Type I mastics, which have higher values, can be used in all Tile Council of America (TCA) details that cover organic mastics. Type II products, on the other hand, may be used only in a limited manner as described in the TCA Handbook.
The basic water-immersion and shear values illustrate this. Type I mastics, after being immersed in water for seven days, must have a shear value of 50 psi. In comparison, Type II, after water immersion (four cycles at four hours each), needs a shear value of only 20 psi.