Details for the Top of a Masonry Heater

Chimney Connection

With stone or organically shaped heater facings, wood can be TEMPORARILY used to achieve a level backing to create the room for the necessary insulation above the core and a stable and level support for capping slabs.

These photos show anchor plates connecting the metal chimney system to the masonry core for a custom masonry heater. There is one layer of 1/4″ ceramic paper serving as a gasket. Hole locations were marked and 3/16″ holes pre-drilled only to the depth necessary. Four 1/4″x1 1/4″ TapCons with washers are hand-tightened. In general, good to be as gentle on tiles as possible.

The anchor plates shown were custom made by Olympia Chimney to fit to their double wall connector. The Class-A anchor plate is more widely available and will accept Class-A.


The ASTM 1602 Standard requires 2″ of insulation on top of the core. This is a practical perscription which helps to keep heat down in the body of a heater.

We typically build our facing at least 2″ above the core, let that set over night, and then make a mix of perlite and lime the next day which we pack and level into the basin created by the facing. We dry-mix the perlite and lime at a 4:1 ratio and then sprinkle water carefully to achieve a mix which is just uniformly wet enough to form and maintain a ball when packed in your hands.

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