Abstract: A fire resistant vermiculite composition board comprises, in percent by weight, from 40 to 90% heat expanded vermiculite particles; from 5 to 20% ceramic clay particles; from 10 to 30% hydrated cellulosic gel having a TAPPI drainage time of at least 900 seconds; from 1 to 20% defiberized wood; and from 1 to 20% starch. The vermiculite is in an incompletely expanded condition of a degree predetermined to permit its further expansion upon subsequent exposure to heat. This results in a corresponding expansion of the composition board of which it is a component when the board is exposed to fire, preventing the formation of cracks and insuring continued fire protecting coverage of the area across which the board is applied.