This Richardson firebox had reached the point where cleaning would not fix it. Years of use had eroded the mortar joints through the lower courses, and the joint at the damper throat had opened up. Under heavy soot, the brick faces had lost surface.
Eroded joints matter because they are the path of least resistance. Heat and combustion gases work into an open joint far more readily than through sound brick, and the damage accelerates once it starts.
What We Found
The lower courses had lost mortar to the point where the joints were recessed rather than flush, and the throat above the firebox had an open joint running along it. Both are findings that would fail a Level 1 inspection, and neither is a candidate for spot pointing once it is that widespread.
Resurfacing and Finish
The firebox was swept and cleaned back to sound material, then resurfaced with a parge coat across the walls and floor. Parging seals every joint as one continuous surface, so there is no line of individual repairs each free to move on its own.
The finish was scored to follow the original brick coursing rather than left as a flat slab. It takes longer and it is the difference between a firebox that reads as repaired and one that reads as patched. The masonry work is finished level with the existing hearth.
