Thickness swell (TS) occurs when wood materials absorb moisture and as a consequence create pressure. This study examines the pressure generated following moisture absorption among eight common wood materials using modified methods from ASTM Standard E831 & D1037 to measure the normal swelling pressures as moisture content changed (psi [MPa]). Most test samples expressed maximum pressure after 48 hours. The results showed average maximum pressures were achieved by the medium density fiber board (MDF) (144 psi [0.992 MPa]) while the lowest was gypsum board (5 psi [0.034 MPa]). Comparison of the average maximum values revealed the highest pressures were derived from composite wood products (78 -144 psi [0.538-0.992 MPa], MDF, particle board and oriented strand board) when compared to laminate and solid wood products (57-65 psi [0.393-0.448 MPa], interior and exterior plywood and pressure treated pine). The results can support forensic investigations and the interpretation of building component failures.
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