This paper reports on the effects of density and core fines content on the transverse permeability, K, of oriented strandboard (OSB), with the aim of using fines generated during the log stranding process to improve mat permeability and possibly press efficiency. Forty-five OSB panels were made in the laboratory containing five levels of fines content (0, 25, 50, 75, and 100%) and compressed to three target density levels (low—450, medium—550, and high—650 kg/m3). Both density and fines content and their interaction significantly influenced Kcore, which increased exponentially with fines content at each density level. Above 75% fines, density level no longer had any significant effect on Kcore, indicating that as the mat is compressed, the presence of fines maintains a more interconnected void system through which gas can pass. The rate of heat transfer to the core was affected by board thickness but contrary to expectations, not by fines content. Fines content did, however, affect the accumulation of gas pressure in the high target density heavily compressed boards; maximum core gas pressure was significantly reduced if core fines content was greater than 50%
