Building a Masonry Heater

 


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8" block foundation with 6" PVC combustion air supply in a slab-on-grade scenario.  If this foundation were in a basement supporting a heater on an upper floor, it would typically run to the bottom of a 12� floor joist. One wall could be eliminated creating a u-shaped alcove of usable space.   Reinforced cast-in-place slab is supported by the block foundation work in the basement and is flush with subfloor.  There�s a 2� clearance to the combustible floor framing from the edge of the slab.  
     
 
Insulated Heat-kit base slab is a cast refractory/ vermiculite mix. Note location of combustion air inlet cut-out and long handled black steel damper that will control air supply.   Assembly begins with two descending side channels in place. They are cast refractory pieces manufactured in our shop. 6" stainless steel combustion air supply is brought up through slab.
     
 
The assembly of connecting flue between the side channels is standard firebrick.   Completing the top of the connecting flue, Dave sets the firebrick in refractory mortar.
     
 
Preparing to place the primary combustion chamber floor on scrap masonry units.   Fred and Dave place the primary combustion chamber floor.
     
 
Construction of the primary combustion chamber uses a double layer of standard firebrick and refractory mortar (view from back of heater).   Bakeoven arch, a cast refractory piece, is in place and construction of secondary combustion zone begins. Steel bands prevent movement during construction. Note opening in bottom section of the side channel that will connect to 8� x 12�chimney flues.
     
 
Front view showing double firebrick combustion chamber. Temporary post at right supports floor load that will later be transferred to the load bearing veneer skin of the heater.   Jeff places the lintels which will support the cast refractory pieces that make up the top of the heater.
     
 
Jeff places the last side channel. Note cut-out for gas slot that pre-warms the chimney for easier starting when the heater is cold.   Dave & Jeff place the first piece of the 3-piece refractory lid. A mix of Portland cement and vermiculite will be poured on top of the lid to provide expansion space for the heater.
     
 
Completed core with heated bench flues laid out on floor. Note the black damper handle projecting through the bench flues. This damper runs back to the short flue that connects to the vertical chimney flue at left. After the chimney is warmed this damper can be closed to direct the hot combustion gases through the bench flues, creating a warm bench.   

Fieldstone veneer work begins on the bench. The entire core will be wrapped in cardboard to allow expansion space between core and veneer. Damper handle visible in this picture controls the combustion air supply directly under the combustion chamber floor.

 
     
 
Core veneer of brick with stone inlays and slate over the bakeoven arch. This veneer was a collaborative effort between the homeowners and Mark, Dave and Jeff. Note chimney flues rising on the left to eventual exit through the roof.    Two-flue chimney construction. The smaller 8�x 8� flue will serve a future woodstove on a lower level.
     
 
Completed heater veneer with slate and brick arch over bakeoven opening.   Paul and Dave with a completed core.