Coniferous sawn goods are widely used in construction industry. The quality of round timber deteriorates due to the presence of heartwood rot, which has to be removed in the manufacture of load-bearing structural units. As a rule, rot is removed during the round timber logging. At the same time, healthy sapwood is removed along with that impacted by rot. Therefore, large amounts of quality wood remain in forests. For qualitative ripping of round timber affected by heartwood rot, it is necessary to know the rot shape and size in trunks. The relationship between the round timber cross-sectional dimensions and heartwood rot size along the trunk length is quite accurately described by correlative (allometric) growth equations. As a result of the research, such interrelations were established. Based on the equations obtained, conditional ripping of round log was carried out. As a result, bars for manufacturing I-beams were obtained. They are widely used in lowrise wooden house construction. It was established that the recovery factor was high enough for structural units made of round timber affected by heartwood rot that makes it possible to propose this cutting method for industrial application.