Lift joints are the horizontal joints between lifts or layers of roller-compacted concrete that occur between concrete placing cycles. These joints can vary in thickness from six inches to three feet (15cm to 90cm). In general, contractors try to use the thickest joint possible in order to decrease the overall number of joints present. These joints primarily control the shear strength and seepage of the dam. At lift joints, the coarse aggregate becomes segregated, and thus forms a discontinuity from one lift to another through which water can flow. Another attributing factor to seepage along lift joints is contamination such as dirt from construction equipment, which interferes with the uniformity of the joint and creates an imperfection that allows water to pass through.

Lift joints comprise a crucial part of RCC dam design, because the quality of the bond between successive layers of concrete determines the overall strength and seepage of the dam. Four factors effect the lift joints: condition of the lower RCC surface, time delay between placement of RCC lifts, compaction of the covering roller-compacted concrete, and consistency of the covering RCC.

Too much water on the lower surface leads to poor bond development, and too little water on the lower surface lead to no bond at all. Therefore, the amount of water present is of major importance. The surface must be kept continuously moist, without any ponding water to ensure maximum bond development. Construction equipment often deposits dirt or debris, which decreases the bond strength of the joint. In order to achieve a quality bond, the upper lift must cover the lower lift before the lower lift reaches initial set. If too much time passes between lifts, a cold joint will develop, which does not create a strong bond. The time at which a cold joint develops is dependant upon ambient temperature, RCC mixture proportions, and surface moisture conditions. If a high fly ash content mix, or set retarder is used, the cold joint development time is extended.