Piles shall be of adequate size to resist the applied loads without creating stresses in the pile material in excess of 1,200 psi (8.27 MPa) for piles of southern pine, Douglas fir, oak, or other wood of comparable strength; or 800 psi (5.52 MPa) for piles of cedar, Norway pine, spruce or other wood of comparable strength. Piles of 25 tons (222.5 kN) of capacity or more shall have a minimum 8-inch tip (203 mm) with uniform taper. Piles of less than 25 tons (222.5 kN) of capacity shall have a minimum 6-inch (152 mm) tip with uniform taper. All piles, regardless of capacity, driven to end bearing on bedrock of Classes 1a to 1d and compact gravels and sands of Class 2a shall have a minimum 8-inch (203 mm) tip and a uniform taper. Any species of wood may be used that conforms to ASTM D 25 and that will stand the driving stresses.