a multi - layer prefabricated wall panel for modular building and a method for manufacturing the same . the panel comprises a load - bearing and vapor barrier core layer ; an interior insulating and utility installation layer bonded to the inner face of the core layer ; an exterior sheet of a first rigid building material bonded to the interior insulating layer ; and an interior sheet of a second building material bonded to the outer face of said core layer . the method for manufacturing the wall panel comprises the steps of forming a stack of the panel layers with adhesive coating between successive layers and bonding the layers to each other by uniform compressing forces .