Consider both skin friction and point bearing in drilled shaft design. Calculate total allowable skin friction by multiplying the perimeter of the shaft by the unit value for allowable skin friction derived from Figure 5-1, Figure 5-3, or laboratory data or any combination thereof. Apply a reduction factor of 0.7 to allowable skin friction values derived from Figure 5-1 or from laboratory testing. Do not apply the reduction factor to allowable skin friction values obtained from Figure 5-3. Accumulate skin friction along the length of the shaft beginning at the previously defined disregard depth and continuing down to the tip of the shaft. Calculate total allowable point bearing by multiplying the area of the drilled shaft times the unit value for allowable point bearing derived from Figure 5-2, Figure 5-4, or laboratory data. If softer layers exist within two shaft diameters of the proposed tip, use allowable point bearing values for the softer layers. If drilled shafts are to be tipped in very hard material that is overlain by soft strata, the skin friction contribution of the softer strata may be disregarded in design. However, do not ignore the contribution of significant amounts of competent material in order to tip in rock. In many areas of the state, rock is overlain by thick layers of material that can support considerable loads.