To keep "Ryūjō"s weight to 8,000 metric tons, the hull was lightly built with no armor; some protective plating was added abreast the machinery spaces and magazines. She was also designed with only a single hangar, which would have left an extremely low profile (there being just of freeboard amidships and aft). Between the time the carrier was laid down in 1929 and launched in 1931, the Navy doubled her aircraft stowage requirement to 48 in order to give her a more capable air group. This necessitated the addition of a second hangar atop the first, raising freeboard to . Coupled with the ship's narrow beam, the consequent top-heaviness made her minimally stable in rough seas, despite the fitting of Sperry active stabilizers. This was a common flaw amongst many treaty-circumventing Japanese warships of her generation.