Gypsum board/intumescent material ceiling boards

A gypsum board/intumescent material ceiling comprising:

• spaced apart parallel framing members;
• a plurality of gypsum boards secured to the framing members by metal fasteners;
• each gypsum board having a gypsum core;
• the gypsum core having first and second major surfaces;
• the first and second major surfaces each having a width and a length;
• the first and second major surfaces having facings thereon;
• and the first major surface being an upper side of the gypsum board abutting the framing and the second major surface being an underside of the gypsum board facing a room interior;
• and
• a fire-resistive barrier, the fire-resistive barrier being a layer of intumescent coating material applied to one of the major surfaces of each of the gypsum boards;
• the intumescent coating material including a carrier, expandable graphite and a corrosion inhibitor to provide a corrosion inhibiting layer on surfaces of the metal fasteners with which the intumescent coating material comes in contact;
• the corrosion inhibitor being selected from a group consisting of sodium hexa meta phosphate, sodium meta phosphate, sodium silicate and other sodium based phosphate compounds and the carrier including between about 200 and about 10,000 parts per million corrosion inhibitor;
• the intumescent coating material having a pH between 8.0 and 8.5 to reduce corrosive properties of the intumescent coating material and provide a chemical environment conducive to the forming of the corrosion inhibiting layer by the corrosion inhibitor;
• and the fire-resistive barrier being coextensive in width and length with the width and length of the second major surface of the gypsum board.