Question 81reads:
Typical 4in by 4in ceramic tiles used as wallcovering in an office building's restrooms should be specified as:
a. vitreous
b. semivitreous
c. nonvitreous
d. impervious

Ballast notes the correct answer to be "a. vitreous." however, according to the ballast text, pg. 43-5, it says impervious is the least absorptive of the 4 options. anyone know why the best answer would not be "d. impervious?" cost?

Thanks,

I suppose impervious tiles would only be necessary in the presence of water, like in a shower environment. Vitreous would be fine as a wall covering.