This study investigates innovative surface coatings’ effectiveness in enhancing spruce wood’s fire resistance (Picea abies spp.). Spruce wood samples were treated with various agents, including oils, waxes, boric acid, commercial coatings, and fire-retardant agents. The evaluation was conducted using the small flame method (EN ISO 11925-2:2020), surface roughness analysis, hyperspectral imaging (HSI), and contact angle measurements. The results demonstrated significant improvements in fire resistance for samples treated with specific coatings, particularly the Burn Block spray and Caparol coating, which effectively prevented flame spread. The analysis revealed that the Burn Block spray reduced the average flame height to 6.57 cm, while the Caparol coating achieved a similar effect with an average flame height of 6.95 cm. In contrast, untreated samples exhibited a flame height of 9.34 cm, with boric acid-treated samples reaching up to 12.18 cm. Char depth measurements and the surface roughness analysis revealed a clear correlation between the type of treatment and the thermal stability of the wood. Hyperspectral imaging enabled a detailed visualisation of surface degradation, while contact angle measurements highlighted the impact of hydrophobicity on flammability. This research provides in-depth insights into the fire-retardant mechanisms of spruce wood and offers practical guidelines for developing safer and more sustainable wood materials for the construction industry.

Fire resistance of wood materials is crucial for the safety and longevity of construction structures, with spruce wood ( Picea abies spp.) being widely used due to its mechanical properties. However, its natural fire resistance is limited, which poses a challenge in the context of fire safety. This study investigates the effects of various treatments and additives on enhancing the fire resistance of spruce wood. The methodology includes testing fire resistance using the small flame test in accordance with relevant standards. The expected results could contribute to improving safety standards in the construction industry, enabling broader and safer application of spruce wood in fire-sensitive constructions. Surface roughness analysis revealed significantly smoother surfaces in treated samples (Sa = 9.03 μm) compared to untreated sawn samples (Sa = 84.54 μm), which contributed to reduced combustion intensity. In small flame tests, untreated samples exhibited visible flames with flame heights up to 13.5 cm, whereas Burn Block treated samples showed no flame development and minimal color changes. Interestingly, burning depth was greater on treated samples, reflecting surface carbonization and the formation of a protective intumescent layer that slowed heat transfer and prevented deeper structural damage.