Bowed
Bowing occurs when structural members are insufficient to carry loads, often as undersized members. The structural insufficiency of wooden members, such as joists, beams, posts and rafters can bow or deflect when they cannot support compressive forces and the wood cannot handle the tensile movement imposed by the bowing. If members are exhibiting this structural insufficiency, they warp or crack to relieve the stress. They generally need to be assessed by a structural engineer and reinforced with supplemental structure or be replaced. Bowing, sometimes referred to as bending, can also occur when the ends of horizontal members pull away from their supports as the bottom chords expand in length. Evidence of bowing failure can be seen as compressive cracks from the top, tensile failure from cracks in the bottom or cross-grain, often listed as shear cracks. See Insufficient Structure (IS).