Section 2107 addresses concrete footing design and reinforcement. Footings must be provided with reinforcement in both directions unless soil bearing pressure is low. Reinforcement ratio (amount of steel) is typically 0.3-0.5 percent of the concrete cross-sectional area. Bottom mat (lower layer of reinforcement) is placed on chairs to maintain clearance above the soil. Top mat (upper layer) is suspended near the top surface. Development length of reinforcement (anchor distance in concrete) ensures the bar transfers load properly. Bending of reinforcement at corners creates stress concentrations. Minimum cover (distance from reinforcement to concrete surface) is typically 3 inches for footings to protect steel from weather and corrosion.