Article about the need to rediscover local limestone for historic building conservation


Aren’t we able to rediscover the indigenous limestone mortar construction technology of Ethiopia?

Limestone Mortar,  as we all might know, consisting primarily of lime and sand, has been used as an integral part of masonry structures for thousands of years and its basic formulation remained unchanged for centuries until the advent of Portland cement or its forerunners. In this regard, ancient countries like Ethiopia have been the home of this technology with some improved chemical additives.

Relics from ancient civilization centers of Ethiopia depict that gypsum and limestone mortar construction technology applied since the earlier civilization periods of the country. Moreover, masonry structures built during the Gondarine dynasty (16th-18th c) witness that limestone mortar technology went through a major growth and transition, whereby, the production and administration process increasingly absorbed techniques traditionally carried out by craftsmen, both from abroad and Ethiopia. Various historical masonry structures (palaces, castles, bridges, church, etc) in the Gondarine dynasty had been constructed with the help of this indigenous technology. The dynasty is the zenith of limestone construction technology in the country.  For instance, the most well known world heritage limestone structures in Ethiopia such as the Guzara Castle, the Susenyos Palace, Denkez Palace, Fasil Castle, Fasil Bath, Debreberhan Sellassie, Kusquam Complex, etc constructed during this period. The unique plastering quality of the then limestone mortar mix helps these structures stand for centuries. 

Getting the status of world heritage property, these structures have a priceless outstanding universal value.  They are an emblem and testimony for the great civilization and urbanization in the history of world. It is obvious that these heritages are source of proud and a medium of spiritual communication among the past, present and future generations. In addition, they are a magnetic field for the socioeconomic development of the region.  

However, these heritages are in the state of deterioration such as disintegrating mortar, cracks in mortar joints, loose red tuffs, damp walls etc resulting from poor conservation works together with other natural and manmade factors.  Hence, unless there is an appropriate repair and restoration to eliminate the source of the problem, mortar deterioration will continue. Nevertheless, the restoration attempts have not been successful as the indigenous masonry materials and methods involving lime technology have been superseded by cement technology among others. This resulted in the total ignorance of the indigenous limestone mortar masonry practice. Again this situation strongly hurt the already the primordial technology transfer system, trial and error method, that uses continuous practice as the only means of acquiring and transferring the technology. These and other reasons facilitated the sharp fall of the technology to the stage of ignorance by the local artisans.   

However, the stake holders came to realize the worsen situation of the problem when cement mortar failed to provide a successful role as a plaster for the restoration of historic lime mortar structures. Conversely, these generations with the advanced indigenous skill have passed without properly transferring this indigenous knowledge to their successors. Hence, currently we have only few artisans with scattered and disorganized indigenous limestone construction knowledge.  This is the basic reason for unsuccessful restoration attempts and recurrent heritage conservation problems that the country is challenged by.  

Hence, in order to maintain the integrity of historic structures, rediscovery and application of traditional lime stone construction technology is a must do business for all concerned stakeholders in and abroad.  

Note: Rediscovery and application of traditional lime technology for heritage conservation must answer the following five basic questions.  How to  

  1. Identifying and analyzing the original and new masonry units to assure the coexistence of the physical and the chemical properties of the historic mortar and the new mortar mixes;
  2. Identify limestone quarry sites and raw material deposit;
  3. Process raw materials and produce sand lime bricks;
  4. Formulate indigenous limestone mortar administration knowledge related to mixing ratio, adulteration, mixing order, and the loosing condition as well as the total volume of water and the time range to use the final mix;
  5. Formulate indigenous limestone mortar administration knowledge to filling depth (thickness), compacting layer, and hardening time for each layer before the next layer is applied;

I believe, answering the above basic questions needs collective effort and cooperation among stakeholders.  Hence, I call up on all concerned professionals/artisans and stakeholders in and abroad take part in the rediscovery and application of the indigenous limestone construction technology of Ethiopia so that we can conserve priceless heritages of all humanity.


This article has been gratefully received from Leul Yohannes

Thanks also to Kibrewosen Negash Bayu for his knowledgeable input on this issue



Published by Gondar's Heritage Conservation Training Centre on