Applies a single Factor of Safety to the material's ultimate strength to determine "allowable" stresses. Loads: Uses actual expected (unfactored) service loads.
Modern, reliability-based method that uses statistical probability . Structural wood design: ASD/LRFD
Remains the historical standard for wood and is widely used due to its simplicity and the extensive existing library of hardware catalogs based on ASD. Load and Resistance Factor Design (LRFD) Applies a single Factor of Safety to the
Traditional, deterministic method based on elastic design . Structural wood design: ASD/LRFD
Applies separate factors to both loads (Load Factors) and material strength (Resistance Factors).
"Factored" loads increase the design burden based on the uncertainty of the load type (e.g., higher factors for live loads vs. dead loads).