Two mechanisms have been hypothesized to limit the diameter of pancake ice, one due to bending failure and the other due to tensile failure. We conducted two series of laboratory experiments to monitor pancake ice growth from an open water condition in indoor wave tanks. One used urea doped water and the other used salt water with concentration similar to ocean conditions. The final size of the pancakes and the wave conditions are reported here. The laboratory data suggest that in the growth stage, pancake ice floe diameter is limited by tensile failure, in contrast to the bending failure control of floe diameter in ice breakup by waves. The final diameter of the pancake floes is proportional to the wavelength. The proportionality is controlled by wave amplitude and freezing conditions. For wave amplitude A, the proportionality obtained from data agrees closely with the tensile failure theoretical prediction of 1/A0.5.