Can a section of wood containing a hard knot be used?

• A. No
• B. Yes, within specified limits.
• C. Only for non-structural sections.
• D. Only if reinforced with metal.

Answer: (B)

Defects like knots are evaluated against approved limits to ensure the wood can carry the expected loads. A knot disrupts grain continuity and creates a stress concentration, which can lower strength and promote cracks as moisture and loads change. A hard knot specifically is a dense region that may not move with the surrounding wood, increasing the risk of cracking under stress. Yet wood with a knot can still be used if the knot size, location, and orientation stay within the limits defined by the applicable spec or design data. If the knot is small, not in a critical load path, and the surrounding wood meets the required grade and moisture conditions, it’s acceptable. Larger knots, or knots in key load areas, would exceed limits and reject the piece.