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Heat Stop® Refractory Mortar was developed by Robert A. Rucker in the mid-1970’s. Mr. Rucker found that mortars used for fireplace and chimney construction were not high-temperature resistant, were not acid resistant, or were water soluble. Armed with technology from the U.S. industrial refractories industry and determined to succeed, he developed a formulation with the appropriate characteristics that addressed these problems. U.S. and Canadian patents were awarded. Over the years, several additional mortar products were developed and existing products were improved. Today, Heat Stop Refractory Mortar is the industry standard throughout North America for mortar used in high temperature resistant masonry construction.


Formulation is similar to each other and developed for installation of firebrick and clay flue lining in masonry fireplace and chimney installations. They are the product of choice for masonry bread ovens, fireplace and chimney installations (interior or exterior) or where moisture may be present in masonry chimney installation.


HEAT STOP-II is provided in a 10 lb. pail only. (in STOCK)

For estimating purposes approximately 50 lbs. will lay up 100 firebricks (2 ½ inch thick) if joint thickness is 1/16 to 1/8 inch as recommended.

Joint thickness up to 1/2 inch is acceptable with this product and is quite common.

Add clean water (approximately 3/4 to 1 quart) for each 10 lbs. and mix thoroughly. No other additives required.

Cold water works best. Warm water quickens set time. Do not remix or retemper this product as you would with a regular mortar.

Meets and exceeds ASTM C-199, ASTM C-1283, ASTM E-136.

Meets and exceeds all local and national building codes including NFPA-211 and International Residential Codes, (1RC) and International Building Code (1BC) and etc.

Color with masonry mortar color if desired. Follow color manufacturer’s instructions as if using a regular masonry mortar.

Good for applications well over 2,000°F.


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