The first stages of growth of He-based planar defects under H supply have been investigated in (001)-oriented Si. The H atoms were introduced by implantation using the MIAMI facility. Implantations at different temperatures were conducted in the microscope chamber and thus the evolution of He-plates under H implantation was observed in real-time. In situ transmission electron microscopy during the subsequent annealing was also performed. Results show that the growth phenomena are governed by diffusion mechanisms. The kinetic model of Johnson-Mehl-Avrami-Kolmogorov was successfully applied to model the evolution of the diameters of the He-plates either as function of the temperature of annealing or of the fluence. Isotropic coalescence of close defects occurs when the out-of plane tensile stress reaches the yield strength.