Firerock Refractory Cement

Firerock Refractory Cement

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FireRock Adhesive Mortar

FireRock Adhesive Mortar is a specially formulated mortar - a low sand polymer modified with heat resistant additives - and is designed to work as a “glue” rather than a typical joint provider. This mortar must be used to install the firebox in order for the FireRock warranty to be valid. It may also be used to install the firebrick, though substitutions are allowed. Substitutions in the firebox will result in a non-compliant unit and will invalidate the FireRock warranty.

  • Weight per bag: 25 lbs
  • Bags per pallet: 96 bags
  • The appropriate number of bags for each fireplace are included with the installation kit
  • Mortar for masonry chimney block must be purchased separately
  • One bag of mortar is needed for every 6 masonry chimney pieces

How to Use Our Mortar


Mix FireRock Adhesive Mortar with clean water according to the instructions on the bag until it results in a “toothpaste” consistency, free of lumps or dry pockets. Be sure it is not too thin or runny to ensure maximum strength. Use only clean water when mixing FireRock Adhesive Mortar. Do not use spirits or anti-freeze agents. Do not apply if temperatures are below 40 °F or will be within a 24 hour period.



  • It is appropriate to use a trowel or grout bag to apply the mortar to firebox and smoke chamber joints.
  • Joints should be COMPLETELY COVERED BY 1/2” - 1” OF MORTAR and the components stacked so as to result in a 1/16” to 1/8” joint.
  • Excess mortar should push (ooze) out and be scraped away.
  • Under normal conditions assembly is cured in 24 to 48 hours.
  • FireRock Adhesive Mortar must be used when building the FireRock fireplace for your FireRock warranty to be valid.



At each level of the firebox, smoke chamber, and masonry chimney it is important to go back and “butter” all joints. This procedure involves a final smoothing of any excess mortar, inside and out, sealing all joints and ensuring a “no-leak” installation.