Current design criteria for timber beams are often governed by calcula
ting shear strength rather than bending strength. However, bending is
often observed as the controlling factor in real structures and experi
mental studies. This report describes a design procedure based on pred
icting whether bending or shear will control the design and designing
the member for that consideration. The prediction is based on comparin
g the ratio of maximum bending and shear stresses to experimentally de
termined bending and shear strengths. Stresses are based on load and s
upport conditions and span/depth ratios. A lower limit bending-to-shea
r stress ratio of 10 is recommended for design on the basis of a lower
bound fit to experimental strength values. For this stress ratio, typ
ical designs for most load and support conditions will result in bendi
ng-controlled designs that do not require shear calculations. Shear wi
ll control the design for a simply supported span with a concentrated
load near one support or for a span with a short overhang having a con
centrated or uniform load. This approach is limited to unsplit and unn
otched beams. Design considerations for notched beams and shear at con
nections are outside the scope of this report.