FireRock 250 lbs of Mortar

FireRock does not publish a maximum temperature rating or temperature range for the FireRock Adhesive Mortar. Therefore, there is no specific service temperature figure that can be provided.

The FireRock installation instructions describe the material as a low-sand, polymer-modified mortar with heat-resistant additives. It is designed to act as an adhesive bonding the firebox and chimney block together, rather than as a conventional jointing mortar. It is essential for the warranty that this specific mortar is used for installing the firebox; a FireRock fireplace built with any other brand or type of mortar will not be covered under the FireRock warranty. This kit includes 250 pounds of mortar, shipped in 25-pound bags.

FireRock does specify a temperature limit related to installation, not service heat: do not apply the mortar if the temperature is below 40 degrees F, or if it is expected to fall below 40 degrees F within 24 hours after application. Mix with clean water only, to achieve a toothpaste consistency, and never use spirits or anti-freeze agents. Both of these points are detailed in the FireRock installation manual.