In framed structures, rooms and corridors are formed by placing partitions between structural columns. This practice produces connections between plates which have a column running along the joint. If sound transmission at these joints is to be studied, then the effects of the joint column must be considered. The joint column will resist moments and forces applied by the connected walls. The column cross-section will deform due to the shear forces applied by the plates. In this work these properties of the joint column are used to describe the transmission mechanisms at the joint. Solutions for transmission coefficients at in-line, corner, cross and tee joints are predicted and used to calculate sound transmission between plates. Good agreement is found between measured and predicted results. The joint column increases the transmission loss at high frequencies for transmitted bending and in-plane waves. The transmitted in-plane waves are less important when columns are present. For transmission round a corner (at corner, cross and tee joints) the joint column causes only small changes in transmission loss. There can be a small increase in transmission at low frequencies. For transmission across a joint (at cross and tee joints) the joint column is important when calculating the transmission characteristics and the transmission loss is increased at high frequencies. These effects are also shown to be important for joints where a contained column which exists between connected plates (but is normally ignored) is present. The results show that the contained column increases the transmission loss at high frequencies. © 1994 Academic Press. All rights reserved.