James Hardie siding is a unique material blend. It’s 90% sand and cement content, which means it’s fire resistant. It also holds up under conditions that would wreck just about any other kind of siding, such as wood warps, rots, and cracks. Compare this to vinyl siding, which melts and doesn’t have the same authentic look. Even OSB, which is known to be engineered wood siding, cracks under the fluctuation of temperature.