Methodology for monitoring cracking in historical wattle-and-daub ceiling slabs using Infrared Thermography

Wattle-and-daub ceiling slabs, common in Europe until the early 20th century, are highly prone to cracking and plaster detachment. This study assesses the use of active, quantitative infrared thermography to detect and characterize such cracks, distinguishing between superficial and through-thickness damage by analyzing thermal responses to low-intensity heating, while maintaining a workflow consistent with realistic diagnostic practices in heritage environments. The approach combines step heating and lock-in thermography to obtain qualitative anomaly maps and depth estimates. It introduces a new acquisition protocol that utilizes temporary room depressurization to enhance thermal contrast, along with an improved dynamic signal-analysis algorithm. The outcome is a reliable, contact-free procedure for monitoring degradation in wattle-and-daub slabs, suitable for large or hard-to-access areas, supporting conservation planning.