What type of roofing system can leave a white powdery residue when sawed?

The correct answer is gypsum plank. When gypsum boards or planks are sawn, they can produce a white powdery residue, which is primarily composed of gypsum. Gypsum is a mineral that, when cut or sawed, releases fine particles that appear as a white dust. This characteristic is particularly notable during construction or demolition processes where gypsum materials are involved.

The other roofing types do not typically produce a similar residue when cut. Asphalt shingles, while they may release some granules, do not create a powdery substance like gypsum. Metal roofing does not generate any significant residue at all; instead, it may produce metal shavings or filings that are not powdery. Concrete tiles, when cut, tend to chip rather than produce a fine powder, and any dust generated is usually more granular and less fine than the residue from gypsum. Thus, the unique characteristics of gypsum materials set them apart in this context.