Effects of Fire-Retardant Treatment, Fire Scenarios, and Face Orientation on the Charring Behaviour of Indigenous Timber Species

• Ozovehe A. ALIYU

  Author

• Tasiu A. SULAIMAN

  Author

• Jibrin M. KAURA

  Author

• Idris ABUBAKAR

  Author

• Amana OCHOLI

  Author

The increasing use of timber as a sustainable construction material has heightened the need for improved understanding of its behaviour under fire exposure, particularly for indigenous timber species whose fire performance data remain limited. This study investigates the effects of fire-retardant treatment, fire scenarios, and face orientation on the charring behaviour of selected indigenous Nigerian timber species, namely Erythrophleum suaveolens and Anogeissus leiocarpa. Timber specimens were subjected to three fire exposure scenarios: FT-I, representing the ISO 834 standard fire; FT-II, representing a long-cool parametric fire; and FT-III, representing a short-hot parametric fire. Treated and untreated specimens were exposed under different face orientations, and char depth and charring rate were determined at predetermined exposure intervals. The results showed that charring rate varied with timber species, treatment condition, and fire scenario. Erythrophleum suaveolens consistently recorded lower charring rates than Anogeissus leiocarpa under all investigated conditions. Under FT-I, untreated E. suaveolens and A. leiocarpa recorded mean charring rates of 0.5196 and 0.7160 mm/min, respectively, which decreased to 0.4270 and 0.5782 mm/min after treatment. The highest charring rates occurred under FT-III, while treatment reduced charring rates by 12.21–25.51% across the investigated species and fire scenarios. Face orientation also influenced charring behaviour, with end-grain surfaces showing greater susceptibility to charring than side surfaces. Char depth increased progressively with fire exposure time, while treated specimens exhibited slower char development. Statistical analysis indicated that lognormal, Weibull, and normal distributions provided adequate descriptions of the observed charring rates. The findings demonstrate the potential of the fire-retardant treatment for reducing charring and provide useful experimental data for improving fire protection and fire-safe design of indigenous timber structures.

• 50_Aliyu et al. (2026)

Copyright (c) 2026 Ozovehe A. ALIYU, Tasiu A. SULAIMAN, Jibrin M. KAURA, Idris ABUBAKAR, Amana OCHOLI (Author)

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.