rammed earth in accordance with instructions regarding the ratios of materials in those pieces. Cores were taken from the prepared test pieces to examine their strength. Results of the inspection verified that walls made of lime and rammed earth provided structural reinforcement. In the past, the strength of these walls depended entirely on the craftsman’s gauging of the size of soil particles and the optimum moisture content of soil. For the inspection, however, DCHS staff members received guidance in operational procedures from the Institute so that these aspects could be quantified by laboratory testing. In addition, the Institute’s structural study team measured microtremors to simulate behavioral characteristics of a temple near Thimphu.
The architectural study team surveyed several residences and ruins that preserve the old style of architecture in a rural community within Paro Dzongkag. This survey aimed to ascertain changes in structural forms and determine their relationship to wall construction techniques. Interviews were also conducted with craftsmen and technicians who are experienced in rammed earth construction in order to gain knowledge. Possible ways to improve methods of construction were discussed with these craftsmen and technicians.
Bhutan experienced heavy rains during the survey. A building that was surveyed last year was found to have already collapsed and new damage to a building that was visited just a few days prior was noted. These examples reveal how fragile these buildings are if they are not properly maintained and these examples highlighted the need to preserve these traditional buildings.