Kalidas Jethabhai House - CPP course on 'Non-Invasive Testing Methods for Historic Buildings'

The Kalidas Jethabhai House, located in Dharmaj, was one of the sites for a 5-day CPP course on 'Non-Invasive Testing Methods for Historic Buildings'. This structure is presently under the custodianship of Center for Heritage Conservation (CHC), CEPT Research and Development Foundation (CRDF). The investigation's main focus was to identify any potential issues or concerns with the building's structure and material without causing any damage to the historic fabric.

During the assessment, Non-Destructive Tests (NDT) and Minor Destructive Tests (MDT) were employed. Such testing methods are crucial in retaining the maximum historic fabric while providing useful information about the building material and structure. To assess the structure, various tools such as Rebar locator, Rebound hammer, Ultrasonic pulse velocity (UPV), borescope, and moisture meter were used.

A thorough visual assessment of the structure was carried out before employing the NDT/MDT. A tap test was done on the timber elements to check for soundness and identify areas for further testing. Unlike concrete structures, where the RH number can be used to correlate with the compressive strength, the RH number was used as an indicative reference to this specific site for rebound hammer. For UPV, both direct and indirect methods were employed, but the indirect method was unsuccessful due to probe frequency limitations concerning the dimension of the beam.

In addition to the NDT methods, a pinless moisture meter was used to detect the moisture content in masonry and timber elements. This helps in quantifying the visual data and understanding the moisture ingress path, which is critical for identifying areas of potential decay and damage. Furthermore, a borescope was used for the roof visuals since there was a false ceiling and places with cavities.

The investigation revealed critical issues such as the out-of-plane movement of the front elevation, with substantial displacement visible at the corner bracket. The masonry of the front wing was found to be in sound condition, except for the elevation wall, which showed major voids due to decayed bricks and material loss. The beams on the ground floor ceiling slab were severely affected by termite attack, and bending was observed in most of them. Timber bracing on the first floor was found to be in sound condition, while the bracings on the elevation had decayed.

Geometric survey, visual assessment, and non-invasive testing helped makerecommendations to investigate the beams and slab in detail and create access to theroof for further examination. However, due to time constraints during the workshop, theslab was not assessed in detail.

In conclusion, using a combination of different non-invasive testing methods helps investigators gain a comprehensive understanding of a building's condition without causing damage to the historic fabric. These methods are vital for preserving the maximum historic fabric while providing useful information regarding the building material and structure. The recommendations made will help preserve the historic building's structural integrity and historic fabric for future generations.