Thickness of Timbers Needed to Equal Strength of Northern Red Oak Timber, 12 inches Thick
Species	Thickness (inches) needed to equal stiffness of Northern Red Oak timber 12 inches thick	Thickness (inches) needed to equal breaking load of Northern Red Oak timber 12 inches thick
E. Cottonwood	13.20	15.55
American Elm	13.29	12.59
Slippery (Red) Elm	12.80	12.60
White Ash	12.17	11.77
Red Maple	12.41	12.45
Northern Red Oak	12.00	12.00
Hackberry	13.81	13.70

Strength Properties of Several Hardwood Species
Species	MOE (x 106 lbf/in2)	MOR (lbf/in2)	Compression Perpendicular to Grain (lbf/in2)	Side Hardness (lbf)
E. Cottonwood	1.37	8,500	380	430
American Elm	1.34	11,800	690	830
Slippery (Red) Elm	1.49	13,000	820	860
White Ash	1.74	15,000	1,160	1,320
Red Maple	1.64	13,400	1,000	950
Northern Red Oak	1.82	14,300	1,010	1,290
Hackberry	1.19	11,000	890	880

Source: USDA-Forest Service. 1999. Wood Handbook - Wood as an Engineering Material. Forest Products Laboratory General Technical Report FPL-GTR-113.