Abstract: A masonry heater (11) confines combustion within a core (15) of refractory material construction. The core includes a primary combustion firebox (18) with fuel access firebox door (20) and a secondary combustion chamber bakeoven (25) over the firebox (18) with a bakeoven access door (26). A tapered throat (35) provides a flue coupling from the firebox (18) to the bakeoven (25). The tapered throat (35) is constructed from a plurality of unmortared replaceable refractory bricks accessible for replacement through the bakeoven door (26). The tapered throat refractory bricks (80,86) are constructed in configurations to rest on each other and provide a structurally self supporting tapered throat structure (55) with at least two sloping sides. The core (15) is constructed with a first course (50) of shelf firebricks (52) providing shelf projections (50,52,54) for supporting the unmortared replaceable refractory bricks (80,86) of the tapered throat structure (55).