Exterior sheathing panel with integrated air/water barrier membrane

A method of manufacturing an exterior sheathing panel with an integrated air/water barrier membrane comprising the following steps:

• preparing a slurry comprising a cementitious material;
• sandwiching the slurry between two cover sheets;
• allowing the slurry to set, and thereby forming a cementitious panel;
• coating the cementitious panel on at least one surface with an integrated air/water barrier membrane formulated with a polymeric binder and calcium carbonate by spray coating, roll coating or flood coating;
• and
• conditioning the coated cementitious panel in an oven, wherein the panel is exposed to at least two different temperature zones.