Equation 2 is the STC equation for clay masonry (ref. 1): For example, consider a masonry cavity wall with an 8in. (203mm) concrete masonry backup wythe ( W = 33 psf, 161 kg/m²) and a 4in. (102mm) clay veneer ( W = 38 psf, 186 kg/m²). When STC tests are performed, the TMS 0302 requires the testing to be in accordance with ASTM E90 ...