Refractory mortar differs from regular mortar in that it is designed to resist high temperatures. It is the desired product to use when installing or repairing firebrick in a fireplace, firepit, bake oven, masonry heater, boiler or kiln. It is also the product of choice for installing clay flue lining in a masonry chimney. So when considering an installation or repair in these environments it is best to use a product that meets all the building codes, works well, is fire-safe, and is easy to use.

How is refractory mortar different? Refractory mortar is made from high temperature binders and carefully selected aggregates that will not break down under high temperatures. Heat Stop refractory mortars (Heat Stop 50, Heat Stop II, Heat Stop Premixed, and also Domestic Fireplace Mortar) are considered the industry standard and have been installed all over the world for decades. The dry mix versions of Heat Stop (Heat Stop II or Heat Stop 50) are the most popular and versatile products since they can be used inside or outside, may be colored, they set up overnight, and they have an indefinite shelf. They are naturally light grey color except Domestic Fireplace Mortar which is beige in tone.


Refractory mortar is most often provided in gallon-sized pails, or in larger pails or bags. Premixed refractory mortar is also available in caulking sized tubes.

Bake ovensChimney repairFirepitsHeat stopRefractory mortarRepairing firebrick