The Public Works Department is preparing a handbook on traditional construction techniques to be adopted for preservation of heritage buildings, based on the experience gained from restoration of a few government buildings.
Officials of the PWD said structures built with lime mortar achieved more strength as they grew old compared to concrete buildings that gained strength only up to 60 years. The department is now involved in sourcing materials to match the original ones used for heritage construction.
K.P.Sathyamurthy, joint chief engineer, PWD (Buildings), who has authored the handbook, said the 100-page book would have elaborate details on the materials sourced from specific locations and complex processes, including Mughal wall plastering or Theervai.
Mughal wall plastering
Wall plastering is the most complex work in heritage conservation and involves nearly eight long process and several coatings. The first one requires mixing of lime and sand and leaving it covered for nearly 15 days before it is applied on the walls. After a three-day drying period, the rest of the meticulous processes are done within a day, with a gap of 15 minutes between each process. While the second process involves applying a mixture of lime and white sand, the third one uses a fine paste of lime and sand.
In a few days, the PWD will use bulls from Perumparai, Tirunelveli to churn the lime mortar instead of a grinder for better compressive strength and longer life. The other processes involve applying of different layers of lime at regular intervals. In the last process, workers apply a mixture of egg white and liquid filtered out of curd for strength and finish. Nearly 11 egg whites and one litre of curd are used for a space of 100 sq. ft. After these seven coatings, labourers use smooth stones and white powder for that perfect, glossy finish
“There are techniques even to apply each coating and materials are tested in the lab. We want to document the intricate process and share it with other professionals. We also plan to include photographs of the work taken up in government buildings like the PWD complex in the handbook,” said C. Kalyanasundaram, superintendenting engineer, Building Centre and Conservation Division, PWD.
The book has also incorporated knowledge of heritage contractor S. Paramasivam, who was involved in the preservation of Madras High Court. A native of Sattur, Virudhunagar district, the 74-year-old learnt the Mughal plastering technique from his father.
"Mixing the correct ratio of materials, particularly lime mortar, for every coating is a challenge," said Mr. Paramasivam, who cherishes memories of former President A.P.J. Abdul Kalam who appreciated his work during a visit to Madras University.
People will be able write to firstname.lastname@example.org for free copies of the handbook in a few months.