The subject of reinforced concrete is not within the province of this bulletin, but as openings of various widths are required in the walls of most farm structures, a general explanation is given of the reinforcement of lintels or that portion of concrete immediately above an opening, such as a floor or window.

A lintel is a beam, and when a beam bends the lower part is stretched or pulled while the upper portion is compressed. Good concrete will stand great pressure but is not capable of resisting any great pulling or tensile stress. For this reason steel is used in the lower portion to take care of the tensile or pulling force.

It will be found generally satisfactory, where no heavy or concentrated load occurs over an opening and the span is not more than 4 feet, to place two rods three-eighths of an inch in diameter in the bottom of the lintel, so that there will be 1 inch of concrete below them. Two diagonal rods should be placed at each top corner of a window or door, as shown in Figure 18. When the opening is between 4 and 8 feet the rods should be bent up as shown in Figure 19 and when between 8 and 12 feet, three one-half inch rods should be used, two of them being bent.

Barbed wire, old fencing, and scrap or rusty iron is not suitable for reinforcement. Loose rust should be cleaned off the rods and they should be free of grease and oil.