Painted surfaces that have come into contact with large volumes of water react in different ways, depending on how long they are immersed and how much water is absorbed.
Typically, for plasterboard, timber and cement sheet, the substrate expands and swells initially, and then shrinks once the water withdraws. Decorative coatings are not designed to withstand total immersion, and blistering issues generally arise due to moisture being trapped in the substrates behind the paint coatings.
Coated steel and other metals corrode when immersed in water, and this process is accelerated if these substrates are subjected to total immersion conditions.
Determine if the surface is sound by conducting an adhesion test on all previously painted surfaces. Prepare affected surfaces by scraping off all loose and flaking paint and ensure surface is dry.