Lumber is processed wood into uniform sizes for construction and finishing. Timber refers to unprocessed wood in some regions, lumber in others. 80% of lumber comes from softwoods, mainly coniferous species
Firewall is a fire-resistant barrier preventing fire spread. Used between buildings, structures, transformers, or within vehicles. Forms part of passive fire protection systems
Concrete is a composite material made of cement, aggregate, and water. Portland cement is the most common binder, while aggregates include sand and gravel. Concrete hardens through hydration process, forming a stone-like material
Cast iron contains 2-3.5% carbon and 1-3% silicon. White iron forms cementite, grey iron has graphite flakes, ductile iron has spherical nodules. Silicon content determines whether iron forms cementite or graphite
Steel is an alloy of iron and carbon with improved strength and fracture resistance. Carbon content in steel ranges from 0.02% to 2.14% by weight. Steel is denser than pure iron, with density between 7,750 and 8,050 kg/m³
Metal is a naturally occurring chemical element found in Earth's crust. Steel is an alloy of iron with varying carbon content (0.5-1.5%). Steel is not a pure metal but a variation on one